Dissertations / Theses on the topic 'Translationally controlled tumour protein'

Background: Pulmonary arterial hypertension (PAH) is a multifaceted disease characterized by elevated pulmonary arterial pressure, right ventricular hypertrophy, and a poor prognosis. Pathological hallmarks of PAH include pulmonary vascular remodelling, pre-capillary arterial obliteration, and plexiform lesions. Over the past 15 years, pulmonary endothelial cell (EC) apoptosis has been repeatedly implicated as a key trigger of occlusive arterial remodelling in PAH. While it has been hypothesized that pulmonary EC apoptosis gives rise to the emergence of growth-dysregulated, apoptosis- resistant ECs involved in arterial remodelling, the molecular mechanisms linking these two events has not yet been fully elucidated. Recently, our lab identified translationally controlled tumour protein (TCTP) as one of several significantly dysregulated proteins in culture-derived blood-outgrowth endothelial cells (BOECs) isolated from hereditable PAH (HPAH) patients harbouring mutations in the gene encoding for bone morphogenetic protein receptor type 2. Immunohistological analyses indicated that TCTP expression was associated with intra-luminal pulmonary ECs and inflammatory cells in the remodelled vessels of both human PAH patients and SU5416 rats. Furthermore, TCTP silencing abrogated excessive HPAH BOEC proliferation and promoted apoptosis in vitro. Hypothesis: We hypothesized that TCTP represents a central molecular mechanism linking pulmonary arterial EC damage and apoptosis to the emergence of growth- dysregulated lung vascular cells and complex arterial remodelling in PAH.Purpose: The purpose of the present thesis was to examine the effects TCTP inhibition on EC survival and TCTP abundance in vitro as well as on pulmonary hemodynamic changes and arterial remodelling in vivo using a well-validated rat model of severe PAH. Methods: Inhibition of TCTP was accomplished using two TCTP small molecule inhibitors, sertraline and thioridazine. In vitro, rat lung microvascular ECs (RLMVECs) were exposed to thioridazine and assayed for TCTP abundance, survival, and markers of apoptosis. In vivo, PAH was induced in male Sprague Dawley rats using SU5416 combined with 3 weeks of chronic hypoxia (SU/CH). After 4 weeks, right ventricle systolic pressure (RVSP) was measured by direct catheterization and osmotic pumps containing either thioridazine or sertraline were implanted subcutaneously. Following 3 weeks of small molecule delivery, RVSP was re-evaluated, cardiac function/structure was determined using transthoracic echocardiography, and histological analyses of vascular remodelling and inflammation were performed. Results: Our in vitro experiments demonstrated that thioridazine was able to significantly down-regulate TCTP levels and induce an apoptotic phenotype in RLMVECs. In the SU/CH rat model of severe PAH, both thioridazine and sertraline failed to have any effect on pulmonary hemodynamics, right ventricle structure/function, or vascular remodelling. Moreover, neither small molecule was able to detectably down-regulate TCTP levels in the lungs of SU/CH rats. Immunofluorescence staining revealed that TCTP expression occasionally corresponded with the expression of macrophage/monocyte marker CD68 in the lungs of SU/CH rats, consistent with its expression by inflammatory cells; however, no significant differences were found in adventitial cell clearance in the presence or absence of the inhibitors. Conclusions: Our findings support previous reports that thioridazine is able to significantly down-regulate TCTP and induce apoptosis in vitro. In contrast, both small molecule inhibitors failed to down-regulate lung TCTP levels or have any beneficial effects on the progression of PAH in SU/CH rats.

Introduction: Diabetes affects more than 346 million individuals worldwide. Some 90% of diabetics have type 2 diabetes mellitus, which is frequently associated with obesity and hyperlipidemia as well as hyperglycaemia. There is ample evidence that fatty acids become toxic (lipotoxicity) when present at elevated concentrations for prolonged periods of time, although mechanisms are still not fully elucidated. Current diabetic medications do not tackle the underlying issue of β-cell death. New therapeutic strategies to more effectively combat and early deterioration of the β-cell mass and function due to lipotoxicity are thus required. Translationally Controlled Tumour Protein (TCTP) has been identified in a wide range of eukaryotic organisms and linked to many diverse cellular processes including acting as an anti-apoptotic protein. Ideally human islets of Langerhans would be used to investigate diabetes however they are not practical to use due to only being acquirable from cadavers. Rodent islets are more readily available however keeping the rodents require a lot of money, time and a license to ensure they are being cared for correctly. Monolayer cell lines have been created for the use in basic research which can be grown in a suspension forcing the cells to attach to each other forming 3D structures commonly referred to as pseudo-islets, have shown some promising results. Aims: (1) establishing an imaging-based assay for analysing characteristic changes in pancreatic β-cells lipotoxicity, (2) investigate the effect of TCTP in connection with lipotoxicity and (3) investigate possible alternatives to using cultured monolayer cells or isolated islets of Langerhans for diabetes research. Methods: MIN6, INS-1, HIT-T15, alpha TC 1 clone 6 cells and Hans-Wistar rat islets were incubated with were incubated with forskolin, exendin-4, thapsigargin, palmitate and oleate/palmitate (1:1) mix under stimulatory glucose conditions for 8, 24 or 48h to investigate lipid accumulation and/or protein changes. Lipid accumulation and cell death was investigated using ImageXpress 5000a and confocal microscopy. Changes in protein expression were investigated using immunoblots using a mouse monoclonal anti-TCTP antibody. Equal amount of protein was loaded into each lane and glyceraldehyde-3-phosphate-dehydrogenase (GAPDH) or extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) were used as internal controls. Changes in TCTP mRNA expression levels were investigated using TaqMan® with real-time PCR. Pancreatic spheroid formation was investigated using MIN6 and INS-1cells via three methods: agarose overlay, hanging drop/methyl cellulose, and confocal microscopy. Conclusions: Lipid accumulation could successfully be tracked in monolayer cells and islets of Langerhans. Proteomic and biochemical approaches revealed that TCTP level is regulated by glucose, palmitate and exendin-4. Regulation of TCTP by glucose and exendin-4 is cyto-protective. In contrast, high concentration of palmitate causes cell stress, reduction in TCTP protein level and consequently reduced cell viability. This study demonstrated that the cytotoxic effects of palmitate are at least in part mediated by the inhibition of the production of the anti-apoptotic protein TCTP which is reversed with the addition of exendin-4. In contrast, TCTP mRNA was found to be elevated in response to high level of fatty acids both in MIN6 cells and Zucker fatty rat islets of Langerhans suggesting that β-cells try to compensate for the reduced translation of TCTP. The investigation in to an alternative method for spheroid creation failed to produce complete spheroids but a number of areas for future improvements were identified.

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-09-13T16:56:22Z No. of bitstreams: 1 texto completo.pdf: 2092738 bytes, checksum: 991c21e0ecefbc7be1990a39f757c9bb (MD5)
Made available in DSpace on 2017-09-13T16:56:22Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2092738 bytes, checksum: 991c21e0ecefbc7be1990a39f757c9bb (MD5) Previous issue date: 2016-11-21
Conselho Nacional de Desenvolvimento Científico e Tecnológico
Translationally controlled tumor protein (TCTP) é uma proteína amplamente distribuída em eucariotos. Ela está envolvida na regulação de processos básicos como progressão do ciclo celular, crescimento celular, proteção contra estresses e apoptose. Durante a infecção de tomateiro (Solanum lycopersicum) e Nicotiana benthamiana pelo potyvírus Pepper yellow mosaic virus ocorre aumento dos níveis de seu mRNA. Plantas silenciadas para TCTP acumulam menos vírus do que plantas selvagens, mostrando que esta proteína é importante para a infecção por potyvírus. Neste trabalho, o envolvimento da TCTP na infecção por potyvírus foi analisado detalhadamente utilizando-se o potyvírus Turnip mosaic virus (TuMV). Em plantas de N. benthamiana silenciadas para TCTP também ocorre uma diminuição no acúmulo do TuMV quando comparado com plantas não silenciadas. Além disso, plantas superexpressando TCTP de maneira transiente acumularam mais vírus do que plantas controle, confirmando o efeito positivo desta proteína na infecção por diferentes espécies de potyvírus. Para analisar a localização subcelular de TCTP no contexto da infecção, TCTP fusionada a GFP foi co-expressa com TuMV/6K2:mCherry. TCTP co-localiza-se com as vesículas replicativas e com estrutura a globular perinuclear tipicamente observada em células infectadas. O fracionamento de proteínas celulares demonstrou que TCTP está predominantemente na fração solúvel e uma pequena porção se associa com membranas, tanto em plantas sadias quanto em plantas infectadas. A co- localização com vesículas marcadas por 6K2 e a presença de TCTP em frações membranosas da célula sugerem um possível envolvimento desta proteína na replicação viral. Para verificar esta hipótese, protoplastos obtidos a partir de plantas silenciadas para TCTP foram infectados com TuMV e com o mutante TuMV VNN , o qual não é capaz de replicar-se. Os resultados demonstraram que o acúmulo de TuMV é reduzido em protoplastos silenciados, indicando que TCTP é necessária para a replicação. O acúmulo da proteína TCTP durante a infecção também foi avaliado. A infecção viral induz o aumento dos níveis de mRNA mas não de proteína, sugerindo que o mRNA que codifica TCTP atue na replicação. Desta forma, foi analisado se expressão de um RNA não traduzível de TCTP possui efeito sobre a infecção viral. Os resultados mostraram que apenas a expressão de um RNA traduzível é capaz de aumentar a infecção viral, indicando que a proteína TCTP, ou que a tradução se seu mRNA, é importante para a replicação viral.
The translationally controlled tumor protein (TCTP) is widely distributed among eukaryotes. It is involved in the regulation of basic processes such as cell cycle progression, cell growth, stress protection and apoptosis. During tomato (Solanum lycopersicum) and Nicotiana benthamiana infection by the potyvirus Pepper yellow mosaic virus, an increase of TCTP mRNA levels was observed. Plants silenced for TCTP accumulate fewer viruses than control plants, showing the importance of that gene for potyvirus infection. In this work, TCTP involvement in potyvirus infection was analyzed in details using the potyvirus Turnip mosaic virus (TuMV). N. benthamiana plants silenced for TCTP accumulated fewer viruses than non-silenced plants. In addition, plants overexpressing TCTP transiently accumulated more viruses than control plants, confirming that TCTP has a positive effect on infection by different potyviruses. To study TCTP subcellular localization in potyvirus infected plants, TCTP fused to GFP was co- expressed with TuMV/6K2:mCherry. Confocal analysis has shown that TCTP co- localizes with 6K2-tagged structures such as replicative vesicles and the perinuclear globular structure that is typically observed in potyvirus-infected cells. Cellular fractioning demonstrated that TCTP is mainly present in the soluble fraction but is also associated with membranes. The co-localization of TCTP with 6K2-tagged vesicles and its presence in cellular membranous fractions suggests a possible involvement of TCTP in virus replication. To test this hypothesis, protoplasts obtained from TCTP silenced plants were infected with TuMV and its mutant TuMV VNN , which is defective for replication. The results showed that TuMV accumulation is reduced in silenced protoplasts, indicating that TCTP is necessary for replication. TCTP accumulation during infection was also analyzed. Viral infection induces TCTP mRNA expression, but not protein accumulation, suggesting that the TCTP mRNA and not the protein has a role in viral infection. To check this, we expressed a non-translatable form of TCTP RNA in plants and analyzed its effect in virus accumulation. The results showed that only the expression of a translatable RNA resulting in protein production is able to increase virus infection, indicating that the protein and/or the translation of TCTP is important for potyvirus replication.

