Academic literature on the topic 'Src-family kinases (SFKs)'

Src family kinases (SFKs) belong to nonreceptor protein tyrosine kinases and have been implicated in the regulation of numerous cellular processes, including cell proliferation, differentiation, migration and invasion, and angiogenesis. The role and mechanisms of SFKs in tumorgenesis have been extensively investigated, and some SFK inhibitors are currently under clinical trials for tumor treatment. Recent studies have also demonstrated the importance of SFKs in regulating the development of various fibrosis-related chronic diseases (e.g., idiopathic pulmonary fibrosis, liver fibrosis, renal fibrosis, and systemic sclerosis). In this article, we summarize the roles of SFKs in various chronic kidney diseases, including glomerulonephritis, diabetic nephropathy, human immunodeficiency virus-associated nephropathy, autosomal dominant form of polycystic kidney disease, and obesity-associated kidney disease, and discuss the mechanisms involved.

SRC family kinases (SFKs) are known regulators of multiple cellular events, including cell movement, differentiation, proliferation, survival and apoptosis. SFKs are expressed virtually by all mammalian cells. They are non-receptor protein kinases that phosphorylate a variety of cellular proteins on tyrosine, leading to the activation of protein targets in response to environmental stimuli. Among SFKs, SRC, YES and FYN are the ubiquitously expressed and best studied members. In fact, SRC, the prototypical SFK, was the first tyrosine kinase identified in mammalian cells. Studies have shown that SFKs are regulators of cell junctions, and function in endocytosis and membrane trafficking to regulate junction restructuring events. Herein, we briefly summarize the recent findings in the field regarding the role of SFKs in the testis in regulating spermatogenesis, particularly in Sertoli–Sertoli and Sertoli–germ cell adhesion. While it is almost 50 years since the identification of the oncogene v-Src encoded by Rous sarcoma transforming virus, the understanding of SFK involvement during spermatogenesis in the testis remains far behind that in other epithelia and tissues. The goal of this review is to bridge this gap.

Abstract Src family kinases (SFKs) play a central role in mediating the rapid response of platelets to vascular injury. They transmit activation signals from a diverse repertoire of platelet surface receptors, including the integrin αIIbβ3, the immunoreceptor tyrosine–based activation motif–containing collagen receptor complex GPVI-FcR γ-chain, and the von Willebrand factor receptor complex GPIb-IX-V, which are essential for thrombus growth and stability. Ligand-mediated clustering of these receptors triggers an increase in SFK activity and downstream tyrosine phosphorylation of enzymes, adaptors, and cytoskeletal proteins that collectively propagate the signal and coordinate platelet activation. A growing body of evidence has established that SFKs also contribute to Gq- and Gi-coupled receptor signaling that synergizes with primary activation signals to maximally activate platelets and render them prothrombotic. Interestingly, SFKs concomitantly activate inhibitory pathways that limit platelet activation and thrombus size. In this review, we discuss past discoveries that laid the foundation for this fundamental area of platelet signal transduction, recent progress in our understanding of the distinct and overlapping functions of SFKs in platelets, and new avenues of research into mechanisms of SFK regulation. We also highlight the thrombotic and hemostatic consequences of targeting platelet SFKs.

