Dissertations / Theses on the topic 'Lysosomal storage disorder (LSD)'

Mucopolysaccharidosis type IIIB (MPSIIIB) is a lysosomal storage disease (LSD) characterized by accumulation of heparan sulfate oligosaccharides (HSO), which results in progressive mental retardation, neurodegeneration and premature death in children. The underlying mechanisms are poorly understood. Coming to a better understanding of the pathophysiology of MPSIIIB has become a necessity to assess the efficacy of gene therapy treatment regarding loss of neuronal plasticity, and to define the best conditions for treatment. To address the link between HSO accumulation and downstream pathological events, new cell models of MPSIIIB were created. First, induced pluripotent stem cells (iPSc) were generated from fibroblasts of affected children, followed by differentiation of patient-derived iPSc into a neuronal progeny. Second, a HeLa cell model was created in which expression of shRNAs directed against a-N-acetylglucosaminidase (NAGLU), the deficient enzyme in MPSIIIB, is induced by tetracycline. Success in the isolation of these different models was pointed by the presence of cardinal features of MPSIIIB cell pathology. Studies in these models showed that: I) HSO excreted in the extracellular matrix modifies cell perception of environmental cues, affecting downstream signalling pathways with consequences on the Golgi morphology. II) Accumulation of intracellular storage vesicles, a hallmark of LSDs is due to overexpression of the cis-Golgi protein GM130 and subsequent Golgi alterations. It is likely that these vesicles are abnormal lysosomes formed in the cis- and medial-Golgi which are misrouted at an early step of lysosome biogenesis, giving rise to a dead-end compartment. III) Other cell functions controlled by GM130 are affected, including centrosome morphology and microtubule nucleation. These data point to possible consequences on cell polarization, cell migration and neuritogenesis.

Metachromatic leukodystrophy (MLD) and Gaucher disease (GD) are caused by a deficiency of arylsulphatase A (ASA) and b-glucocerebrosidase (GBA), respectively. They are lysosomal storage disorders with a heterogeneous clinical spectrum encompassing visceral, skeletal and neurologic involvement resulting in high morbidity and mortality. The overall aim of this study is to elucidate the genetic component/s of high ASA and GBA enzyme activity in normal healthy individuals with the ultimate goal of using this information to produce greater protein activity from a recombinant protein. A wide variation in ASA and GBA enzyme activity levels has been observed in the normal population. The first objective of this project was to identify and characterise single nucleotide polymorphisms (SNPs) in the arylsulphatase A (ARSA) and glucocerebrosidase (GBA) genes that are responsible for determining the levels of expressed enzyme activity in the normal population. The second objective was to assess the contribution of transcriptional regulation and TCP80 mediated translational control to normal enzyme variation. TCP80, a translational control protein that interacts with the GBA coding region, is a splice variant of the interleukin binding factor 3 (ILF3) gene. Ten samples from individuals with high ASA activity and twenty samples from individuals with high GBA activity were screened for polymorphisms via denaturing high pressure liquid chromatography (dHPLC) and sequencing. The frequency of these polymorphisms in the normal population was determined using dot-blot hybridisation. Fifteen ARSA polymorphisms (4 promoter, 5 coding, 5 intronic and 1 poly(A) signal) and two GBA polymorphisms (1 intronic and 1 in 3¢-UTR) were identified. Two low frequency ASA polymorphisms (2723A > G, W193C) were found to be correlated with low activity, while another low frequency ASA polymorphism (1101+123C > T) was found to be correlated with high activity in a population of 113 individuals. Real time PCR was used to measure mRNA levels of GBA, ASA and LF3 along with enzyme activity levels of GBA and ASA in two cell types (leucocytes and skin fibroblasts) from four healthy individuals and seven cell lines (HL60, THP1, Huh7, U118, SW1353, Hep G2, and B-cells). Transcriptional control was evident for all three genes with GBA mRNA levels varying over 30 fold, ASA mRNA levels varying over seven fold and ILF3 levels varying more than 24 fold. The 5¢-flanking region of GBA was investigated for the cis-elements responsible for tissue-specific expression. However, it was not possible to demonstrate that the cis-element region was influencing GBA expression. Translational efficiency was measured using the magnitude of the mRNA:enzyme activity ratio as an indicator. GBA translational inefficiency was most pronounced in B cells which require four times more mRNA molecules than hepatocytes (Hep G2) and over 25 times more mRNA molecules than chondrocytes (SW1353) to produce one unit of GBA enzyme activity. Except in B-cells, GBA translational efficiency appears to increase as ILF3 mRNA levels decrease. The tissue-specific variation observed in the protein levels of the ILF3 splice variants, TCP80 and DRBP76, may play a role. The correlation of several low frequency SNPs with low ASA enzyme activity or high ASA activity indicates a role in determining the distribution of enzyme activity levels in the normal population. However, there do not appear to be any common high activity polymorphisms. Knowledge of the exact mechanisms responsible for the observed transcriptional and translational control of these lysosomal genes will greatly enhance the understanding of genotype-phenotype correlation and the contribution of genetic variants to natural variation.