Hepatocellular carcinoma (HCC) is the most common tumors worldwide. In contrast to other cancers, the prognosis of HCC is extremely poor, with less that 5% of 5-year survival rate worldwide. From our previous studies, we isolated Chromodomain Helicases/ATPase DNA binding protein1-Like (CHD1L) gene from chromosome 1q21, and characterized it as a specific oncogene in HCC. By using 2D-PAGE and MALDI-TOF mass spectrometry approach, Translationally Controlled Tumor Protein (TCTP) was identified as a CHD1L target, which was preferentially expressed in CHD1L-transfected cells. TCTP is a highly conserved protein and expressed in almost all mammalian tissues. It has been reported that TCTP interacts with microtubules in a cell-cycle-dependent manner, and functions as a prosurvival factor and inhibiting apoptosis. To better understand the molecular mechanisms of HCC progression, the effect of TCTP overexpression in HCC and the mechanism by which TCTP regulated cell-cycle progression were elucidated in this study. CHD1L is a unique oncogene belongs to SNF2-like subfamily. Mechanistic studies found that CHD1L protein directly binds to the promoter region (nt -733 to -1,027) of TCTP and activated TCTP transcription. Investigation of clinical HCC specimens found that overexpression of TCTP was not only significantly associated with the advanced tumor stage (P = 0.037) and overall survival time of HCC patients (P = 0.034), but also an independent marker associated with poor prognostic outcomes. Functional studies demonstrated that TCTP has tumorigenic abilities and overexpression of TCTP contributed to the mitotic defects of tumor cells. Further mechanistic studies demonstrated that TCTP promoted the ubiquitin-proteasome degradation of Cdc25c during mitotic progression, which caused the failure in the dephosphorylation of Cdk1 on Tyr 15 and decreased Cdk1 activity. The consequence of chromosome missegregation and mitotic catastrophe results in aneuploidy, which is frequently observed in cancer. In addition, the correlation between TCTP overexpression and metastatic potential of HCC was elucidated by examined the expression levels of TCTP using a tissue microarray (TMA) containing 60 pairs of primary HCCs and their matched metastases. Further studies demonstrated that overexpression of TCTP shows high incidence of extrahepatic metastasis and positive correlation was found between TCTP and MMP-2 or MMP-9 (Spearmen correlation coefficient=0.466, and 0.352, respectively, P<0.001 for both). In vitro functional studies showed that TCTP protein associated with promoter regions of MMP-2 and MMP-9 and activates their transcriptions. Molecular analyses revealed that TCTP served as a JunD coactivator and formed complexes with JunD and bind with consensus AP-1 sites on MMP-2 and MMP-9 promoters to enhance their expression in HCC cells. More importantly, high co-expression of TCTP and MMP-2 or MMP-9 was significantly associated with poor disease-free survival (log rank= 8.146, and 11.677 respectively, P =0.017 and 0.003 respectively). In summary, two novel molecular mechanisms (CDH1L/TCTP/Cdc25C/Cdk1) and (TCTP/JunD/MMP-2, MMP-9) were revealed during HCC progression and metastasis. Also, the prognostic value of TCTP and MMP-2 or MMP-9 coexpression for HCC was highlight in this study.
published_or_final_version
Clinical Oncology
Doctoral
Doctor of Philosophy

TCTP est une protéine de 20 kDa que l’on retrouve souvent sous forme de dimère. Elle est fortement conservée dans la phylogénie et on la trouve dans les levures, les plantes, les invertébrés et les mammifères. Elle est localisée dans tous les compartiments de la cellule : noyau, cytoplasme, et membranes. Il s’agit d’une protéine très abondante dans des cellules souches ainsi que des cellules en croissance exponentielle, y compris les cellules tumorales. Sa fonction principale est celle d’une « protéine de survie ». TCTP a été décrite comme interagissant avec de multiples protéines dont p53, MDM2, Bcl-xL et TSAP6. Le but de mon travail est de permettre de mieux caractériser ces fonctions de TCTP et pour cela, nous avons étudié ses interactions in vitro et surtout, in vivo, dans différents modèles génétiques chez la souris
TCTP is a 20 kDa protein frequently encountered as a dimer. It is highly conserved through phylogeny and is present inn yeast, plants, invertebrates and mammals. It is localized in all compartments of the cell: nucleus, cytoplasm, membranes. This protein is highly abundant in stem cells and during the exponential growth, including in cancer cells. It mainly functions as a survivor factor. TCTP has been described as interacting with multiple proteins, including p53, MDM2, Bcl-xL and TSAP6. The purpose of my work is to better characterize these functions of TCTP; we therefore studied its interactions in vitro, but mostly in vivo, using different murine genetic models

La thématique du laboratoire de l’équipe d’Adam Telerman porte sur la réversion tumorale, un processus rare au cours duquel les cellules cancéreuses perdent leur phénotype malin, et deviennent des cellules dites révertantes. Plusieurs protéines clefs impliquées dans cette transformation ont été mises en évidence, dont TCTP (Translationally Controlled Tumor Protein). La protéine TCTP est également impliquée dans la régulation de l’apoptose en interagissant et en renforçant l’activité anti-apoptotique de Mcl-1 et de Bcl-xl, deux protéines appartenant à la famille des Bcl-2. Ce projet s’attache à comprendre en termes moléculaires le mode d’action de TCTP au cours de l’apoptose
Adam Telerman’s team research focuses on tumor reversion, a rare process in which cancer cells lose their malignant phenotype, and therefore become revertant. Many key proteins were showed to be involved in this transformation, including TCTP (translationally Controlled Tumor Protein). TCTP protein is also involved in apoptosis regulation by interacting and strengthening the anti-apoptotic activity of Mcl-1 and Bcl-xl, two proteins from Bcl-2 family