Abstract Abstract 5263 The Src family kinases (SFKs) play an essential role in collagen- and von Willebrand factor (vWF)-mediated platelet activation. However, the role of SFKs in G protein-coupled receptor (GPCR)-mediated platelet activation is not fully understood, and little is known about the molecular mechanisms by which SFKs are activated by GPCR stimulation. Here we demonstrate that SFKs are activated by the Gq and Gi pathways, respectively and SFKs play important roles in Gq- and Gi-dependent secretion and activation. ADP induced SFK phosphorylation in wild type and Gq−/− platelets, and ADP-induced SFK phosphorylation was inhibited by the P2Y12 antagonist AR-C69931MX or P2Y12 knockout but was not affected by the P2Y1 antagonist MRS-2179. Lyn and Fyn were co-immunoprecipitated with Gi2 in platelets, and ADP-induced SFK phosphorylation was diminished in Lyn−/− platelets. These results demonstrate that ADP induces SFK activation mainly depending on the Gi pathway activated via its receptor P2Y12. Furthermore, epinephrine also dose-dependently induced SFK phosphorylation in mouse platelets. A selective inhibitor of Src family kinase PP2 inhibited ADP-induced Akt phosphorylation, fibrinogen binding, and platelet aggregation. Thus, activation of Gi is sufficient to induce SFK activation, which plays an important role in Gi-dependent platelet activation. We further show that the thrombin receptor PAR4 peptide AYPGKF elicited SFK phosphorylation in P2Y12−/−, but not in Gq−/− platelets, and AYPGKF-induced SFK phosphorylation was inhibited by the calcium chelator dimethyl-BAPTA, suggesting that Gq-dependent SFK phosphorylation is downstream from the Ca2+ signaling. The calcium ionophore, A23187-induced TXA2 synthesis, platelet aggregation and secretion were inhibited by pre-incubation of platelets with PP2. PAR4-induced TXA2 synthesis was also abolished by PP2. Moreover, PAR4-mediated granule secretion, integrin aIIbb3 activation, and aggregation of P2Y12 deficient platelets were partially inhibited by PP2 or a PKC inhibitor Ro-31-8220, but were completely abolished by Ro-31-8220 plus PP2 or dimethyl-BAPTA, suggesting that Ca2+/SFKs and PKC represent two parallel signaling pathways mediating Gq-dependent platelet activation. In summary, SFKs can be activated by Gq/Ca2+-dependent mechanisms and by Gi-dependent mechanisms, and SFKS play important roles in Gq- and Gi-dependent platelet activation. Disclosures: No relevant conflicts of interest to declare.

Abstract Polymorphonuclear leukocyte (PMN)–platelet interactions at sites of vascular damage contribute to local and systemic inflammation. We sought to determine the role of “outside-in” signaling by Src-family tyrosine kinases (SFKs) in the regulation of αMβ2-integrin–dependent PMN recruitment by activated platelets under (patho)physiologic conditions. Activation-dependent epitopes in β2 integrin were exposed at the contact sites between PMNs and platelets and were abolished by SFK inhibitors. PMNs from αMβ2−/−, hck−/−fgr−/−, and hck−/−fgr−/−lyn−/− mice had an impaired capacity to adhere with activated platelets in suspension. Phosphorylation of Pyk2 accompanied PMN adhesion to platelets and was blocked by inhibition as well as by genetic deletion of αMβ2 integrin and SFKs. A Pyk2 inhibitor reduced platelet-PMN adhesion, indicating that Pyk2 may be a downstream effector of SFKs. Analysis of PMN-platelet interactions under flow revealed that SFK signaling was required for αMβ2-mediated shear-resistant adhesion of PMNs to adherent platelets, but was dispensable for P-selectin–PSGL-1–mediated recruitment and rolling. Finally, SFK activity was required to support PMN accumulation along adherent platelets at the site of vascular injury, in vivo. These results definitely establish a role for SFKs in PMN recruitment by activated platelets and suggest novel targets to disrupt the pathophysiologic consequences of platelet-leukocyte interactions in vascular disease.

Malignant mesothelioma (MM) is a deadly tumor mainly caused by exposure to asbestos. Unfortunately, no current treatment is able to change significantly the natural history of the disease, which has a poor prognosis in the majority of patients. The non-receptor tyrosine kinase SRC and other SRC family kinase (SFK) members are frequently hyperactivated in many cancer types, including MM. Several works have indeed suggested that SFKs underlie MM cell proliferation, survival, motility, and invasion, overall affecting multiple oncogenic pathways. Consistently, SFK inhibitors effectively counteracted MM cancerous features at the preclinical level. Dasatinib, a multi-kinase inhibitor targeting SFKs, was also assessed in clinical trials either as second-line treatment for patients with unresectable MM or, more recently, as a neoadjuvant agent in patients with resectable MM. Here, we provide an overview of the molecular mechanisms implicating SFKs in MM progression and discuss possible strategies for a more successful clinical application of SFK inhibitors. Our aim is to stimulate discussion and further consideration of these agents in better designed preclinical and clinical studies to make the most of another class of powerful antitumoral drugs, which too often are lost in translation when applied to MM.