Metachromatic leukodystrophy (MLD) and Gaucher disease (GD) are caused by a deficiency of arylsulphatase A (ASA) and b-glucocerebrosidase (GBA), respectively. They are lysosomal storage disorders with a heterogeneous clinical spectrum encompassing visceral, skeletal and neurologic involvement resulting in high morbidity and mortality. The overall aim of this study is to elucidate the genetic component/s of high ASA and GBA enzyme activity in normal healthy individuals with the ultimate goal of using this information to produce greater protein activity from a recombinant protein. A wide variation in ASA and GBA enzyme activity levels has been observed in the normal population. The first objective of this project was to identify and characterise single nucleotide polymorphisms (SNPs) in the arylsulphatase A (ARSA) and glucocerebrosidase (GBA) genes that are responsible for determining the levels of expressed enzyme activity in the normal population. The second objective was to assess the contribution of transcriptional regulation and TCP80 mediated translational control to normal enzyme variation. TCP80, a translational control protein that interacts with the GBA coding region, is a splice variant of the interleukin binding factor 3 (ILF3) gene. Ten samples from individuals with high ASA activity and twenty samples from individuals with high GBA activity were screened for polymorphisms via denaturing high pressure liquid chromatography (dHPLC) and sequencing. The frequency of these polymorphisms in the normal population was determined using dot-blot hybridisation. Fifteen ARSA polymorphisms (4 promoter, 5 coding, 5 intronic and 1 poly(A) signal) and two GBA polymorphisms (1 intronic and 1 in 3¢-UTR) were identified. Two low frequency ASA polymorphisms (2723A > G, W193C) were found to be correlated with low activity, while another low frequency ASA polymorphism (1101+123C > T) was found to be correlated with high activity in a population of 113 individuals. Real time PCR was used to measure mRNA levels of GBA, ASA and LF3 along with enzyme activity levels of GBA and ASA in two cell types (leucocytes and skin fibroblasts) from four healthy individuals and seven cell lines (HL60, THP1, Huh7, U118, SW1353, Hep G2, and B-cells). Transcriptional control was evident for all three genes with GBA mRNA levels varying over 30 fold, ASA mRNA levels varying over seven fold and ILF3 levels varying more than 24 fold. The 5¢-flanking region of GBA was investigated for the cis-elements responsible for tissue-specific expression. However, it was not possible to demonstrate that the cis-element region was influencing GBA expression. Translational efficiency was measured using the magnitude of the mRNA:enzyme activity ratio as an indicator. GBA translational inefficiency was most pronounced in B cells which require four times more mRNA molecules than hepatocytes (Hep G2) and over 25 times more mRNA molecules than chondrocytes (SW1353) to produce one unit of GBA enzyme activity. Except in B-cells, GBA translational efficiency appears to increase as ILF3 mRNA levels decrease. The tissue-specific variation observed in the protein levels of the ILF3 splice variants, TCP80 and DRBP76, may play a role. The correlation of several low frequency SNPs with low ASA enzyme activity or high ASA activity indicates a role in determining the distribution of enzyme activity levels in the normal population. However, there do not appear to be any common high activity polymorphisms. Knowledge of the exact mechanisms responsible for the observed transcriptional and translational control of these lysosomal genes will greatly enhance the understanding of genotype-phenotype correlation and the contribution of genetic variants to natural variation.