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2018-08-24T18:20:21Z No. of bitstreams: 1 texto completo.pdf: 484015 bytes, checksum: fda75b7a7bc67b7a6301406613010fcd (MD5)
Made available in DSpace on 2018-08-24T18:20:21Z (GMT). No. of bitstreams: 1 texto completo.pdf: 484015 bytes, checksum: fda75b7a7bc67b7a6301406613010fcd (MD5) Previous issue date: 2017-07-26
Fundação de Amparo à Pesquisa do Estado de Minas Gerais
Os vírus são as formas de vida mais abundantes e geneticamente diversas conhecidas em nossa biosfera. Para infectar hospedeiros com sucesso, os vírus manipulam componentes celulares do hospedeiro, recrutando fatores do hospedeiro necessários para replicação, infeção e transmissão. Além disso, os vírus precisam suplantar diversas estratégias de defesa do hospedeiro levando a um complexo mecanismo de coevolução que envolve diversas interações. Diferentes vírus podem interagir com componentes celulares do hospedeiro de forma semelhante. Foi demonstrado que a presença da proteína translationally controlled tumor protein (TCTP) é necessária para o estabelecimento de uma infecção eficiente por potyvírus. TCTP é uma proteína multifuncional encontrada em quase todos os eucariotos envolvida no crescimento celular, homeostase de íons, reparo de danos no DNA e possuí atividade anti-apoptótica. Apesar de inúmeros estudos com TCTP, o envolvimento desta proteína na infecção viral ainda não é totalmente compreendido. Devido a sua diversidade funcional, é possível imaginar que TCTP possa ser um fator do hospedeiro envolvido em infeções causadas por vírus de diferentes grupos. Desta forma, neste trabalho, foi avaliado o efeito de TCTP na infecção por begomovírus. Para isso, plantas de Nicotiana benthamiana com TCTP silenciada por VIGS foram utilizados para estudar o efeito da TCTP na infecção pelo begomovírus Tomato yellow spot virus (ToYSV). O silenciamento de TCTP levou a um maior acúmulo de vírus, sugerindo que TCTP é um fator do hospedeiro envolvido no processo de defesa á infecção viral. Além disso, o mRNA de TCTP é altamente estruturado em mamíferos e está relacionado com a indução de resposta a infecções por diferentes vírus. Por ser um mRNA altamente estruturado é razoável supor que o mRNA de TCTP pode ser alvo do processo de silenciamento pós transcrisional da planta levando à produção de pequenos RNAs de interferência (siRNAs) através da clivagem por proteínas Dicer e os siRNAs gerados podem regular a expressão de genes endógenos do hospedeiro. Desta forma, foi realizada uma análise in silico para avaliar os possíveis siRNAs gerados a partir do silenciamento do mRNA de TCTP e os possíveis alvos desses siRNAs. Genes que podem estar envolvidos em infecção viral, como aqueles que codificam proteína kinases, proteínas envolvidas na via de ubiquitinação, fatores de transcrição e tradução e proteínas de ligação ao cálcio foram alguns dos genes identificados como possíveis alvos destes siRNAs.
Viruses are the most abundant and genetically diverse life forms known in our biosphere. To successfully infect hosts, viruses manipulate host cellular components, recruiting host factors necessary for replication, infection, and transmission. In addition, viruses need to supplant various host defense strategies, leading to a complex coevolution mechanism involving virus-host interactions. Different viruses can interact with host cell components similarly or even antagonistic. The presence of the protein translationally controlled tumor protein (TCTP) has been shown to be necessary for the establishment of an efficient potyvirus infection. TCTP is a multifunctional protein found in almost all eukaryotes and is involved in cell growth; ions homeostasis; DNA damage repair and anti-apoptotic activity. Despite numerous studies with TCTP, the involvement of this protein in viral infection is not yet fully understood. Due to its functional diversity, it is possible to imagine that TCTP may be a host factor involved in infections caused by viruses of different groups. Thus, in this work, the effect of TCTP on begomovirus infection was evaluated. Nicotiana benthamiana plants silenced for TCTP by VIGS experiments were used to study the effect of TCTP expression on infection by the begomovirus Tomato yellow spot virus (ToYSV). TCTP silencing led to higher accumulation of the virus, suggesting that TCTP is a host factor involved in viral infection defense process. Furthermore, TCTP mRNA is highly structured in mammals and is related to the induction of defense response to different viruses. Because it is a highly structured mRNA, it is reasonable to assume that TCTP mRNA may be the target of the plant post transcription gene silencing mechanism, leading to the production of small interfering RNAs (siRNAs) by the cleavage of Dicer proteins and the siRNAs generated might regulate the expression of host endogenous genes involves in virus infection. In silico analysis was performed to evaluate the possible siRNAs generated from the silencing of TCTP mRNA, and the respective targets of this siRNAs. Genes involved in viral infection, such as those encoding protein kinases, proteins involved in the ubiquitination pathway, transcription and translation factors, and calcium binding proteins were some of the genes identified as possible targets of these predicted siRNAs.

Made available in DSpace on 2014-06-11T19:26:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-09-28Bitstream added on 2014-06-13T19:12:49Z : No. of bitstreams: 1 carvalho_m_me_botib.pdf: 857762 bytes, checksum: 6884bf144951c5e915d6a1c0a0ca3e5c (MD5)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
O gene que codifica a TCTP (Translationally Controlled Tumour Protein) está presente em todos os eucariontes e o seu produto está envolvido em diferentes processos celulares. Embora bem caracterizada em mamíferos, poucos são os trabalhos disponíveis na literatura relacionados à análise da TCTP em plantas. No presente trabalho, a expressão do gene que codifica a TCTP em tomateiros foi analisada em situações de estresse biótico e abiótico. No estresse abiótico, as plantas de tomate foram submetidas a dano mecânico nas folhas, e essas coletadas após 4, 8 e 12 horas. No estresse biótico, duas espécies virais foram inoculadas mecanicamente nas plantas de tomate, o Cucumber mosaic virus (CMV) e o Pepper Yellow Mosaic Virus (PepYMV), respectivamente, e as folhas sistemicamente inoculadas foram coletadas após 25 dias. Um aumento na expressão da TCTP foi constatado em resposta ao estresse biótico, sendo de 1,3x em relação ao controle não inoculado na infecção pelo CMV, e de 1,4x na infecção pelo PepYMV. No estresse mecânico, o pico de expressão ocorreu após 4 horas com um aumento de 3,4x em relação ao controle não tratado, com posterior redução nos demais tempos. Adicionalmente, plantas transgênicas de tabaco capazes de superexpressar a TCTP de tomate foram geradas a fim de determinar o papel dessa proteína na infecção pelo PepYMV. Quando as linhagens transgênicas geradas foram inoculadas com o PepYMV observou-se, aos 14 dias após a inoculação (DAI), um aumento na concentração viral (1,8x) em relação às plantas de tabaco não transformadas, sendo o mesmo verificado aos 21 DAI (1,6x). Essa diferença, entretanto, não foi mais observada aos 28 DAI. Esses dados confirmam a relação funcional da TCTP com a resposta de defesa das plantas aos estresses bióticos e abióticos
Not available

Orientador: Ivan de Godoy Maia
Banca: Fábio Tebaldi Silveira Nogueira
Banca: Jomar Patricío Monteiro
Resumo: O gene que codifica a TCTP (Translationally Controlled Tumour Protein) está presente em todos os eucariontes e o seu produto está envolvido em diferentes processos celulares. Embora bem caracterizada em mamíferos, poucos são os trabalhos disponíveis na literatura relacionados à análise da TCTP em plantas. No presente trabalho, a expressão do gene que codifica a TCTP em tomateiros foi analisada em situações de estresse biótico e abiótico. No estresse abiótico, as plantas de tomate foram submetidas a dano mecânico nas folhas, e essas coletadas após 4, 8 e 12 horas. No estresse biótico, duas espécies virais foram inoculadas mecanicamente nas plantas de tomate, o Cucumber mosaic virus (CMV) e o Pepper Yellow Mosaic Virus (PepYMV), respectivamente, e as folhas sistemicamente inoculadas foram coletadas após 25 dias. Um aumento na expressão da TCTP foi constatado em resposta ao estresse biótico, sendo de 1,3x em relação ao controle não inoculado na infecção pelo CMV, e de 1,4x na infecção pelo PepYMV. No estresse mecânico, o pico de expressão ocorreu após 4 horas com um aumento de 3,4x em relação ao controle não tratado, com posterior redução nos demais tempos. Adicionalmente, plantas transgênicas de tabaco capazes de superexpressar a TCTP de tomate foram geradas a fim de determinar o papel dessa proteína na infecção pelo PepYMV. Quando as linhagens transgênicas geradas foram inoculadas com o PepYMV observou-se, aos 14 dias após a inoculação (DAI), um aumento na concentração viral (1,8x) em relação às plantas de tabaco não transformadas, sendo o mesmo verificado aos 21 DAI (1,6x). Essa diferença, entretanto, não foi mais observada aos 28 DAI. Esses dados confirmam a relação funcional da TCTP com a resposta de defesa das plantas aos estresses bióticos e abióticos
Abstract: Not available
Mestre

Period 2 (Per2) is a core circadian factor responsible for its own negative regulation. It operates in the circadian clock, which affects multiple biological functions such as metabolic rate, hormone release, and core body temperature. The Per2 protein functions directly with factors in other biological functions such as tumor suppression, immune system, and metabolism. In many cases, the Per2 deficiency caused by disrupted expression is sufficient to create severe abnormalities in many of the mentioned functions. The sequence contains several domains and motifs in Per2 that are traditionally involved in protein interactions which suggests that Per2 serving a regulatory role by effecting downstream biological roles dependent on Per2 stability. In this work, we perform a two-hybrid screening assay using the C-terminal region of human Per2 and identified an extensive number of interactors. Utilizing a genetic ontology program, we assorted the list of clones into groups of proteins that are biologically relevant or operated in similar function. Through this program, we validated the two-hybrid screening by the clusters of biological function already attributed to hPer2 and identified new putative biological functions. We use the new putative interactors to gain further insight on the regulatory roles that hPer2 performs, in conjunction with operating as a core factor in circadian rhythmicity. We also show that Translationally Controlled Tumor Protein (TCTP) is capable of binding to hPer2 and is a novel interaction. When a sufficient amount of TCTP (1:1 molar stoichiometric ratio) is present in a system, a cleavage of hPer2 is observed in vitro. This cleavage occurs in reactions independent of ATP, ubiquitin, and the proteasome. The data points towards a method of cleavage similar to that of the archael lon-tk (Thermococcus kodakaraensis) that preferentially cleaved unstructured substrates in ATP-independent reactions.
Master of Science