Sperm capacitation is a prerequisite for successful fertilization. Increase in tyrosine phosphorylation is considered the hallmark of capacitation and attempts to understand its regulation are ongoing. In this regard, we attempted to study the role of SRC family kinases (SFKs) in the hamster sperm functions. Interestingly, we found the presence of the lymphocyte-specific protein tyrosine kinase, LCK, in mammalian spermatozoa and further characterized it in terms of its localization and function. LCK was found in spermatozoa of several species, and its transcript was identified in the hamster testis. Autophosphorylation of LCK at the Y394 residue increased as capacitation progressed, indicating an upregulation of LCK activity during capacitation. Inhibition of LCK (and perhaps the other SFKs) with the use of a specific inhibitor showed a significant decrease in protein tyrosine phosphorylation of several proteins, implying LCK/SFKs as key tyrosine kinase(s) regulating tyrosine phosphorylation during hamster sperm capacitation. Dihydrolipoamide dehydrogenase was identified as a substrate for LCK/SFK. LCK/SFKs inhibition significantly reduced the percentage fertilization (in vitro) but had no effect on sperm motility, hyperactivation and acrosome reaction. In summary, this is the first report on the presence of LCK, an SFK of hematopoietic lineage in spermatozoa besides being the first study on the role of SFKs in the spermatozoa of Syrian hamsters.

Protein tyrosine kinases have been recognized as important actors of cell transformation and cancer progression, since their discovery as products of viral oncogenes. SRC-family kinases (SFKs) play crucial roles in normal hematopoiesis. Not surprisingly, they are hyperactivated and are essential for membrane receptor downstream signaling in hematological malignancies such as acute myeloid leukemia (AML) and mastocytosis. The precise roles of SFKs are difficult to delineate due to the number of substrates, the functional redundancy among members, and the use of tools that are not selective. Yet, a large num ber of studies have accumulated evidence to support that SFKs are rational therapeutic targets in AML and mastocytosis. These two pathologies are regulated by two related receptor tyrosine kinases, which are well known in the field of hematology: FLT3 and KIT. FLT3 is one of the most frequently mutated genes in AML, while KIT oncogenic mutations occur in 80–90% of mastocytosis. Studies on oncogenic FLT3 and KIT signaling have shed light on specific roles for members of the SFK family. This review highlights the central roles of SFKs in AML and mastocytosis, and their interconnection with FLT3 and KIT oncoproteins.

The earliest visible indications for the transition to embryos in mammalian eggs, known as egg activation, are cortical granules exocytosis (CGE) and resumption of meiosis (RM); these events are triggered by the fertilizing spermatozoon through a series of Ca2+transients. The pathways, within the egg, leading to the intracellular Ca2+release and to the downstream cellular events, are currently under intensive investigation. The involvement of Src family kinases (SFKs) in Ca2+release at fertilization is well supported in marine invertebrate eggs but not in mammalian eggs. In a previous study we have shown the expression and localization of Fyn, the first SFK member demonstrated in the mammalian egg. The purpose of the current study was to identify other common SFKs and resolve their function during activation of mammalian eggs. All three kinases examined: Fyn, c-Src and c-Yes are distributed throughout the egg cytoplasm. However, Fyn and c-Yes tend to concentrate at the egg cortex, though only Fyn is localized to the spindle as well. The different localizations of the various SFKs imply the possibility of their different functions within the egg. To examine whether SFKs participate in the signal transduction pathways during egg activation, we employed selective inhibitors of the SFKs activity ((PP2 and SU6656). The results demonstrate that RM, which is triggered by Ca2+elevation, is an SFK-dependent process, while CGE, triggered by either Ca2+elevation or protein kinase C (PKC), is not. The possible involvement of SFKs in the signal transduction pathways that lead from the sperm–egg fusion site downstream of the Ca2+release remains unclear.

ABSTRACT The upregulation of Src family kinases (SFKs) has been implicated in cancer progression, but the molecular mechanisms regulating their transforming potentials remain unclear. Here we show that the transforming ability of all SFK members is suppressed by being distributed to the cholesterol-enriched membrane microdomain. All SFKs could induce cell transformation when overexpressed in C-terminal Src kinase (Csk)-deficient fibroblasts. However, their transforming abilities varied depending on their affinity for the microdomain. c-Src and Blk, with a weak affinity for the microdomain due to a single myristate modification at the N terminus, could efficiently induce cell transformation, whereas SFKs with both myristate and palmitate modifications were preferentially distributed to the microdomain and required higher doses of protein expression to induce transformation. In contrast, disruption of the microdomain by depleting cholesterol could induce a robust transformation in Csk-deficient fibroblasts in which only a limited amount of activated SFKs was expressed. Conversely, the addition of cholesterol or recruitment of activated SFKs to the microdomain via a transmembrane adaptor, Cbp/PAG1, efficiently suppressed SFK-induced cell transformation. These findings suggest that the membrane microdomain spatially limits the transforming potential of SFKs by sequestering them away from the transforming pathways.