Mucopolysaccharidosis type III (Sanfilippo) is comprised of four phenotypically similar lysosomal storage disorders (MPS IIIA-D) caused by the deficiency of enzymes that catabolise heparan sulphate (HS). Progressive accumulation of HS results in abnormal behaviour, progressive cognitive and motor impairment and death in mid-teens. There are currently no treatments for MPS III. To assess the effect of novel therapeutics in the mouse models of MPS III it is necessary to examine the effect on primary storage of HS, secondary storage and behaviour. The reported behaviour of MPS IIIA and B mice is conflicting therefore we developed a one-hour open field test, performed at the same time of day during a period of hyperactivity observed in a previous circadian rhythm study of MPS IIIB mice. At 8 months of age MPS IIIB mice were hyperactive, with increased rapid exploratory behaviour and a reduction in immobility time. The MPS IIIA mice presented with the same behavioural phenotype as the MPS IIIB mice and were significantly hyperactive at 4 and 6 months of age and also displayed a reduced sense of danger. The hyperactivity and reduced sense of danger observed in the mice is consistent with the patient phenotype. Whilst haematopoietic stem cell transplant (HSCT) is the standard therapy used to treat the similar HS storage disorder MPS I Hurler, it is ineffectual in MPS IIIA. We hypothesise that HSCT failure in MPS IIIA is due to insufficient enzyme production in the brain by donor-derived microglial cells. By increasing expression of N-sulphoglucosamine sulphohydrolase (SGSH) we may be able to treat MPS IIIA. Therefore we compared the effect of HSCT using normal haematopoietic stem cells (WT-HSCT) to lentiviral overexpression of SGSH in normal cells (LV-WT-HSCT) or MPS IIIA cells (LV-IIIA-HSCT) in MPS IIIA mice, using the behavioural tests developed.SGSH activity in the brain of MPS IIIA recipients was not significantly increased by WT-HSCT, but was significantly increased by LV-IIIA-HSCT and LV-WT-HSCT. HS was significantly reduced by all transplants but the best treatment was LV-WT-HSCT. Neuroinflammation, indicated by the number of microglia in the brain, was significantly reduced by all treatments but remains significantly elevated. GM2 gangliosides were significantly reduced by WT-HSCT and LV-WT-HSCT and were no longer significantly elevated, but LV-IIIA-HSCT had no significant effect. Critically LV-WT-HSCT corrected the behaviour at 4 and 6 months of age whilst the other treatments had no significant effect. LV-WT-HSCT and WT-HSCT reduced GM2 gangliosides and neuroinflammation equally but only LV-WT-HSCT corrected behaviour and primary HS storage, suggesting they are the important factors in MPS IIIA pathology. LV-WT-HSCT corrects the neurological phenotype in MPS IIIA mice and is a clinically viable approach to treat MPS IIIA and other neuropathic lysosomal storage disorders.

Mutations in MCOLN1, which encodes the cation channel protein TRPML1, result in the neurodegenerative lysosomal storage disorder Mucolipidosis type IV. Mucolipidosis type IV patients show lysosomal dysfunction in many tissues and neuronal cell death. The orthologue of TRPML1 in Caenorhabditis elegans is CUP-5; loss of CUP-5 results in lysosomal dysfunction in many tissues and death of developing intestinal cells that results in embryonic lethality. We previously showed that a null mutation in the ATP-Binding Cassette transporter MRP-4 rescues the lysosomal defect and embryonic lethality of cup-5(null) worms. Here we show that reducing levels of the Endosomal Sorting Complex Required for Transport (ESCRT)-associated proteins DID-2, PHI-33, and ALX-1/EGO-2, which mediate the final de-ubiquitination step of integral membrane proteins being sequestered into late endosomes, also almost fully suppress cup-5(null) mutant lysosomal defects and embryonic lethality. Indeed, we show that MRP-4 protein is hypo-ubiquitinated in the absence of CUP-5 and that reducing levels of ESCRT-associated proteins suppresses this hypo-ubiquitination. Thus, increased ESCRT-associated de-ubiquitinating activity mediates the lysosomal defects and corresponding cell death phenotypes in the absence of CUP-5.