Le cancer de la prostate (CaP) représente la deuxième cause de mortalité par cancer chez l'homme. La suppression androgénique (castration-thérapie) demeure la seule thérapie efficace du CaP avancé du fait de son caractère castration-sensible. Cependant, elle n'empêche pas la progression castration-résistante (CR) de la maladie dans les 1 à 3 ans après le début du traitement hormonal. Récemment, l'implication d'Hsp27 (Heat shock protein 27) dans l'échappement thérapeutique des CaPs a été montrée et un oligonucléotide antisens inhibiteur d'Hsp27, OGX-427, est en cours d'évaluation clinique II/III pour le traitement des CaPs CR. Afin de comprendre le rôle d'Hsp27 dans le mécanisme de résistance à la castration, nous avons réalisé le criblage de l'ensemble des protéines partenaires d'Hsp27 par double hybride. Mes travaux de thèse ont permis d'identifier une nouvelle protéine cliente d'Hsp27, TCTP (translationally controlled tumor protein) dont l'expression est indétectable dans les cellules normales. J'ai également montré que la progression CR des CaPs corrélait avec une surexpression de TCTP, une perte de P53 et que l'inhibition de TCTP par un oligonucléotide antisens restaurait l'expression de P53. Cette étude suggère, pour la première fois, un lien direct entre P53 et la sensibilité à la castration des CaPs. De plus, l'étude de l'interactome d'Hsp27 a mis en évidence son implication dans de nouvelles fonctions telles que la réparation de l'ADN ou l'épissage alternatif des ARNm. L'ensemble de ces travaux ont permis de mieux comprendre les mécanismes d'action d'Hsp27 dans la progression CR des CaPs et de développer de nouvelles approches thérapeutiques
Prostate cancer (PC) is the second most common cause of cancer-related mortality in men in the Western world. Androgen ablation (castration-therapy) is usually the initial therapy in patients with advanced or metastatic disease. Unfortunately, the disease gradually progresses to a metastatic castration-resistant (CR) state, which remains incurable. Recently, the involvement of Hsp27 (Heat Shock Protein 27) in CR progression has been identified and an oligonucleotide antisense (OGX-427), inhibitor of Hsp27 is currently in phase II/III clinical trials to treat CRPC. In order to understand Hsp27 mechanisms of action in CR progression, we started to screen for Hsp27 partner proteins by using two-hybrid system. My PhD work has reported that Translationally Controlled Tumor Protein (TCTP) was a new Hsp27 protein partner that mediated Hsp27 cytoprotection in CRPC and that TCTP expression was absent in normal prostate tissues. We have further found that CR progression correlated with TCTP overexpression, the loss of P53 and that TCTP silencing using an antisense was able to restore P53 expression and function. This study suggests for the first time that castration-sensitivity is directly linked to P53 expression. In addition, we revealed exciting new aspects of the Hsp27 involvement in essential metabolic and cellular processes such as DNA repair and mRNA splicing. In summary, my PhD results have provided an enriched understanding of Hsp27 mechanisms of cytoprotection contributing to CRPC progression and opened a new promising field of research for multi-target therapeutic approaches

L'objectif de mon travail de doctorat était une caractérisation fonctionnelle des gènes TCTP et TSAP6. Ces gènes sont impliqués dans la réversion tumorale et forment un complexe protéique.
Tpt1, codant pour la protéine TCTP, est le gène le plus sous-exprimé lors de la réversion tumorale. L'analyse du cristal de TCTP humain montre une forte homologie entre ses hélices H2-H3 et les hélices H5-H6 de Bax. Grâce à ses hélices, TCTP inhibe l'apoptose induite par Bax au niveau des mitochondries. En effet, nous démontrons que TCTP, entre autres par le biais de ces hélices, empêche la dimérisation de Bax.
Nous avons aussi développé une lignée de souris TCTP knockout qui présentent une létalité embryonnaire précoce.
En parallèle, nous avons étudié TSAP6, qui encode pour une protéine à 6 domaines transmembranaires et qui est une cible transcriptionnelle directe de la p53. Nous avons établi une lignée murine TSAP6 knockout présentant une anémie microcytaire avec une splénomégalie. Les réticulocytes issus des souris knockout présentent un retard de maturation et une anomalie de sécrétion du Récepteur à la Transferrine par les exosomes. De manière plus générale, les résultats obtenus montrent, in vivo, que TSAP6 contrôle la sécrétion des exosomes induite par activation de la P53. Nous montrons aussi que la Sertraline et la Thioridazine empêchent la formation du complexe TSAP6-TCTP.

La réversion tumorale est un événement naturel qui conduit les cellules cancéreuses à retrouver spontanément un phénotype tumoral significativement atténué. Ce processus de reprogrammation cellulaire survient très rarement (au rythme d’une cellule par million), et suggère que des composés (petites molécules chimiques) seraient susceptibles de stimuler la réversion tumorale dans le but de constituer une nouvelle classe de médicaments novateurs pour soigner des patients atteints du cancer. Pour ce faire, la protéine TCTP (« Translationally Controlled Tumor Protein ») a été identifiée comme étant une cible moléculaire majeure dans la réversion tumorale. Par conséquent, identifier des composés capables de stimuler cette réversion, par inhibition de la protéine TCTP, constitue une nouvelle stratégie prometteuse dans le traitement des cancers.Dans ce contexte, ce projet de thèse vise à concevoir et synthétiser de nouveaux inhibiteurs de la protéine TCTP, des analogues de la sertraline, un médicament actuellement sur le marché en tant qu’antidépresseur, mais ayant montré une efficacité significative dans le phénomène de réversion tumorale. Dans un second temps, ces analogues seront testés lors de contrôles variés (affinité, cytotoxicité, processus ADMET, etc.) afin de déterminer un "pré-lead" qui sera finalement évalué in vivo. De plus, ces travaux de recherches sont aussi axés sur les optimisations des méthodes initialement utilisées, ainsi que le développement de nouvelles voies de synthèse innovantes pour la formation des inhibiteurs de la protéine TCTP
Tumor reversion is a natural process that was discovered for the first time in the early 1960s. It is a biological phenomenon by which highly tumorigenic cells lose at great extent or entirely their malignant phenotype. This is a rare molecular program (one cell for a million cancer cells) which suggests that organic compounds could stimulate this process and form a new class of medicinal products susceptible to treat cancer patients. For those purposes, the translationally controlled tumor protein (TCTP) has been identified as a major therapeutic target of tumor reversion. Consequently, identification of products that are capable of stimulating this phenomenon, by TCTP inhibition, will constitute a promising new strategy for the treatment of the disease.In this context, the goal of this thesis is to design and synthesis new TCTP inhibitors, analogues of sertraline. This latter is a widely used antidepressive drug but it also shows significant efficacy throughout the tumor reversion program. In the second part, those analogues will undergo diverse biological essays (affinity, cytotoxicity, ADMET process…) in the aim of identifying a potential lead compound which will be evaluate under in vivo conditions. Moreover, this research is also focus on the optimizations of the first synthetic route and the development of innovative methods to access to those new TCTP inhibitors

Pulmonary arterial hypertension (PAH) is a lethal disease characterized by excessive proliferation of pulmonary vascular cells, such as endothelial cells (ECs). Hereditary (H) PAH is mainly caused by ―loss-of-function‖ mutations in the gene coding for the bone morphogenetic protein type II receptor (BMPR2). However, the mechanisms by which these mutations cause PAH remain unclear. The hypothesis of this thesis was that BMPR2 mutations produce an imbalance in EC protein expression and/or activity that is integrally related to the development of abnormalities in lung vascular function and structure in HPAH. Patient-specific blood-outgrowth endothelial cells (BOECs) expanded ex vivo from peripheral blood mononuclear cells from patients with HPAH and healthy subjects were used to examine the consequences of BMPR2 mutations on the BOEC protein expression profile as well as on their functionality. Functional analyses of the BOECs revealed that HPAH-derived BOECs are more susceptible to apoptosis and more proliferative compared with healthy controls. Protein isolates of BOECs from patients with HPAH and from healthy subjects were subjected to 2-D gel electrophoresis and stained for total proteins and phosphoproteins, and to a quantitative computerassisted analysis. Differentially regulated proteins were identified by mass spectrometry (LC-MS/MS). Of the 416 total proteins detected under basal conditions, 11 were significantly downregulated in HPAH-derived BOECs and 11, including the translationally controlled tumor protein (TCTP), were upregulated. TCTP has previously been shown to be involved in systemic arteriolar remodeling, inflammation and growth. Therefore, the potential role of TCTP in PAH was studied in vivo in the SU5416 rat model of severe angioproliferative PAH. Immunofluorescence staining revealed high expression of TCTP in arteriolar ECs of PAH lungs tightly localized to proliferating cells within occlusive intimal lesions; whereas, only minimal TCTP expression was seen in vascular ECs of normal lungs. Similarly, abundant TCTP immunostaining was also seen in human PAH lung sections, again associated with complex vascular lesions. In BOECs, TCTP was found to participate in cell growth and survival. These data suggest that TCTP could play an important role in PAH by mediating pro-survival and growth signaling in vascular cells, contributing to occlusive pulmonary vascular remodeling triggered by EC apoptosis.

