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)

Philadelphia chromosome-positive leukemias result from the fusion of the BCR and ABL genes, which generates a functional chimeric molecule. The Abr protein is very similar to Bcr but lacks a structural domain which may influence its biological regulatory capabilities. Both Abr and Bcr have a GTPase-activating protein (GAP) domain similar to those found in other proteins that stimulate GTP hydrolysis by members of the Rho family of GTP-binding proteins, as well as a region of homology with the guanine nucleotide dissociation-stimulating domain of the DBL oncogene product. We purified as recombinant fusion proteins the GAP- and Dbl-homology domains of both Abr and Bcr. The Dbl-homology domains of Bcr and Abr were active in stimulating GTP binding to CDC42Hs, RhoA, Rac1, and Rac2 (rank order, CDC42Hs > RhoA > Rac1 = Rac2) but were inactive toward Rap1A and Ha-Ras. Both Bcr and Abr acted as GAPs for Rac1, Rac2, and CDC42Hs but were inactive toward RhoA, Rap1A, and Ha-Ras. Each individual domain bound in a noncompetitive manner to GTP-binding protein substrates. These data suggest the multifunctional Bcr and Abr proteins might interact simultaneously and/or sequentially with members of the Rho family to regulate and coordinate cellular signaling.
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PMID:Abr and Bcr are multifunctional regulators of the Rho GTP-binding protein family. 747 68

The integrin family of cell surface receptors mediates cell adhesion to components of the extracellular matrix (ECM). Integrin engagement with the ECM initiates signaling cascades that regulate the organization of the actin-cytoskeleton and changes in gene expression. The Rho subfamily of Ras-related low-molecular-weight GTP-binding proteins and several protein tyrosine kinases have been implicated in mediating various aspects of integrin-dependent alterations in cell homeostasis. Focal adhesion kinase (FAK or pp125FAK) is one of the tyrosine kinases predicted to be a critical component of integrin signaling. To elucidate the mechanisms by which FAK participates in integrin-mediated signaling, we have used expression cloning to identify cDNAs that encode potential FAK-binding proteins. We report here the identification of a cDNA that encodes a new member of the GTPase-activating protein (GAP) family of GTPase regulators. This GAP, termed Graf (for GTPase regulator associated with FAK), binds to the C-terminal domain of FAK in an SH3 domain-dependent manner and preferentially stimulates the GTPase activity of the GTP-binding proteins RhoA and Cdc42. Subcellular localization studies using Graf-transfected chicken embryo cells indicates that Graf colocalizes with actin stress fibers, cortical actin structures, and focal adhesions. Graf mRNA is expressed in a variety of avian tissues and is particularly abundant in embryonic brain and liver. Graf represents the first example of a regulator of the Rho family of small GTP-binding proteins that exhibits binding to a protein tyrosine kinase. We suggest that Graf may function to mediate cross talk between the tyrosine kinases such as FAK and the Rho family GTPase that control steps in integrin-initiated signaling events.
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PMID:An SH3 domain-containing GTPase-activating protein for Rho and Cdc42 associates with focal adhesion kinase. 864 27

The aim of our study was to evaluate the effect of ADP and the role of cytoskeleton reorganization during reversible and irreversible platelet aggregation induced by ADP and thrombin, respectively, on the heterodimeric (p85alpha-p110) phosphoinositide 3-kinase translocation to the cytoskeleton and its activation. Reversible ADP-induced aggregation was accompanied by a reversible reorganization of the cytoskeleton and an increase in levels of the regulatory subunit p85alpha in this cytoskeleton similar to the increase observed in thrombin-activated platelets. This translocation followed a course parallel to the amplitude of aggregation. No increase in levels of both phosphatidylinositol (3, 4)-bisphosphate (PtdIns(3,4)P2) and phosphatidylinositol-(3,4,5)P3 could, however, be detected even at the maximum aggregation and PI 3-kinase alpha translocation. Moreover, in contrast to the situation for thrombin stimulation, the GTP-binding protein RhoA was hardly translocated to the cytoskeleton when platelets were stimulated with ADP, whereas translocation of pp60(c-)src and focal adhesion kinase did occur. These results suggest (i) translocation of signaling enzymes does not necessarily imply their activation, (ii) the reversibility of ADP-induced platelet aggregation may be the cause or the result of a lack of PI 3-kinase activation and hence of PtdIns(3,4)P2 production, and (iii) RhoA does not seem to be involved in the ADP activation pathway of platelets. Whether PtdIns(3,4)P2 or RhoA may contribute to the stabilization of platelet aggregates remains to be established.
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PMID:Reversible translocation of phosphoinositide 3-kinase to the cytoskeleton of ADP-aggregated human platelets occurs independently of Rho A and without synthesis of phosphatidylinositol (3,4)-bisphosphate. 903 May 42