Master of Science
Biochemistry and Molecular Biophysics Interdepartmental Program
Stella Yu-Chien Lee
Neuronal ceroid lipofuscinoses (NCLs) are a group of neurodegenerative lysosomal storage disorders which is the most frequent group of inherited neurodegenerative disorders that affect children leading to severe pathological conditions such as progressive loss of motor neuron functions, loss of vision, mental retardation, epilepsy, ataxia and atrophy in cerebral, cerebella cortex and retina and eventually premature death. Among the many genes that cause NCL, mutations in CLN5 leads to different forms of NCL (infantile, late infantile, juvenile and adult) and mutations in CLN8 leads to progressive epilepsy with mental retardation (EPMR) and a variant late infantile form of NCL. The function(s) of both CLN5 and CLN8 proteins remain elusive. CLN5 is a glycosylated soluble protein that resides in the lysosome. We observed that endogenous CLN5 protein exist in two forms and identified a previously unknown C-terminal proteolytic processing event of CLN5. Using a cycloheximide chase experiment we demonstrated that the proteolytic processing of CLN5 is a post-translational modification. Furthermore treatment with chloroquine showed the processing occurs in low pH cellular compartments. After treatment with different protease inhibitors our results suggested the protease involved in the processing of CLN5 could be a cysteine protease. Using two glycosylation mutants of CLN5, retained in the endoplasmic reticulum (ER) or the Golgi we showed the proteolytic processing occurs in an organelle beyond the ER. This study contributes to understanding the characteristics of the CLN5 protein. CLN8 is an ER resident transmembrane protein that shuttles between the ER and the ER-Golgi intermediate compartment (ERGIC). In our study we identified a potential interaction between CLN8 and a PP2A holoenzyme complex consisting regulatory subunit A α isoform and regulatory subunit B α isoform. Using two CLN8 patient derived fibroblast cell lines we were able to show that the phosphorylated levels of PP2A target kinase Akt was reduced at both of its regulatory sites Ser473 and Thr308 and the activity of PP2A was increased. A delay of ceramide transport from ER to Golgi in CLN8 deficient patient cell lines was observed using BODIPY FL C5-Ceramide staining. Our results provide evidence for CLN8 protein being involved in the regulation of PP2A activity and trafficking of ceramide from ER to Golgi.

Astrocytes are the most abundant cellular population in the brain and their role in neurodegenerative processes is becoming increasingly appreciated. In my PhD project, I investigated the contribution of astrocytes to neurodegeneration in Multiple Sulfatase Deficiency (MS D), a severe Lysosomal Storage Disorder (LSD) caused by mutations in the Sulfatase Modifying Factor 1 (SUMF1) gene. Using Cre/Lox mouse models, I found that astrocyte-specific deletion of Sumf1 in vivo induced severe lysosomal storage and autophagy dysfunction with consequential cytoplasmic accumulation of toxic substrates. Lysosomal storage in astrocytes was sufficient to induce degeneration of cortical neurons in vivo, whereas other neuronal populations were spared. Furthermore, in an ex vivo co-culture assay, I observed that Sumf1-/- astrocytes failed to support the survival and function of wild type cortical neurons, suggesting a non-cell autonomous mechanism for neurodegeneration in LSDs. Compared to the astrocyte-specific deletion of Sumf1, the concomitant deletion of Sumf1 in both neurons and glia in vivo induced a widespread neuronal loss and robust neuroinflammation. Finally, behavioural analysis of mice with astrocyte-specific deletion of Sumf1 compared to mice with Sumf1 deletion in both astrocytes and neurons allowed me to link a subset of neurological manifestations of LSDs to astrocyte dysfunction. This study indicates that astrocytes are integral components of the neuropathology in LSDs and that modulation of astrocyte function may impact the disease course.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Biology, February 2002.
Includes bibliographical references.
The process of programmed cell death is important in the development and homeostasis of multicellular organisms. The conserved morphological events of this process have been termed apoptosis. The molecular mechanisms of apoptosis execution are also conserved. We have investigated the behavior of these shared components during programmed cell death in the nematode Caenorhabditis elegans. We have found that the CED-9 protein, an anti-apoptotic member of the Bcl-2 family of apoptotic regulators, is required for the sequestering of the CED-4 cell-death activator to mitochondria. In the absence of CED-9 in C. elegans embryos, we found that CED-4 protein translocates to the nuclear membrane. In addition, inducing excess programmed cell death by expression of the EGL-1 cell-death activator triggers the translocation of CED-4 from mitochondria to the nuclear membrane. We performed a genetic screen for mutations that trigger programmed cell death in ced-9 gain-of-function animals where cell death is blocked. We identified a mutation in cup-5, the C. elegans homolog of the human mucolipidosis type IV gene, which is mutated in a lysosomal storage disorder. We found that cup-5 is required for viability and that excess lysosomes accumulate in cup-5 mutants. In addition, cup--5 mutants contain excess programmed cell deaths, suggesting that apoptosis may play a role in the pathology of mucolipidosis type IV.
by Bradley Michael Hersh.