Dans les organismes pluricellulaires la morphogenèse nécessite une étroite régulation de la prolifération, de la croissance et de la mort cellulaire, permettant la formation d’organes aux formes et tailles bien spécifiques. Au cours de ma thèse, je me suis intéressé aux rôles biologiques de deux gènes impliqués dans la morphogenèse des organes chez Arabidopsis thaliana, TRANSLATIONALLY CONTROLLED TUMOR PROTEIN (AtTCTP) et BIGPETALp (BPEp). J’ai montré que AtTCTP est essentiel pour le développement des plantes et que AtTCTP contrôle la progression du cycle cellulaire, au niveau de la transition G1/S. En outre j’ai montré que cette fonction a été conservée au cours de l’évolution entre les plantes et les animaux. BPEp encode un facteur de transcription de type bHLH, qui régule l’élongation cellulaire dans les pétales. J’ai montré que l’accumulation du transcrit de BPEp est positivement contrôlée par le jasmonate, une phytohormone, et que cette régulation a lieu de manière post-transcriptionnelle. J’ai par ailleurs démontré que le jasmonate contrôle l’expansion cellulaire au sein du pétale. Nous avons également identifié le facteur de transcription AUXIN RESPONSE FACTOR 8 (ARF8) comme interacteur putatif de BPEp. Des études d’interaction génétique et biochimique avec ARF8 ont montré que BPEp s’inscrit dans un réseau régulé par une autre phytohormone, l’auxine. En résumé mes résultats contribuent à mieux comprendre l’organogenèse au sein des plantes, grâce à la caractérisation fonctionnelle de la protéine clé conservée TCTP, qui contrôle la croissance mitotique, et du facteur de transcription phytohormono dépendant BPEp, qui régule la croissance post mitotique
In multicellular organisms, morphogenesis requires the tight regulation of cell proliferation, growth and death, in order to form organs with specific shapes and sizes. During my Ph. D. Thesis work, I addressed the biological roles of two genes involved in organ morphogenesis in the plant model species Arabidopsis thaliana, namely TRANSLATIONALLY CONTROLLED TUMOR PROTEIN (AtTCTP) and BIGPETALp (BPEp). I showed that AtTCTP is essential for plant development and that AtTCTP controls the cell cycle progression, particularly at the G1/S transition. Furthermore I showed that this function of AtTCTP in regulating cell proliferation is evolutionarily conserved between plants and animals. BPEp encodes a bHLH transcription factor that regulates cell elongation in developing petals. I showed that the accumulation of BPEp transcript is positively controlled by a signal initiated by the phytohormone jasmonate and that this regulation occurs at the post-transcriptional level. I also demonstrated a role of jasmonate in the control of cell expansion during petal growth. Search for BPEp putative binding proteins identified an AUXIN RESPONSE FACTOR (ARF8) as putative interactor of BPEp. Studies of molecular and genetic interaction with ARF8 demonstrated that BPEp is inscribed in a network regulated by auxin, a second phytohormone. In summary my results together help to better understand how plants regulate organogenesis, thanks to the functional characterization of the conserved key player TCTP, which is involved in the control of mitotic growth, and of the phytohormone-dependent transcription factor BPEp, which regulates post-mitotic growth

Made available in DSpace on 2015-03-26T13:51:57Z (GMT). No. of bitstreams: 1 texto completo .pdf: 1092167 bytes, checksum: 8586b9a4bcc728e0319bbbdb012ca136 (MD5) Previous issue date: 2012-07-19
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Viruses are organisms with small genomes of simple organization, which coding about 3 to encode 10 viral proteins. The success of the infection depends on the manipulation of the cell by the virus, by means of complex interactions occurring between viral factors and host factors. The induced changes by virus infection include cell morphology changes, cell cycle changes and alterations in gene expression, among others. Understanding the processes that favor viral infection necessarily involves the study of virus-host interactions. In order to better understand the processes related to infection by tomato potyvirus Pepper yellow mosaic virus (PepYMV) a subtractive library was built 72 hours after infection. Several genes were identified as induced or repressed by viral infection. Among the induced genes, is the gene encoding the Translationally controlled tumor protein (TCTP). TCTP protein is highly conserved in all eukaryotes. Its functions are related to growth control and cell cycle, anti-apoptotic activity, and response to different biotic and abiotic stresses. The involvement of this protein in infection PepYMV has not been established, but studies in a strain of transgenic tomato plants silenced for TCTP showed that the silenced plants have a lower accumulation of PepYMV, indicating that TCTP promotes viral infection. In this study, we sought to advance the understanding of mechanisms involving TCTP in the process of infection by PepYMV. N. benthamiana plants silenced by VIGS TCTP were used to study the effect of silencing in viral infection, and the silenced plants accumulate fewer viruses in early stages of virus infection. Individual expression of viral proteins in N. benthamiana identified P3 and CP as capable of inducing TCTP expression at similar levels to those induced during PepYMV infection, and expression of NIb reduced expression of TCTP. The verification of direct interactions occurrence between viral proteins and TCTP by double-hybrid assay showed that TCTP not interact separately with any of the proteins of viral origin. Purification of proteins of health and infected N. benthamiana plants by affinity with TCTP identified several proteins that putativaly interacts with TCTP. As in two hybrid assay, interactions involving PepYMV proteins were not detected. These results sugests that TCTP actuation must involve the formation of protein complexes involving viral and plant proteins or contribute indirectly to PepYMV infection, without involving direct interactions between TCTP and viral proteins.
Os vírus são organismos com genomas pequenos, de organização simples, que codificam em média 3 a 10 proteínas. O sucesso da infecção depende da manipulação da célula pelo vírus, por meio de interações complexas que ocorrem entre fatores virais e fatores do hospedeiro. As modificações induzidas na célula incluem alterações morfológicas, alteração do ciclo celular e na expressão gênica, entre outras. A compreensão dos processos que favorecem a infecção viral passa necessariamente pelo estudo de interações vírus-hospedeiro. No intuito de compreender melhor os processos relacionados à infecção de tomateiros pelo potyvírus Pepper yellow mosaic virus (PepYMV) uma biblioteca subtrativa foi construída 72 horas após a infecção. Diversos genes cuja expressão foi alterada pela infecção foram identificados. Dentre os genes induzidos, se encontra o gene que codifica a Translationally controlled tumor protein (TCTP). A proteína TCTP é altamente conservada em todos os eucariotos. Suas funções estão relacionadas a controle do crescimento e ciclo celular, atividade anti-apoptótica, e resposta a diferentes tipos de estresses abióticos e bióticos. O envolvimento desta proteína na infecção pelo PepYMV ainda não foi estabelecido, porém estudos em uma linhagem de tomateiro transgênica silenciadas para a TCTP, mostraram que as plantas silenciadas apresentam um menor acúmulo de PepYMV, indicando que a TCTP favorece a infecção por este vírus. Neste trabalho, buscou-se avançar na compreensão dos mecanismos que envolvem a TCTP no processo de infecção pelo PepYMV. Plantas de Nicotiana benthamiana silenciadas para TCTP por VIGS (Virus Induced Gene Silence) foram utilizadas para estudar o efeito do silenciamento na infecção viral, sendo que as plantas silenciadas acumularam menos vírus no início da infecção. A expressão individual das proteínas de origem viral em N. benthamiana identificou a P3 e a CP como capazes de induzir a expressão de TCTP em níveis semelhantes aos observados durante a infecção pelo PepYMV, sendo que a expressão da proteína NIb reduziu a expressão de TCTP. A verificação da ocorrência de interações diretas entre a TCTP e as proteínas virais, por ensaio de duplo híbrido, mostrou que a TCTP não interage separadamente com as proteínas de origem viral. A purificação de proteínas de plantas de N. benthamiana, sadias e infectadas, por afinidade com a TCTP identificou diversas proteínas que possivelmente 7 interagem com a TCTP. Assim como no ensaio de duplo híbrido, a interação com proteínas virais não foi detectada. Estes resultados sugerem que o papel da TCTP deve envolver a formação de complexos proteicos entre proteínas virais e da planta, ou favorecer a infecção de forma indireta.