The small GTPase RhoA plays a critical role in signaling pathways activated by serum-derived factors, such as lysophosphatidic acid (LPA), including the formation of stress fibers in fibroblasts and neurite retraction and rounding of soma in neuronal cells. Previously, we have shown that ectopic expression of v-Crk, an SH2/SH3 domain-containing adapter proteins, in PC12 cells potentiates nerve growth factor (NGF)-induced neurite outgrowth and promotes the survival of cells when NGF is withdrawn. In the present study we show that, when cultured in 15% serum or lysophosphatidic acid-containing medium, the majority of v-Crk-expressing PC12 cells (v-CrkPC12 cells) display a flattened phenotype with broad lamellipodia and are refractory to NGF-induced neurite outgrowth unless serum is withdrawn. v-Crk-mediated cell flattening is inhibited by treatment of cells with C3 toxin or by mutation in the Crk SH2 or SH3 domain. Transient cotransfection of 293T cells with expression plasmids for p160ROCK (Rho-associated coiled-coil-containing kinase) and v-Crk, but not SH2 or SH3 mutants of v-Crk, results in hyperactivation of p160ROCK. Moreover, the level of phosphatidylinositol-4,5-bisphosphate is increased in v-CrkPC12 cells compared to the levels in mutant v-Crk-expressing cells or wild-type cells, consistent with PI(4)P5 kinase being a downstream target for Rho. Expression of v-Crk in PC12 cells does not result in activation of Rac- or Cdc42-dependent kinases PAK and S6 kinase, demonstrating specificity for Rho. In contrast to native PC12 cells, in which focal adhesions and actin stress fibers are not observed, immunohistochemical analysis of v-CrkPC12 cells reveals focal adhesion complexes which are formed at the periphery of the cell and are connected to actin cables. The formation of focal adhesions correlates with a concomitant upregulation in the expression of focal adhesion proteins FAK, paxillin, alpha3-integrin, and a higher-molecular-weight form of beta1-integrin. Our results indicate that v-Crk activates the Rho-signaling pathway and serves as a scaffolding protein during the assembly of focal adhesions in PC12 cells.
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PMID:Activation of Rho-dependent cell spreading and focal adhesion biogenesis by the v-Crk adaptor protein. 956 23

In preadipocytes, alpha2-adrenergic receptor (alpha2-AR) stimulation leads to a Gi/Go-dependent rearrangement of actin cytoskeleton. This is characterized by a rapid cell spreading, the formation of actin stress fibers, and the increase in tyrosyl phosphorylation of the focal adhesion kinase (pp125(FAK)). These cellular events being tightly controlled by the small GTPase p21(rhoA), the existence of a Gi/Go-dependent coupling of alpha2-AR to p21(rhoA) in preadipocytes was proposed. In alpha2AF2 preadipocytes (a cell clone derived from the 3T3F442A preadipose cell line and which stably expresses the human alpha2C10-adrenergic receptor) alpha2-adrenergic-dependent induction of cell spreading, formation of actin stress fibers, and increase in tyrosyl phosphorylation of pp125(FAK) were abolished by pretreatment of the preadipocytes with the C3 exoenzyme, a toxin which impairs p21(rhoA) activity by ADP-ribosylation. Conversely, C3 exoenzyme had no effect on the alpha2-adrenergic-dependent increase in tyrosyl phosphorylation and shift of ERK2 mitogen-activated protein kinase. alpha2-Adrenergic stimulation also led to an increase in GDP/GTP exchange on p21(rhoA), as well as to an increase in the amount of p21(rhoA) in the particulate fraction of alpha2AF2 preadipocytes. Stable transfection of alpha2AF2 preadipocytes with the COOH-terminal domain of betaARK1 (betaARK-CT) (a blocker of Gbeta gamma-action), strongly inhibited the alpha2-adrenergic-dependent increase in tyrosyl phos- phorylation and shift of ERK2, without modification of the tyrosyl phosphorylation of pp125(FAK) and spreading of preadipocytes. These results show that alpha2-adrenergic-dependent reorganization of actin cytoskeleton requires the activation of p21(rhoA) in preadipocytes. Conversely to the activation of the p21(ras)/mitogen-activated protein kinase pathway, the alpha2-adrenergic activation of p21(rhoA)-dependent pathways are independent of the beta gamma-subunits of heterotrimeric G proteins.
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PMID:Gbeta gamma-independent coupling of alpha2-adrenergic receptor to p21(rhoA) in preadipocytes. 962 80