Ph.D.

Master of Science
Department of Biology
Stella Y. Lee
CLN5 is one of several proteins that when mutated result in the lysosomal storage disorder (LSD) Neuronal Ceroid Lipofuscinosis (NCL). CLN5 is a soluble lysosomal protein that has no known function at this time. Previously we showed that eight asparagine residues in CLN5 are N-glycosylated, and that this modification is important for the protein’s transport and function. Now, we have identified a link between the activation of autophagy and CLN5 deficiency. The autophagy-lysosomal protein degradation system is one of the major pathways the cell uses to degrade intracellular material and recycle cellular building blocks. It was recently shown that other CLN proteins affect the relative level of autophagy, indicating a potential link between the autophagy pathway and the NCLs. By knocking down endogenous CLN5 in HeLa we showed that, upon stress induction, cells responded with higher levels of autophagy activation. Consistent with these knockdown experiments, there is a higher level of the autophagy marker protein, LC3-II, in CLN5 patient cells that are naturally deficient for the CLN5 protein. Pharmaceutical induction of autophagy through different means also showed higher LC3-II levels compared to control, though patterns differed in the type of autophagy induced. In summary, we discovered that the autophagy pathway is altered in CLN5 deficient cells, indicating a potential role for CLN5 in autophagy. Further analyses of the autophagy pathway will shed light on where CLN5 is acting and the mechanism by which defective CLN5 causes NCL.

La thérapie chaperon représente une approche thérapeutique stratégique et innovante, en particulier dans le traitement des maladies lysosomales. Ces maladies génétiques rares ont une gravité variable, qui peut aller de la létalité avant la naissance jusqu’à la nécessité d‟une prise en charge permanente ; elles apparaissent à tous les stades de la vie. Des mimes du substrat appelé iminosucres, vont agir en allant au coeur du site actif de l’enzyme, stabiliser l’enzyme mutée qui est instable mais non inactive. Paradoxalement, la plupart des chaperons pharmacologiques sont des inhibiteurs de l’enzyme visée mais leur administration à faible concentration leur permet de réaliser leur mission de sauvetage de l’enzyme mutée. Dans cette optique, des recherches effectuées au sein de notre laboratoire ont fait état de la synthèse d’iminosucres, tels que les α-1-C-alkyl iminoxylitols qui sont de très bons inhibiteurs de la β-glucocérébrosidase, l’enzyme défaillante dans la maladie de Gaucher, mais aussi qui doublent l’activité enzymatique résiduelle. Une nouvelle voie de synthèse plus efficace a été réalisée afin d’obtenir plus efficacement ce type d’iminosucres et d’autres dérivés. Ces travaux ont également été l’occasion de développer des iminoxylitols structurellement simplifiés qui agissent comme chaperons pharmacologiques toujours pour le traitement de la maladie de Gaucher. Une partie de ces travaux a aussi été consacrée à la recherche d‟inhibiteurs de la β-galactocérébrosidase, l’enzyme impliquée dans la maladie de Krabbé, et qui pourront agir comme chaperons pharmacologiques. Différentes évaluations pharmacologiques ont été réalisées, notamment des tests d’inhibition et la détermination des effets chaperons
Chaperone Mediated Therapy represents an innovative and strategic approach to treat lysosomal storage disorders which a class of rare genetic diseases. Competitive inhibitors for some of these lysosomal enzymes can, at sub inhibitory concentrations, act as chaperones and rescue the mutant proteins. In fact, enzymes carrying some mutations are still catalytically active. α-1-C-alkyl iminoxylitols represent a class of iminosugars which mimic the “gluco” configuration of the substrate and give powerful inhibitors of β-glucocerebrosidase, the enzyme involved in Gaucher disease. Moreover, this class of iminosugars, synthesized by our group, act as pharmacological chaperones and are able to double the residual activity of the N370S mutant. In order to synthesize more