La croissance d’un organisme multicellulaire pour atteindre une taille bien définie, nécessite une coordination de la prolifération cellulaire, de l’expansion et de la différentiation cellulaire ainsi que de la mort cellulaire. Ces processus sont sous l’influence de l’état nutritionnel de l’organisme, les conditions de son environnement et des signaux hormonaux. Translationally controlled tumor protein (TCTP) est un facteur essentiel à la croissance des plantes et des animaux. La protéine TCTP de plante contrôle la croissance mitotique, tandis que la protéine TCTP animale contrôle la croissance mitotique et post-mitotique. Une voie importante dans la régulation de la croissance en réponse aux nutriments est la voie Target of Rapamycin (TOR). Chez la Drosophile, il a été montré que dTCTP serait un régulateur positif en amont de TOR. Au cours de ma thèse, j’ai étudié le lien entre TCTP et la voie TOR, afin de savoir si, comme chez les animaux, AtTCTP agit en amont de la voie TOR pour contrôler la croissance des organes. Afin de savoir si la voie TCTP était liée à l’état nutritionnel, j’ai recherché l’impact du milieu de culture sur la létalité de la mutation tctp. J’ai ensuite caractérisé l’impact de la mutation tctp sur le transport et l’homéostasie de l’hormone auxine. J’ai enfin analysé pourquoi TCTP de plante ne contrôle pas la croissance post-mitotique par expansion cellulaire, contrairement à TCTP animale. Les données de la littérature montrent que chez les animaux TCTP est un activateur positif en amont de la voie TOR. Chez la plante Arabidopsis thaliana, mes données d’interactions génétiques sont en faveur d’un modèle dans lequel AtTCTP agit indépendamment de la voie TOR, contrairement de ce qu’il a été proposé chez les animaux. Chez les plantes, la perte de fonction de TCTP est associée à un retard du développement embryonnaire et à la mort. Cette létalité peut être complémentée par sauvetage des embryons sur du milieu riche en nutriments. J’ai montré que l’ajout de sucrose ou de glutamine dans le milieu de sauvetage des embryons tctp est nécessaire à leur développement. Ces données suggèrent qu’in vitro, AtTCTP n’est pas nécessaire à l’approvisionnement et à l’utilisation des nutriments sucrose, glucose ou glutamine. Dans leur ensemble, ces résultats réévaluent le rôle du régulateur de croissance TCTP en montrant que le gène AtTCTP régule la croissance mitotique indépendamment de la voie TOR et des voies de signalisation liées aux nutriments. L’observation des flux d’auxine en suivant la localisation de PIN1-GFP dans les embryons et les inflorescences du mutant tctp ne montre aucune altération par rapport au phénotype sauvage. De même, l’homeostasie de l’auxine, suivie à l’aide du rapporteur DR5::GFP n’est pas altérée dans les embryons tctp. Ceci suggère que le défaut de croissance du mutant tctp n’est pas lié à une altération du flux ou de l’homéostasie de l’auxine. La protéine TCTP de plante ne contrôle pas la croissance post-mitotique, contrairement à la protéine TCTP animale. J’ai réalisé un échange de domaines protéiques entre AtTCTP et Drosophila dTCTP. Le but était d’identifier les domaines protéiques de la protéine TCTP animale qui permettent la croissance post-mitotique. La plupart des protéines chimères étaient instables dans la Drosophile. Afin de comprendre pourquoi, j’ai réalisé du modelage par homologie et j’ai discuté la structure des chimères dans ma thèse.L’ensemble de mes résultats permet de mieux comprendre la fonction de TCTP chez les végétaux, en montrant que cette fonction s’exerce indépendamment de la voie TOR
The growth of a multicellular organism and its size determination require the tight regulation of cell proliferation, cell differentiation, cell growth and apoptosis. These processes are influenced by the nutritional state of the organism, its environmental conditions and hormonal signals. Translationally controlled tumor protein (TCTP) is an essential regulator of growth in plants and animals. In plants it controls mitotic growth, whereas in animals, it controls mitotic and post-mitotic growth. One of the important pathways involved in the control of growth in response to nutrients is the Target of Rapamycin (TOR) pathway. In Drosophila, dTCTP was proposed to act a positive regulator upstream of TOR, although this role remains a matter of debate in the animal field.During the past 3 years of my PhD. thesis, I addressed the question whether plant TCTP acts upstream of TOR to control organ growth. I studied the impact of nutrient availability and hormones on TCTP role to control growth in plants and vice versa. Finally, I examined why plant TCTP does not control post-mitotic cell expansion growth, conversely to animal TCTP using a structure-function approach.In animals, TCTP was proposed to act as a positive activator upstream of the TOR pathway. In plants, my data support a model in which AtTCTP acts independently from the plant TOR pathway, thus in contrast to what has been proposed in animals. TCTP loss of function leads to delay of embryo development and death. Nutrient supplement rescues this embryos lethality. First, I demonstrate that embryos grown on nutrients lacking sucrose or glutamine fail to develop correctly. My data demonstrate that in vitro AtTCTP is not essential to the uptake, the use of and the response to the nutrients glucose, sucrose or glutamine. Taken together, these results reevaluate the role of AtTCTP as a growth regulator controlling mitotic growth independently from the TOR pathway and likely from nutrient related signaling pathways. Interestingly, my data also show that AtTCTP controls growth independently from auxin flux or homeostasis and that auxin-induced growth can occur without TCTP. To address why plant TCTP do not control post-mitotic growth conversely to animal counterpart, I performed protein domain swaps and created chimera proteins between Arabidopsis AtTCTP and Drosophila dTCTP. The rational was to identify protein domains that differentiate plant and animal TCTPs with regard to post-mitotic growth control. Most of chimera proteins were instable and I was unable to complement tctp loss of function in Drosophila. I performed a structure based modeling to understand this phenotype and the outcome is discussed in my PhD thesis.Altogether my results improve the understanding of plant morphogenesis by reevaluating the role of the central growth regulator TCTP

TCTP (Translationally Controlled Tumor Protein) est une protéine très conservée chez l'ensemble des eucaryotes. C’est une protéine vitale impliquée dans divers processus essentiels, et pour de nombreux organismes son absence conduit à la létalité dès les stades embryonnaires.Chez les animaux comme chez les végétaux, TCTP joue un rôle primordial dans la croissance et le développement des individus. En plus de son implication dans l’apoptose et la réparation de l’ADN, TCTP favorise la prolifération cellulaire, et se trouve donc être un élément important de la tumorigenèse. Chez les végétaux, la forte conservation de TCTP a permis la préservation de la plupart des fonctions décrites chez les animaux, mais les facteurs qui interviennent en amont ne sont pas encore connus.Par la mise en place, la conduite et la finalisation de deux cribles génétiques utilisant la plante modèle Arabidopsis thaliana, ce travail de thèse a cherché à identifier des facteurs situés en amont de TCTP. En parallèle, une seconde étude fut menée afin de mesurer l'impact de l'absence de TCTP sur les voies de l’auxine et des cytokinines au cours du développement embryonnaire, permettant de mieux comprendre l’origine de l’embryolétalité du mutant tctp
TCTP (Translationally Controlled Tumor Protein) is strongly conserved among eukaryotes. It is a vital protein implicated in various major processes, and its absence leads to early embryolethality in many organisms. In plants as in animals, TCTP is a key factor of growth and development. Implicated in apoptosis and DNA repair, TCTP is also an enhancer of cell proliferation, and is a key element of tumorigenesis. Major functions of TCTP are conserved between plants and animals, but upstream factors are not known yet. Using a genetic screen on the model plant Arabidopsis thaliana, the principal goal of this thesis was to discover regulators of TCTP.In parallel, the impact of TCTP knockout on auxin and cytokinin pathways during embryo development was investigated

Background: Pulmonary arterial hypertension (PAH) is a lethal disease for which the fundamental molecular mechanisms are only partially understood. Existing therapies, which primarily focus on endothelial dysfunction, have limited effects on improving outcomes. Increases in pulmonary vascular resistance in PAH may be attributed to complex lung arterial remodeling which result in obliterative “plexiform” lesions, a pathological hallmark of this disease. Recent studies have shown that endothelial cell (ECs) apoptosis may be a central trigger for PAH, resulting in the emergence of growth-dysregulated and apoptosis-resistant ECs that contribute to the formation of complex neoplastic-like vascular lesions. However, the mechanism which links ECs apoptosis to dysregulated growth is not yet known. Previous studies in our lab have identified increased expression of translationally controlled tumor protein (TCTP) and its gene (TPT1), previously implicated in the transformation of neoplastic cells in cancer, and in blood outgrowth ECs from patients with PAH. Moreover, TCTP expression was found to be elevated in the lungs of patients with PAH, and tightly localized to complex arterial lesions. In addition, it was detected in obliterative intimal lesions of an experimental rat model of severe PAH. Hypothesis: TCTP represents a central molecular mechanism linking ECs apoptosis to the emergence of growth-dysregulated lung vascular cells and occlusive, complex arterial remodelling in PAH. Specific Hypotheses: - Lentiviral overexpression of TCTP in human umbilical vein endothelial cells (HUVECs) and pulmonary artery smooth muscle cells (PASMCs) leads to a hyperproliferative and apoptosis-resistant phenotype. - Overexpression of TCTP will increase its export into apoptotic extracellular vesicles, thereby augmenting cell-cell signalling between ECs and neighbouring SMCs. Purpose: My objective was to examine the effects TCTP overexpression on ECs and SMCs survival in terms of proliferation and apoptosis, and TCTP release on the survival of nontransduced ECs and SMCs. Methods and Results: The effect of TCTP overexpression on ECs growth and survival was studied using in vitro models. TCTP was overexpressed via a lentivirus vector in HUVECs and PASMCs. Compared to non-transfected or null transfected cells, TCTP overexpression led to increases in BrdU incorporation, consistent with hyper-proliferation, and decreases in caspase activity, consistent with apoptosis resistance. As well, TCTP was selectively exported into the conditioned media of apoptotic ECs, but not SMCs, despite similar levels of overexpression. In addition, the level of release was greater in serum starved conditioned media in comparison to the exosome fraction. Finally, our data demonstrates a selective effect of conditioned media (CM) from serum-starved ECs on PASMCs, but not ECs, in terms of an increase in proliferation and a decrease in apoptosis. Conclusions: These support the idea that TCTP overexpression confers an increase in the survival of SMCs and HUVECs. Moreover, TCTP released from apoptotic ECs leads to a growth-dysregulated phenotype within SMCs (but not ECs) and may contribute to the formation of complex lung arterial lesions, leading to arteriolar obliteration in PAH. Finally, an increase in the level of TCTP expression via lentiviral transduction led to an increased TCTP export into the media, but this appeared to be mostly in the soluble portion, and less was associated with exosomes.