Dopo l'attivazione, i neutrofili rilasciano fibre extracellulari o trappole extracellulari (NETs), strutture composte da cromatina e proteine granulari che legano e uccidono agenti patogeni. Tuttavia, i NETs possono contribuire a patologie sistemiche o locali, come la sepsi, la vasculite e patologie polmonari croniche come la fibrosi cistica. I meccanismi di trasduzione del segnale che regolano la formazione dei NETs sono poco conosciuti. Infatti, l'unica via finora individuata in grado di indurre la formazione dei NETs è quella basata sul modulo proteina chinasi C / intermedi reattivi dell'ossigeno (ROI). Dato il ruolo importante della famiglia delle Src chinasi (SFKs) nelle patologie infiammatorie, abbiamo studiato se le SFKs e Syk, una tirosin chinasi citoplasmatica posizionata a valle di vie di trasduzione del segnale SFKs-regolate nei leucociti, regolano la formazione dei NETs. A tal fine, i NETs sono stati studiati in neutrofili umani e murini stimolati con diversi agonisti, tra cui il beta-glucano (BG), un componente della parete cellulare del lievito riconosciuto dal recettore Dectin-1 C-type lectin. L’inibitore delle SFKs, PP2, e l'inibitore di Syk, PRT-060318, sono stati utilizzati come farmaci selettivi per la via di segnalazione indotta dal Dectin-1. Qui mostriamo che il beta-glucano è uno stimolo efficace per l'induzione dei NETs, mostrando i suoi effetti anche prima del PMA. Inoltre, in questo lavoro abbiamo dimostrato che i NETs da beta-glucano richiedono sia le SFKs che la produzione di ROS, sebbene non abbiamo identificato quale chinasi delle SFKs sia coinvolta. Diversamente dal BG, il PMA induceva rilascio di NETs in maniera dipendente dalla produzione di ROS, ma non dalle SFKs. I nostri dati evidenziano anche il ruolo di Syk nella formazione dei NETs innescata dal beta-glucano. In conclusione, in questo progetto abbiamo identificato alcuni possibili bersagli farmacologici per modulare la formazione dei NETs ed evitarne il risvolto patologico.
Upon activation, neutrophils release extracellular fibers or neutrophil extracellular traps (NETs), structures composed of chromatin and granule proteins that bind and kill pathogens. However, NETs can contribute to systemic and local pathologies such as sepsis, vasculitis and chronic lung pathologies like cystic fibrosis. Signal transduction mechanisms regulating NET formation are poorly understood. In fact, the only pathway identified so far to be able to induce NET formation is one based on a protein kinase C/reactive oxygen intermediates (ROIs) module. Given the important role of Src kinase family (SFKs) in inflammatory pathologies, we addressed whether SFKs and Syk, a cytoplasmic tyrosine kinase placed downstream SFK-regulated signal transduction pathways in leukocytes regulate NET formation. To this purpose, NETs were examined in human and murine neutrophils stimulated with different agonists, including beta-glucan (BG), a yeast surface component recognized by the C-type lectin receptor Dectin-1. The SFKs inhibitor PP2 and the Syk inhibitor PRT-060318 were used as selective drugs targeting the Dectin-1 triggered signaling pathway. Here we show that beta-glucan is an effective stimulus for the induction of NETs, displaying its effects even earlier than PMA. Additionally, in this work we demonstrate that beta-glucan-induced NETs requires both SFKs and ROS production though we did not identified the SFK involved. Differently from BG, PMA induced NET release in a manner dependent on ROS production but not on SFKs. Our data highlight also the role of Syk in NET formation triggered by beta-glucan. In conclusion, in this project we identified some possible drug targets to modulate NET formation and to avoid the pathogenic side of NETs.