efficiently these iminosugars, the synthetic strategy was improved and optimized. Moreover, we focused our investigations on structural variations on our lead compound (α-1-C9 iminoxylitol) and draw important conclusions on structure-activity relationship. Then, we extended our expertise on iminosugars as pharmacological chaperones to another lysosomal glycosidase. In paricular, we targeted β-galactocerebrosidase, the enzyme responsible for Krabbe disease, and synthesized a series of iminosugars which mimic the “galacto” configuration. Biological assays were performed on our compounds to determine their activity as inhibitors and for some of them, their chaperone effects

Our research aims at understanding the roles of seminolipid (sulfogalactosylglycerolipid or SGG) and its associated membrane domains in male reproduction. SGG is a sulfoglycolipid present selectively and abundantly in mammalian male germ cells. Therefore, information on its properties would be relevant towards the development of male fertility biomarkers and spermicide-based contraceptives. We have shown that SGG has direct affinity for zona pellucida (ZP, egg extracellular matrix) and plays a role in the formation of sperm lipid rafts, the ZP-binding platforms on the sperm anterior head plasma membrane (APM), the initial ZP binding site. For a better understanding of mechanisms underlying sperm-ZP interaction, I performed proteomic characterization of APM vesicles (SGG-associated membrane domains with ZP affinity) isolated from sperm before and after capacitation, a process through which sperm gain maximal ZP affinity. Proteomic results revealed that capacitated APM vesicles contained high-molecular-weight protein complexes, with higher ZP affinity and levels of ZP-binding proteins as compared with those of the non-capacitated samples. ZP-binding proteins known to exist in the acrosome (i.e., zonadhesin, proacrosin/acrosin) were found in these APM protein complexes. Immunofluorescence suggested that a fraction of these proteins trafficked from the acrosome to APM during capacitation. These findings provided a new mechanism on how sperm gain full ZP-binding ability during capacitation. Since SGG is a major component of APM, proper SGG levels at this site would be important for male fertility. Levels of sperm SGG are regulated through the synthesis and degradation. In fact, lack of SGG-synthesis enzymes causes a spermatogenesis disruption, resulting in male infertility. However, significance of SGG degradation remains unknown. SGG can be desulfated in vitro by arylsulfatase A (ARSA), an enzyme existing in the acrosomes of sperm/spermatids and lysosomes of Sertoli cells, testicular somatic cells that nurture developing germ cells. Sertoli cells also phagocytose ~50% of germ cells that become apoptotic during spermatogenesis. To understand physiological importance of SGG degradation, the fertility status and SGG levels of Arsa-/- male mice were determined. We found that Arsa-/- males became subfertile when they were older than 5 months, and when they were 8-month-old (~40-year-old men) they produced sperm at 50% wild type rate. Arsa-/- sperm had minimal in vitro fertilizing ability and a number of them showed abnormal morphology. Quantitative mass spectrometry revealed that SGG levels in Sertoli cells of 8-month-old Arsa-/- mice were increased to ~250% of the wild type level; this SGG accumulation may lead to a decrease in Sertoli cell ability to support spermatogenesis. However, SGG levels in sperm of 8-month-old Arsa-/- mice were ~50% of the wild type value, a result that partly explained the decreased fertilizing ability of these sperm. The reduced SGG level of Arsa-/- sperm was likely due to a lack of SGG’s building-block lipid (palmitylpalmitoylglycerol) putatively generated in Arsa-/- Sertoli cells and recycled to the next generation of primary spermatocytes for SGG synthesis. Hence, levels of sperm SGG are a promising bioindex for male fertility. Since Sertoli cells also regulate SGG homeostasis, their functionality should be now included in male fertility/subfertility diagnosis.