Das translationell kotrollierte Tumorprotein (TCTP) ist ein bei Eukaryonten vorkommendes hochkonserviertes Protein, das eine Rolle bei der Pathogenese allergischer Erkrankungen spielt. Bei atopischen Kindern vermittelt es eine IgE abhängige Histaminfreisetzung aus basophilen Granulozyten. Die zugrundeliegenden Mechanismen sind jedoch unklar. TCTP hat die Eigenschaft, an das Tubulin des Zytoskeletts der Zelle zu binden und besitzt eine hohe Affinität für Kalzium. Seine Synthese wird auf dem transkriptionellen und translationellen Niveau reguliert. Eine früher angenommene spezifische Funktion in Tumorzellen konnte nicht bestätigt werden. Das für TCTP kodierende Gen wird als TPT1 bezeichnet. Um die molekulare Basis für die Kontrolle der Synthese des TCTP zu verstehen, wurden in dieser Arbeit Struktur und Funktion des TPT1-Gens bei Mensch und Kaninchen untersucht. Erstmalig wurde die vollständige Struktur eines Säuger-TPT1-Gens durch Klonierung und Sequenzierung aufgeklärt und die funktionelle Rolle des Promotors analysiert. Das 3,8 kb große Kaninchengen wird durch fünf Introns unterbrochen, und kodiert für zwei mRNAs von 843 und 1163 nt, die sich in der Länge der 3' untranslatierten Region unterscheiden. Sie entstehen durch alternative Polyadenylierung. Vom Human-Gen wurden genomische Rekombinanten isoliert und seine vorläufige Struktur ermittelt. Es besitzt eine identische Intron/Exon Architektur und unterscheidet sich nur geringfügig in der Länge der Introns. Auch bei der Expression des Human-Gens entstehen zwei mRNAs. Hybridisierungsexperimente mit RNA aus 10 Kaninchen- und 50 Human-Geweben zeigten, daß beide TCTP mRNAs in allen untersuchten Geweben in ähnlichem Verhältnis zueinander exprimiert werden. Die Gesamtkonzentrationen der TCTP- mRNAs unterschied sich jedoch in verschiedenen Gewebegruppen bis zum Faktor 100. Dies deutet auf eine ausgeprägte Regulation der gewebsspezifischen Transkription hin. Die Promotorstrukturen von 1,2 kb 5'-flankierender Sequenzen des Kaninchen- Gens wurden mit Computerprogrammen auf Bindungsstellen für Transkriptionsfaktoren analysiert. Für funktionelle Aussagen wurden Promotorfragmente mit dem Chloramphenicol-Acetyltransferase-Gen (cat) gekoppelt und die Promotoraktivität durch Bestimmung der CAT-Enzymaktivität nach Zelltransfektionen ermittelt. Ein minimaler Promotor von 66 bp Länge, der eine TATA-Box enthält, konnte eingegrenzt werden. Die maximale Promotoraktivität, die 90% im Vergleich zum starken Thymidinkinase-Promotor betrug, war mit einem 290 bp langem Fragment assoziiert und enthielt eine SP-1, zwei AP-1/CREB und zwei ETS Bindungsstellen. Diese Konstellation ist ein häufiges Merkmal von Genen, die wie das TPT1-Gen durch Phorbolester und Lipopolysaccharide induzierbar sind. Im Sequenzbereich bis -160 sind die Promotoren des Human- und des Kaninchen-Gens sehr ähnlich (89% Homologie), alle Bindungsorte für Transkriptionsfaktoren sind hier konserviert. Weiterhin wurde im Kaninchengenom eine Vielzahl von prozessierten TPT1- Pseudogenen.gefunden. Sechs von ihnen und ihre genomisch-flankierenden Integrationsorte wurden sequenziert. Sie repräsentierten beide mRNA Typen und waren zu über 99% zu den korrespondierenden mRNAs homolog. Die Leserahmen aller Pseudogene waren intakt, bei zwei Pseudogenen war die Aminosäuresequenz sogar unverändert erhalten. Die durch CAT-Assays getestete Transkriptionsaktivität der 5'flankierenden Region eines Pseudogens zeigte eine Aktivität von über 15% gegenüber dem authentischen TPT1-Promotor. Dies ist ein Indiz für eine mögliche Expression von TPT1 Pseudogenen in vivo.
The translationally controlled tumor protein (TCTP) is a conserved eukaryotic protein, which is involved in the pathogenesis of allergic diseases. In atopic children it has been reported to mediate histamine release from basophilic leukocytes in an IgE dependent way. The underlying mechanism, however, is unknown. TCTP is characterized by an efficient binding to tubulin of cytoskeletal structures and by a high calcium affinity. Its synthesis is regulated at the transcriptional and translational level. A specific function in tumor cells, which was assumed initially, could not be confirmed. The gene coding for TCTP is called TPT1. To understand the molecular basis for the control of TCTP expression structure and function of the human and rabbit TPT1 genes were investigated including their promoter regions. The first mammalian TPT1 gene (rabbit) was cloned and sequenced. It consists of 3.8 kb and is interrupted by five introns. Two mRNAs of 843 and 1163 nt length are transcribed differing in their 3'untranslated regions. They are generated by alternative polyadenylation. Furthermore genomic recombinants were isolated containing the human TPT1 gene and a preliminary structure of the gene was established. The human gene has the same intron/exon architecture as the rabbit gene just differing in the length of its introns. Human multi-tissue dotblots revealed an identical transcription pattern for both mRNAs. The concentration of the TCTP mRNAs differed up to the factor 100 between different tissues, indicating distinct tissue specificity in transcriptional control. 1.2 kb 5'flanking promoter structures were analyzed for transcription factor binding sites. For functional studies TPT1 promoter fragments were fused to the chloramphenicol acetyltransferase (CAT) reportergene and assayed by cell transfection and CAT enzyme activity. A basic promoter of 66 bp length containing a TATA box could be defined. Maximal promoter activity of 90% compared to the strong thymidine kinase promoter was associated with a fragment of 290 bp containing a SP-1, two AP-1/CREB and two ETS binding sites. This is a common feature of genes like TPT1, which are inducible by phorbolesters and lipopolysaccharides. Furthermore, numerous processed TPT1 pseudogenes were found spread through the rabbit genome. Six pseudogenes and their flanking genomic integration sites were sequenced. They represented both mRNA types and were at least 99% homologous to the corresponding mRNAs. In all pseudogenes the open reading frames were retained and in two of them the original amino acid sequence was even conserved completely. The 5'flanking region of one pseudogene was tested for transcriptional activity by CAT assays and revealed an activity of about 15% of the authentical TPT1 promoter. This could suggest a possible expression of TPT1 pseudogenes in vivo.

Being sessile, plants need to accurately coordinate leaf and root growth to adapt to changing environmental conditions. TCTP (Translationally Controlled Tumour Protein) belongs to a conserved gene family, present in all eukaryotes. In animals, TCTP controls several core cellular processes including apoptosis, cellular proliferation and growth, tissue patterning, and is thought to interact with the TOR (Target Of Rapamycin) pathway. Plant TCTPs are little known, however, but recent studies suggest functional similarities with animal TCTPs. What functions they assume is still a matter of debate and how they promote organ and whole organism growth is controversial, although they are widely described as mitotic activators, but with no role in cellular growth. In addition, plant TCTPs have never been shown to have extracellular functions and act as signalling molecules as known of animal TCTPs. This Thesis investigates TCTP function in plant development. Using Arabidopsis as a model plant species, and focusing on AtTCTP1, I probe the role of AtTCTP1 in the expansive growth of non-proliferative cells; I explore the AtTCTP1 molecular pathway in the control of root elongation and embryogenesis; and I investigate the physiological relevance to root development of AtTCTP1 mRNA and protein mobility. To fulfil these aims I carried out a kinematics analysis of primary root and hypocotyl development. This included the development of a custom imaging and bioinformatic pipeline for in situ, high throughput acquisition of spatial profiles of cell sizes and expansion rates. The results demonstrate that AtTCTP1 acts in the positioning of frontiers between proliferating, expanding only, and maturing cells in roots; controls cell size at division, hence the balance between expansion and partitioning rates in meristematic cells; and promotes the growth and final size of non-proliferative cells, in the root elongation zone and also the hypocotyl, indicating this is a likely a general function. Supporting this, TCTP1 also promotes tip growth in root hairs. Taken together, these results demonstrate that, similar to animal TCTP, plant TCTP is a pivotal cell and organ growth controller. Combining genetic, microscopy and pharmacological approaches I next demonstrate that TCTP1 constitutes an upstream component of the core TOR pathway, and is crucial to its activation. Moreover, I establish the function in root development of a small GTPase as an effector of TCTP-mediated activation of the TOR pathway. To investigate the possibility that plant TCTPs may also have a signalling role in root development, I used a micrografting technique to generate heterografts between Arabidopsis TCTP1 transgenic and wild type seedlings, including seedlings expressing a TCTP1::GFP fusion protein. I monitored rootstock elongation and branching in relation to the patterns of GFP signal and the respective genotypes of root-stock and scion. These experiments demonstrated the existence of bi-directional movement of AtTCTP1 mRNA between scion and rootstock, and an active, destination-controlled accumulation of shoot-derived TCTP1 protein at sites of lateral root initiation. Long-distance mobility of shoot TCTP1 mRNA promotes lateral root initiation and emergence, and appears as one of the elusive controllers of the spatial patterning of lateral roots along the primary root. Remarkably, TCTP1 rootward mobility modulated root system architecture without impacting the overall length of root produced. This points to a role of AtTCTP1 gene products in the regulation of the trade-off for a root between branching or elongating more, to greater depth. These findings provide the first evidence of an extracellular function of TCTPs in plants. Altogether, this work introduces a new paradigm for the physiological roles of plant TCTPs, positioning them as agents of systemic signalling between leaves and roots, and essential coordinators of cell proliferation and growth, upstream of TOR.

