Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.10.2 (focal adhesion kinase)
44,029 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous studies using cytochalasins and latrunculin B, inhibitors of actin polymerization, showed that filamentous (F)-actin had a negative regulatory role in Fc epsilon receptor I (Fc epsilon RI) signaling. How F-actin is involved in regulating the activation of mast cells is unknown. In this study we investigated the role of F-actin in mast cell activation induced by aggregation of the glycosylphosphatidylinositol (GPI)-anchored proteins Thy-1 and TEC-21, and compared it to activation via Fc epsilon RI. Pretreatment of rat basophilic leukemia cells with latrunculin B inhibited the Thy-1-induced actin polymerization and elevated the Thy-1-mediated secretory and calcium responses. Inhibition of actin polymerization followed by Thy-1 aggregation resulted in an increased tyrosine phosphorylation of Syk, phospholipase C gamma (PLC gamma), Gab2 and linker for activation of T cells (LAT) adapters, and some other signaling molecules. Enzymatic activities of phosphatidylinositol 3-kinase, PLC gamma, and phosphatase SHP-2 were also up-regulated, but tyrosine phosphorylation of ezrin was inhibited. Similar changes were observed in Fc epsilon RI-activated cells. Significant changes in intracellular distribution, tyrosine phosphorylation, and/or enzymatic activities of signaling molecules occurred in latrunculin-pretreated cells before cell triggering. The combined data suggest that actin polymerization is critical for setting the thresholds for mast cell signaling via aggregation of both Fc epsilon RI and GPI-anchored proteins.
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PMID:Involvement of filamentous actin in setting the threshold for degranulation in mast cells. 1516 32

Shiga toxin is a bacterial toxin consisting of A and B subunits. Generally, the essential cytotoxicity of the toxin is thought to be mediated by the A subunit, which possesses RNA cleavage activity and thus induces protein synthesis inhibition. We previously reported, however, that the binding of the Shiga toxin 1-B subunit to globotriaosyl ceramide, a functional receptor for Shiga toxin, induces intracellular signals in a manner that is dependent on glycolipid-enriched membrane domains, or lipid rafts. Although the precise role of this signaling mechanism is not known, here we report that Shiga-toxin-mediated intracellular signals induce cytoskeleton remodeling in ACHN cells derived from renal tubular epithelial carcinoma. Using confocal laser scanning microscopy, we observed that Shiga toxin 1-B treatment induces morphological changes in ACHN cells in a time-dependent manner. In addition, the morphological changes were accompanied by the redistribution of a number of proteins, including actin, ezrin, CD44, vimentin, cytokeratin, paxillin, FAK, and alpha- and gamma-tubulins, all of which are involved in cytoskeletal organization. The transient phosphorylation of ezrin and paxillin was also observed during the course of protein redistribution. Experiments using inhibitors for a variety of kinases suggested the involvement of lipid rafts, Src family protein kinase, PI 3-kinase, and RHO-associated kinase in Shiga toxin 1-B-induced ezrin phosphorylation. Shiga toxin 1-B-induced cytoskeletal remodeling should provide an in vitro model that can be used to increase our understanding of the pathogenesis of Shiga-toxin-mediated cell injury and the role of lipid-raft-mediated cell signaling in cytoskeletal remodeling.
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PMID:Shiga toxin binding to globotriaosyl ceramide induces intracellular signals that mediate cytoskeleton remodeling in human renal carcinoma-derived cells. 1526 87