Les glycosidases sont des enzymes impliquées dans de nombreux processus biologiques. Entre autres, elles sont responsables de la dégradation des déchets polysaccharidiques de nos cellules. Lorsqu'une modification génétique touche un gène qui code pour une de ces enzymes, des pathologies graves regroupées sous l'appellation de " maladies lysosomales " peuvent être déclenchées. L'objectif de ce projet a été de proposer une méthode de synthèse efficace de molécules potentiellement actives spécifiquement sur l'une ou l'autre de ces maladies. Les molécules ciblées sont des inhibiteurs de glycosidases de la famille des aminocyclitols, utilisés dans une stratégie thérapeutique émergente " par molécules chaperonnes ". La méthode de synthèse développée s'appuie sur une étape enzymatique clé utilisant les aldolases comme catalyseurs et répondant aux contraintes environnementales actuelles de la chimie verte. Nous avons atteint nos objectifs grâce à l'utilisation de trois aldolases différentes, produites et purifiées pour la première fois au sein de notre laboratoire. Il s'agit de la fuculose-1-phosphate aldolase F1PA, de la rhamnulose-1-phosphate aldolase R1PA et de la nouvellement découverte fructose-6-phosphate aldolase FSA. La formation d'une quarantaine de nitrocyclitols, de stéréochimies définies, précurseurs des aminocyclitols correspondant, a ainsi été réalisée avec de très bons rendements de synthèse.

Alzheimer’s disease, the most common form of dementia, is characterised by extracellular amyloid beta plaques and intraneuronal tau tangles. While it is not fully understood why these pathological hallmarks develop, several biological systems are believed to be involved. Of these, lysosomal network dysfunction is an increasingly recognised pathogenic factor. Lysosomal network disruptions, including upregulated endocytosis, aberrant trafficking and storage of undegraded substrates, commence from the earliest stages of Alzheimer’s disease. The importance of the lysosomal network for neuronal health is underscored by the existence of more than 50 lysosomal storage disorders, which arise from the deficiency of an enzyme or other protein required for lysosomal function. Many lysosomal storage disorders have a severe neurodegenerative phenotype, most are recessively inherited, and until recently, heterozygotes were considered asymptomatic carriers. However, there is increasing evidence of some pathophysiology in heterozygotes, especially during ageing. This study aimed to investigate the impact of a heterozygous lysosomal storage disorder allele (Hexb+/-) in an Alzheimer’s mouse model (AppNL-G-F/NL-G-F). We hypothesised Hexb heterozygosity would hasten and/or exacerbate pathology and disease-related signs in AppNL-G-F/NL-G-F mice. The AppNL-G-F/NL-GF knock-in mouse was novel and not extensively characterised at the beginning of this PhD study. We therefore performed a behavioural test battery, and examined the lysosomal network, in six-monthold AppNL-G-F/NL-G-F mice. AppNL-G-F/NL-G-F mice did not have memory impairments detectable in a Y-maze, novel object recognition test or Morris water maze at six-months. They did, however, exhibit reduced open field activity and lysosomal network disruptions. Lysosome-associated membrane protein 1 and cathepsins B, L and D accumulated at amyloid beta plaques in AppNL-G-F/NL-G-F mice, presenting at the earliest and smallest plaques observed. AppNL-G-F/NL-G-F mice also exhibited elevated activity of β- hexosaminidase and cathepsins D/E and elevated levels of cathepsin D and LC3-II in the cerebral cortex, as determined by Western blot. AppNL-G-F/NL-G-F mice were intercrossed with Hexb+/- mice to determine the effect of heterozygosity of Hexb in the Alzheimer’s mouse. No substantial memory impairments or increases in key neuropathological markers of Alzheimer’s disease were found. However, AppNL-G-F/NL-G-F; Hexb+/- mice demonstrated subtle impairments in behavioural flexibility during the reversal phase of the Morris water maze. AppNL-G-F/NL-G-F; Hexb+/+ mice had reduced activity in an open field and on the Y-maze. This phenotype was not exacerbated in AppNL-G-F/NL-G-F; Hexb+/- mice, but was reproduced by Hexb heterozygosity alone, in Appwt/wt; Hexb+/- mice. Heterozygosity of Hexb in AppNL-G-F/NL-G-F mice did not increase glial fibrillary acidic protein or ionised calcium binding adaptor molecule 1, markers of astrocytes and microglia, respectively. Nor did it lead to increased GM2 ganglioside (the substrate degraded by the enzyme encoded by Hexb), or related gangliosides, GM1 or GM3. Surprisingly, heterozygosity of Hexb resulted in less amyloid beta plaques in the orbital cortex and hippocampus of 46-week-old AppNL-G-F/NL-G-F mice and less Aβ42 in the hippocampus. In summary, Hexb heterozygosity in AppNL-G-F/NL-G-F mice did not induce substantial memory impairments or increase key neuropathological markers of Alzheimer’s disease, but led to subtle phenotypic alterations, suggesting that Hexb haploinsufficiency is not a dominant factor in the progression of Alzheimer’s disease.