Sphingosine kinase 1 (SK1) is responsible for phosphorylating the lipid sphingosine, generating the bio-active phospholipid, sphingosine 1-phosphate (S1P). Cells possess basal SK1 activity which has been proposed to serve in a ‘housekeeping’ function to limit the levels of proapoptotic sphingosine and ceramide in the cell. In some circumstances, however, such as cell exposure to growth factors and cytokines this basal level of SK1 activity is increased, resulting in an increased production of S1P. As S1P is a pro-proliferative, pro-survival molecule, its increased production is associated with enhanced cell proliferation, survival and an oncogenic phenotype. The Pitson laboratory has shown previously that one mechanism by which SK1 is activated is through phosphorylation at Ser-225 by ERK1/2. Here, my studies focused on alternative mechanisms of SK1 activation that arise through its interaction with two proteins, eukaryotic elongation factor 1A (eEF1A) and a relatively uncharacterised protein, SK activator molecule 1 (SKAM). eEF1A is able to directly increase the catalytic activity of SK1 in vitro and is also able to increase endogenous SK activity when over-expressed in quiescent cells that have reduced levels of endogenous eEF1A protein. Due to the abundance of eEF1A protein within a cell, I hypothesized that the effect of eEF1A on SK activity may be dynamically regulated. eEF1A contains a ‘G protein-like’ domain that enables it to bind GDP and GTP. When bound by GTP, eEF1A undergoes a large conformational change that enables it to bind aminoacyltRNA for transport to the ribosome. Similarly, just as the nucleotide-bound state of eEF1A regulates its role in protein synthesis, I found that the nucleotide-bound state of eEF1A also regulates its ability to activate SK1. Strikingly, it is only the translationally inactive eEF1A.GDP that can activate SK1. A truncated form of eEF1A named PTI-1 has been described that lacks the ‘G protein-like’ domain and thus can not bind guanine nucleotides, rendering it structurally analogous to eEF1A.GDP. In keeping with my finding that only eEF1A.GDP activates SK1, I found that PTI-1 also activates SK1 both in vitro and in cells. Importantly, PTI-1 has been previously characterized as an oncoprotein and for the first time my studies have shown a likely mechanism by which PTI-1 induces a tumourigenic phenotype. Expression of PTI-1 in NIH 3T3 cells induces neoplastic transformation, as measured by focus formation. Notably, this PTI-1-induced transformation is blocked when cells are treated with SK inhibitors or when cells are co-transfected with PTI-1 and a dominant negative SK1, indicating that oncogenesis by PTI-1 is mediated through SK1. The current study also investigated the regulation of SK1 activity by its interaction with SKAM1. Previous studies have shown that SKAM1, like eEF1A, can directly increase the catalytic activity of SK1 in vitro and in cells. My studies have determined the minimal region of interaction of SKAM1 that is still able to interact with and activate SK1. Remarkably, a 35 amino acid SKAM1 peptide retained the ability to activate SK1. The physiological relevance of the SK1-SKAM1 interaction was also examined and I have shown that knock-down of SKAM1, and the related protein SKAM2, in HEK 293T cells resulted in decreased cell proliferation coupled with increased susceptibility to apoptosis. Results presented here, also suggest that phosphorylation of SKAM1 at Tyr-46 acts as a negative regulator for SKAM1-induced SK1 activation. In summary, the current study presents two novel SK1 interacting proteins that directly increase the catalytic activity of this enzyme, and investigates mechanisms by which their effects on SK1 activity are regulated. While the guanine nucleotide bound state of eEF1A1 determines its effects on SK1 activity, the phosphorylation status of SKAM1 appears to determine its ability to activate SK1.
Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 2010

Tese de doutoramento em Biociências, ramo de especialização em Biologia Celular e Molecular, apresentada ao Departamento de Ciências da Vida da Faculdade de Ciências e Tecnologia da Universidade de Coimbra
With 86 billion neurons in the human brain, the ordered array of neuronal pathways is an exceptionally complex web of accurately connected axonal and dendritic processes, ultimately allowing us to perceive the world and respond consciously to it. Precise wiring of the nervous system is therefore the cornerstone of its intricate functions. Neuronal connectivity begins to take shape during embryonic development, when post-migratory newborn neurons send out a single threadlike axon that extends in a highly directed manner to the vicinity of its appropriate target region. Axon pathfinding relies on molecular ‘guideposts’ presented in the embryonic landscape and integrated by the growth cone, an amoeboid, sensory structure at the tip of developing axons first identified by the legendary Ramón y Cajal. Studies in the past three decades have revealed that a certain degree of functional autonomy is endowed upon this cellular outpost, perhaps best exemplified by the demonstration that axons separated from their cell bodies can still navigate correctly in vivo. It is now evident that this flexibility partly arises from the local regulation of the axonal proteome in response to extracellular cues. The local translation of new proteins elicited by these factors allows for rapid alterations in cytoskeleton dynamics, guidance receptor expression, substrate adhesion, as well as promoting axonal and mitochondrial maintenance. The recent appreciation of the complexity of the axonal transcriptome, with thousands of mRNAs identified, clearly illustrates the functional significance of this homeostatic mechanism. Here, I pioneered the study of translationally controlled tumor protein (Tctp) in the context of neural connectivity using the Xenopus laevis (African clawed frog) retinotectal projection as an in vivo model system. Tctp is an evolutionary conserved pro-survival protein implicated in cell growth and particularly well-studied in cancer pathogenesis, where its expression is often found upregulated and correlates with indicative markers of aggressive disease. Significantly, across diverse neuronal populations, including retinal ganglion cells, the tpt1 transcript, which encodes for Tctp, is ranked among the most enriched in the axonal compartment, suggestive of an unexplored relevant role in neurobiology. My most significant original contribution to knowledge is the identification of Tctp as a cell-autonomous checkpoint for axon development through its support of mitochondrial homeostasis. Specifically, Tctp deficiency during embryogenesis results in shorter retinotectal projections that fail to reach their target at the appropriate developmental window. Tctp-depleted axons exhibit mitochondrial dysfunction, decreased mitochondrial density and defects in mitochondrial dynamics, but Tctp knockdown embryos have intact mitochondrial biogenesis and mass, arguing for a phenotype with pre- dominantly axonal repercussions. Furthermore, I document that axonal Tctp interacts with Bcl-2 pro-survival oncoproteins myeloid cell leukemia 1 (Mcl1) and Bcl-2-like protein 1 (Bcl-XL), and that Caspase-3 activation and increased P53 levels are found in growth cones depleted of Tctp. Overall, the data I have collected over the course of my research indicate that Tctp regulates axon development by impacting on the homeostatic mechanisms of the neuron. My findings thus suggest a novel and fundamental role for Tctp in vertebrate neural circuitry formation.
Com os seus cerca de 86 mil milhões de neurónios [1], o cérebro humano é constituído por uma rede intrincada de processos axonais e dendríticos complexamente interligados, e que, como um todo coerente, nos permite reconhecer sinais com origem no meio externo e responder de forma consciente sobre este. A formação de ligações precisas entre as diversas áreas do sistema nervoso assume, portanto, um papel fundamental no garante das suas funções. Numa primeira fase, os programas de conectividade neuronal desenvolvem-se no decurso da embriogénese. Em concreto, após a formação e subsequente migração do neurónio, este estende um axónio que se expande de modo estereotipado até à vizinhança do seu alvo pós-sináptico. Os mecanismos de navegação axonal dependem de uma sequência de marcos moleculares distribuídos pelo sistema nervoso embrionário, os quais são integrados ao nível do cone de crescimento, uma estrutura ameboide com capacidades sensoriais e motoras, existente no extremo distal do axónio. Ao longo das últimas três décadas, um vasto leque de estudos foi permitindo perceber que o cone de crescimento é dotado de um certo grau de autonomia funcional [2], facto claramente ilustrado pela capacidade inalterada revelada por axónios embrionários seccionados – isto é, separados dos seus corpos celulares – para se orientarem corretamente in vivo [3]. Sabe-se hoje que esta flexibilidade de atuação advém, em parte, da regulação local do proteoma axonal promovida pelos sinais moleculares presentes no meio extracelular embrionário. A tradução local de novas proteínas despoletada por estes factores permite, por exemplo, alterações rápidas ao nível do citoesqueleto [4-6] e da expressão de receptores na membrana celular do cone de crescimento [7], assim como potenciar mecanismos de manutenção axonal e mitocondrial [8-10]. É, no entanto, o carácter transversal do transcriptoma axonal – o número de espécies de ARNm localizados no compartimento axonal situa-se na ordem dos milhares [11-15] – que porventura nos dá verdadeiramente conta da importância funcional deste processo celular. Nos estudos laboratoriais conducentes a esta tese, foi estudada a participação da Tctp (do acrónimo inglês, translationally controlled tumor protein) nos processos de conectividade neuronal, usando como modelo a projeção retinotectal da rã-de-unhas -africana (Xenopus laevis). A Tctp é uma proteína conservada filogeneticamente [16], relevante ao nível de processos de sobrevivência [17] e de crescimento celular [18, 19], e bem caracterizada em particular no âmbito da oncogénese [20]. A motivação inicial para estudar a Tctp neste contexto surgiu da identificação do ARNm que codifica a Tctp entre os mais abundantemente expressos no compartimento axonal de diversas populações neuronais [11-14], incluindo em células ganglionares da retina, indicando que esta proteína detém um papel local relevante, mas por explorar, no campo da neurobiologia. A minha contribuição original mais significativa para o conhecimento prende-se com a identificação do envolvimento da Tctp na regulação do desenvolvimento axonal através da sua função de suporte à homeostasia mitocondrial. Especificamente, a depleção da Tctp durante a embriogénese resulta em projeções retinotectais que não granjeiam alcançar a zona-alvo no mesencéfalo aquando do estádio de desenvolvimento normal. Os axónios deficitários em Tctp apresentam uma disfunção e menor densidade mitocondrial, bem como dinâmicas de transporte mitocondrial alteradas; contudo, tais manifestações não se traduzem em decréscimos globais da biogénese ou da massa destes organelos, pelo que se infere um fenótipo com repercussões predominantemente axonais. Documento ainda a interação intra-axonal da Tctp com duas oncoproteínas anti-apoptóticas da família Bcl-2 – a Mcl1 (do acrónimo inglês, myeloid cell leukemia 1) e a Bcl-XL (Bcl-2-like protein 1) – e aumentos nos níveis de expressão da P53 e da forma ativada da Caspase-3 no cone de crescimento de axónios desprovidos da Tctp. Estes resultados indicam que a Tctp regula o desenvolvimento axonal pela sua ação nos mecanismos de homeostasia celular. O meu estudo sugere, portanto, que à Tctp cabe uma função de fundamental relevância nos mecanismos de formação dos circuitos neuronais em vertebrados.
FCT- SFRH/BD/33891/2009