In addition to providing a regulated linkage between the membrane and the actin cytoskeleton, ezrin participates in signal transduction pathways. Here we describe that expression of the ezrin Y145F mutant delays epithelial cell spreading on fibronectin by inhibiting events leading to FAK activation. The defect in spreading was rescued by the overexpression of catalytically functional Src. We demonstrate that ezrin Y145 is phosphorylated in A431 cells stimulated with epidermal growth factor (EGF) and in v-Src-transformed cells. Moreover in cells devoid of Src, SYF-/- fibroblasts, ezrin Y145 phosphorylation could only be detected upon the introduction of an active form of Src. The phosphorylation of ezrin at Y145 required prior binding of the Src SH2 domain to ezrin. Our results further show that Src activity influences its binding to ezrin and a positive feedback mechanism for Src-mediated Y145 phosphorylation is implied. Interestingly, cells expressing ezrin Y145F did not proliferate when cultured in a 3D collagen gel. Collectively, our results demonstrate a key signaling input of Src-dependent ezrin phosphorylation in adhesion-mediated events in epithelial cells.
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PMID:Src-dependent ezrin phosphorylation in adhesion-mediated signaling. 1564 76

CD44 is involved in leukocyte migration and activation and has recently been reported to contribute to leukocyte extravasation by associating with CD49d. We explored whether similar changes in CD44 activity are seen in vivo using murine alopecia areata (AA) as a chronic, organ-related autoimmune disease model system. Expression of the activated, hyaluronan-binding form of CD44, and of CD49d, was elevated in draining lymph node cells (LNC) of AA-affected mice as compared to control mice. LNC of AA mice displayed increased motility, proliferative activity and apoptosis resistance, which were equally well inhibited by anti-CD44 and anti-CD49d. The latter is the sequelae of the association between CD44 and CD49d that is seen in activated lymphocytes. Significantly, due to CD44-CD49d complex formation, CD44 gains access to focal adhesion kinase and CD49d gains access to CD44-associated lck and ezrin, such that downstream kinases become activated via CD44 or CD49d engagement. Thus, by their association, CD44 and CD49d mutually avail themselves of the partner's signaling pathways and the ligand binding of each one triggers signaling pathways of both. This strongly influences the lymphocytes' activation state and function.
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PMID:In vivo CD44-CD49d complex formation in autoimmune disease has consequences on T cell activation and apoptosis resistance. 1703 68

Understanding the precise molecular mechanisms that trigger liver cancer cell migration and invasion could develop novel therapeutic strategies targeting cancer cell invasion to increase the sensitivity to current treatment modalities. In the current study, 49 patients with hepatocellular carcinoma (HCC) were included prospectively. Liver tumour and adjacent non-tumour tissues were detected for the expression of Proline-rich tyrosine kinase 2 (Pyk2), focal adhesion kinase (FAK), ezrin and fibronectin at protein and/or gene levels. Correlation between the expressions of Pyk2/FAK with the clinical pathological data was analysed. Protein expression of Pyk2 was also examined in a nude mice orthotopic liver tumour model with higher metastatic potential. There were 59% (29 out of 49) and 57% (28 out of 49) of HCC patients with higher levels of Pyk2 and FAK protein/gene expression, respectively. We observed a positive correlation between the protein and gene expression levels of Pyk2 and FAK (P=0.000, r=0.875). Overexpression of Pyk2 and FAK was significantly correlated with shorter disease-free survival. Patients with higher levels of Pyk2/FAK had larger tumour size and advanced Edmonson grading. In the animal studies, Pyk2 overexpression was found in infiltrative tumour cells and lung metastatic nodules. In conclusion, overexpression of Pyk2 and FAK was found in nearly 60% of HCC patients and was significantly correlated with poor prognosis. The significance of Pyk2 in HCC invasiveness was confirmed by animal studies.
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PMID:The significance of proline-rich tyrosine kinase2 (Pyk2) on hepatocellular carcinoma progression and recurrence. 1755 99