Thesis (Ph.D.) -- University of Adelaide, Adelaide Medical School, 2020

A doença de Gaucher é uma doença rara, autossómica recessiva, que resulta de uma acumulação anormal de uma substância lipídica, conhecida como glucocerebrosídeo ou glucosilceramida. Normalmente, o glucocerebrosídeo é metabolizado pela enzima glucocerebrosidase (ou β-glucosidase ácida). São as mutações no gene da glucocerebrosidase 1, a causa mais prevalente de todas as formas da doença de Gaucher. Essa alteração genética significa que a enzima não funciona corretamente ou está totalmente ausente. Isso, por sua vez, leva à acumulação de glucocerebrosídeo nas células. É por causa desta aglomeração que a doença de Gaucher é chamada de distúrbio de armazenamento e, como o acúmulo ocorre no lisossoma, é uma desordem de armazenamento lisossomal (também conhecida como doença de armazenamento lisossomal, ou esfingolipidose), em que esse excesso de lípidos acontece nos macrófagos. A acumulação de lípidos nas células na doença de Gaucher é diferente para cada pessoa, o que acarreta uma desigual sintomatologia que varia consideravelmente de paciente para paciente. Algumas pessoas apresentam sintomas graves na infância, enquanto que outras não apresentam sintomas ou apresentam apenas sintomas leves e são diagnosticadas numa fase mais tardia da vida. Pacientes com doença de Gaucher podem manifestar danos neurológicos. Três tipos principais da doença de Gaucher têm vindo a ser descritos ao longo dos tempos, com base na ausência (tipo 1), presença (tipo 2 e tipo 3) ou da gravidade das características neurológicas. Um fenómeno multissistémico complexo surge envolvendo o fígado, baço, medula óssea e, ocasionalmente, os pulmões, havendo ainda casos de doença neurodegenerativa progressiva. O tratamento de reposição enzimática tornou-se o padrão de terapia em 1991, transformando a história natural da doença de Gaucher. Atualmente, tratamentos para doença de Gaucher, clinicamente usados para o tipo sistémico da doença, incluem a terapia enzimática de substituição, a terapia de redução de substrato e o transplante de células-tronco hematopoéticas, embora a última seja a única opção de sucesso para os tipos neuronopáticos da Doença de Gaucher. Este trabalho tem como objetivo fazer uma revisão narrativa da doença de Gaucher, contemplando, em particular, o tratamento usado.
Gaucher disease is a rare, autosomal recessive disease that results from an abnormal accumulation of a lipid substance known as glucocerebroside or glucosylceramide. Normally, glucoderebroside is metabolized by the enzyme glucocerebrosidase (or acid β-glucosidase). The mutations in the glucocerebrosidase 1 gene, are the most prevalent cause of all forms of Gaucher disease. This genetic alteration means that the enzyme does not work properly or is completely absent. This, in turn, leads to the accumulation of glucocerebroside in cells. It is because of this clumping that Gaucher disease is called a storage disorder and, as the accumulation occurs in the lysosome, it is a lysosomal storage disorder (also know as lysosomal storage disease, or sphingolipidosis) in which this excess of lipids happens in macrophages. The accumulation of lipids in cells in Gaucher disease is different for each person, resulting in unequal symptomatology that varies considerably from patient to patient. Some people have severe symptoms in childhood, while others have no symptoms or only mild symptoms and are diagnosed later in life. Gaucher disease patients may manifest neurological damage, three main types of Gaucher disease have been described over time, based on the absence (type 1), presence (type 2 and type 3) or the severity of neurological characteristics. A complex multisystem phenomenon arises involving the liver, spleen, bone marrow and, occasionally, the lungs, with cases of progressive neurodegenerative disease still occurring. Enzyme replacement treatment became the standard of therapy in 1991, transforming the natural history of Gaucher disease. Currently, treatments for Gaucher disease, clinically used for the systemic type of disease, include enzyme replacement therapy, substrate reduction therapy, and hematopoietic stem cell transplantation, although the latter is the only successful option for patients with the neuronopathic types of Gaucher disease. This work aims to make a narrative review of Gaucher disease, considering, in particular, the treatment used.