Hyperosmotic shrinkage induces multiple cellular responses, including activation of volume-regulatory ion transport, cytoskeletal reorganization, and cell death. Here we investigated the possible roles of ezrin/radixin/moesin (ERM) proteins in these events. Osmotic shrinkage of Ehrlich Lettre ascites cells elicited the formation of long microvillus-like protrusions, rapid translocation of endogenous ERM proteins and green fluorescent protein-tagged ezrin to the cortical region including these protrusions, and Thr(567/564/558) (ezrin/radixin/moesin) phosphorylation of cortical ERM proteins. Reduced cell volume appeared to be the critical parameter in hypertonicity-induced ERM protein activation, whereas alterations in extracellular ionic strength or intracellular pH were not involved. A shrinkage-induced increase in the level of membrane-associated phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P(2)] appeared to play an important role in ERM protein activation, which was prevented after PtdIns(4,5)P(2) depletion by expression of the synaptojanin-2 phosphatase domain. While expression of constitutively active RhoA increased basal ERM phosphorylation, the Rho-Rho kinase pathway did not appear to be involved in shrinkage-induced ERM protein phosphorylation, which was also unaffected by the inhibition or absence of Na(+)/H(+) exchanger isoform (NHE1). Ezrin knockdown by small interfering RNA increased shrinkage-induced NHE1 activity, reduced basal and shrinkage-induced Rho activity, and attenuated the shrinkage-induced formation of microvillus-like protrusions. Hyperosmolarity-induced cell death was unaltered by ezrin knockdown or after phosphatidylinositol 3-kinase (PI3K) inhibition. In conclusion, ERM proteins are activated by osmotic shrinkage in a PtdIns(4,5)P(2)-dependent, NHE1-independent manner. This in turn mitigates the shrinkage-induced activation of NHE1, augments Rho activity, and may also contribute to F-actin rearrangement. In contrast, no evidence was found for the involvement of an NHE1-ezrin-PI3K-PKB pathway in counteracting shrinkage-induced cell death.
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PMID:Osmotic cell shrinkage activates ezrin/radixin/moesin (ERM) proteins: activation mechanisms and physiological implications. 1797 45

CAKbeta (cell adhesion kinase beta)/PYK2 (proline-rich tyrosine kinase 2) is the second protein-tyrosine kinase of the FAK (focal adhesion kinase) subfamily. It is different from FAK in that it is activated following an increase in cytoplasmic free Ca2+. In the present study we have investigated how Ca2+ activates CAKbeta/PYK2. Calmodulin-agarose bound CAKbeta/PYK2, but not FAK, in the presence of CaCl2. An alpha-helix (F2-alpha2) present in the FERM (band four-point-one, ezrin, radixin, moesin homology) F2 subdomain of CAKbeta/PYK2 was the binding site of Ca2+/calmodulin; a mutant of this region, L176A/Q177A (LQ/AA) CAKbeta/PYK2, bound to Ca2+/calmodulin much less than the wild-type. CAKbeta/PYK2 is known to be prominently tyrosine phosphorylated when overexpressed from cDNA. The enhanced tyrosine phosphorylation was inhibited by W7, an inhibitor of calmodulin, and by a cell-permeable Ca2+ chelator and was almost defective in the LQ/AA-mutant CAKbeta/PYK2. CAKbeta/PYK2 formed a homodimer on binding of Ca2+/calmodulin, which might then induce a conformational change of the kinase, resulting in transphosphorylation within the dimer. The dimer was formed at a free-Ca2+ concentration of 8-12 muM and was stable at 500 nM Ca2+, but dissociated to a monomer in a Ca2+-free buffer. The dimer formation of CAKbeta/PYK2 FERM domain was partially defective in the LQ/AA-mutant FERM domain and was blocked by W7 and by a synthetic peptide with amino acids 168-188 of CAKbeta/PYK2, but not by a peptide with its LQ/AA-mutant sequence. It is known that the F2-alpha2 helix is found immediately adjacent to a hydrophobic pocket in the FERM F2 lobe, which locks, in the autoinhibited FAK, the C-lobe of the kinase domain. Our results indicate that Ca2+/calmodulin binding to the FERM F2-alpha2 helix of CAKbeta/PYK2 releases its kinase domain from autoinhibition by forming a dimer.
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PMID:Protein-tyrosine kinase CAKbeta/PYK2 is activated by binding Ca2+/calmodulin to FERM F2 alpha2 helix and thus forming its dimer. 1803 Dec 86

Pyk2 (proline-rich tyrosine kinase 2) and FAK (focal adhesion kinase) are highly related tyrosine kinases. One distinguishing feature is the differential regulation of the two enzymes in response to elevation of cytoplasmic calcium. In the latest issue of the Biochemical Journal, Sasaki and co-workers have provided insight into the calcium-dependent regulation of Pyk2. The findings suggest that calmodulin may bind the FERM (4.1/ezrin/radixin/moesin) domain to promote Pyk2 activation in response to calcium signals triggered by vasopressin. While the molecular details of the protein-protein interaction and mechanism of activation remain to be firmly established, this study is the first to provide mechanistic insight into the regulation of Pyk2 by calcium.
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PMID:Calcium-dependent Pyk2 activation: a role for calmodulin? 1829 Jul 63

The highly homologous proteins ezrin, radixin, and moesin link proteins to the actin cytoskeleton. The two family members expressed in T cells, ezrin and moesin, are implicated in promoting T cell activation and polarity. To elucidate the contributions of ezrin and moesin, we conducted a systematic analysis of their function during T cell activation. In response to TCR engagement, ezrin and moesin were phosphorylated in parallel at the regulatory threonine, and both proteins ultimately localized to the distal pole complex (DPC). However, ezrin exhibited unique behaviors, including tyrosine phosphorylation and transient localization to the immunological synapse before movement to the DPC. To ask whether these differences reflect unique requirements for ezrin vs moesin in T cell signaling, we generated mice with conditional deletion of ezrin in mature T cells. Ezrin-/- T cells exhibited normal immunological synapse organization based upon localization of protein kinase C-theta, talin, and phospho-ZAP70. DPC localization of CD43 and RhoGDP dissociation inhibitor, as well as the novel DPC protein Src homology region 2 domain-containing phosphatase-1, was also unaffected. However, recruitment of three novel DPC proteins, ezrin binding protein of 50 kDa, Csk binding protein, and the p85 subunit of PI3K was partially perturbed. Biochemical analysis of ezrin-/- T cells or T cells suppressed for moesin using small interfering RNA showed intact early TCR signaling, but diminished levels of IL-2. The defects in IL-2 production were more pronounced in T cells deficient for both ezrin and moesin. These cells also exhibited diminished phospholipase C-gamma1 phosphorylation and calcium flux. We conclude that despite their unique movement and phosphorylation patterns, ezrin and moesin function together to promote T cell activation.
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PMID:Ezrin and moesin function together to promote T cell activation. 1912 45

JAK2 (Janus tyrosine kinase 2) is important for signalling through many cytokine receptors, and a gain-of-function JAK2 mutation in its pseudokinase domain, V617F, has been implicated in Philadelphia chromosome-negative myeloproliferative neoplasms. How this mutation hyperactivates JAK2 is poorly understood. In the present paper we report our findings that the V617F mutation has little effect on the Vmax of JAK2 kinase activity, but lowers the Km value for substrates. Therefore under physiological conditions where the concentration level of substrates is presumably below saturation, JAK2(V617F) exhibits hyperactivation compared with wild-type JAK2. This lower Km of JAK2(V617F) towards substrates requires the JAK2 FERM (4.1/ezrin/radixin/moesin) domain, as deletion of the FERM domain abolished this effect. We also show that, in contrast with its positive role in JAK2(V617F) hyperactivation, the FERM domain in wild-type JAK2 is inhibitory. Deletion or mutations of the FERM domain resulted in increased basal JAK2 kinase activity. The results of the present study provide the biochemical basis for how V617F hyperactivates JAK2, and identifies novel regulating roles of the JAK2 FERM domain to control kinase activity at different activation states.
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PMID:A regulating role of the JAK2 FERM domain in hyperactivation of JAK2(V617F). 1992 56


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