The interaction of cells with their substrate triggers cascades of signal transduction that result in profound changes in cell morphology. The nature of these signals and how they are integrated to orchestrate changes in cell shape are beginning to be elucidated. In particular, adhesive interactions between cells and their substrate, mediated by cell-surface integrins and extracellular matrix (ECM) proteins, appear to result in massive rearrangement of the cell cytoskeleton via the small G-protein, Rho. Here we show that in mouse fibroblasts, the interaction between cells and their substrate results in the rapid recruitment to the cytoskeleton of RasGAP (p120RasGAP), its associated protein of 190 kilodaltons, the GTPase activating protein for RhoA (p190RhoGAP) and the focal adhesion kinase (p125FAK). Similar results were obtained when cells were plated on ECM proteins, such as fibronectin, suggesting that the phenomenon is integrin mediated. These studies suggest that in fibroblasts, cell-substrate interaction triggered by integrin engagement result in the recruitment to the cytoskeleton of signaling molecules such as p120RasGAP, p190RhoGAP and p125FAK and may be involved in the formation of membrane cytoskeleton-associated signaling complexes that are important in cytoarchitectural reorganization.
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PMID:Rapid recruitment of p120RasGAP and its associated protein, p190RhoGAP, to the cytoskeleton during integrin mediated cell-substrate interaction. 969 May 9

The ubiquitously expressed Na-H exchanger NHE1 functions in regulating intracellular pH and cell volume. NHE1 activity is stimulated by hormones, growth factors, and activation of integrin receptors. We recently determined that NHE1 activity is also stimulated by activation of the low molecular weight GTPase RhoA and that increases in NHE1 activity are necessary for RhoA-induced formation of actin stress fibers. We now show that NHE1 acts downstream of RhoA to modulate initial steps in integrin signaling for the assembly of focal adhesions. Adhesion of CCL39 fibroblasts on fibronectin was markedly delayed in the presence of the NHE inhibitor ethylisopropylamiloride. In mutant PS120 cells, derived from CCL39 fibroblasts but lacking NHE1, adhesion was also delayed but was rescued in PS120 cells stably expressing NHE1. In the absence of NHE1 activity, cell spreading was inhibited, and the accumulation of integrins, paxillin, and vinculin at focal contacts was impaired. Additionally, tyrosine phosphorylation of p125(FAK) induced by integrin clustering was also impaired. Inactivation of RhoA with C3 transferase and inhibition of the Rho-kinase p160ROCK with the pyridine derivative Y-27632 completely abolished activation of NHE1 by integrins but not by platelet-derived growth factor. These findings indicate that NHE1 acts downstream of RhoA to contribute a previously unrecognized critical signal to proximal events in integrin-induced cytoskeletal reorganization.
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PMID:Na-H exchange acts downstream of RhoA to regulate integrin-induced cell adhesion and spreading. 969 82

We have shown that nonvoltage-operated Ca(2+) entry regulates human umbilical vein endothelial cell adhesion, migration, and proliferation on type IV collagen. We now demonstrate a requirement for Ca(2+) influx for activation of the RhoA pathway during endothelial cell spreading on type IV collagen. Reorganization of actin into stress fibers was complete when the cells where fully spread at 90 minutes. No actin organization into stress fibers was seen in endothelial cells plated on type I collagen, indicating a permissive effect of type IV collagen. CAI, a blocker of nonvoltage-operated Ca(2+) channels, prevented development of stress fiber formation in endothelial cells on type IV collagen. This permissive effect was augmented by Ca(2+) influx, as stimulated by 0. 5 microM thapsigargin or 0.1 microM ionomycin, yielding faster development of actin stress fibers. Ca(2+) influx and actin rearrangement in response to thapsigargin and ionomycin were abrogated by CAI. Activated, membrane-bound RhoA is a substrate for C3 exoenzyme which ADP-ribosylates and inactivates RhoA, preventing actin stress fiber formation. Pretreatment of endothelial cells with C3 exoenzyme prevented basal and thapsigargin-augmented stress fiber formation. While regulation of Ca(2+) influx did not alter RhoA translocation, it reduced in vitro ADP-ribosylation of RhoA (P(2)<0. 05), suggesting Ca(2+) influx is needed for RhoA activation during spreading on type IV collagen; no Ca(2+) regulated change in RhoA was seen in HUVECs spreading on type I collagen matrix. Blockade of Ca(2+) influx of HUVEC spread on type IV collagen also reduced tyrosine phosphorylation of p190Rho-GAP and blocked thapsigargin-enhanced binding of p190Rho-GAP to focal adhesion kinase. Thus, Ca(2+) influx is necessary for RhoA activation and for linkage of the RhoA/stress fiber cascade to the focal adhesion/focal adhesion kinase pathway during human umbilical vein endothelial cell spreading on type IV collagen.
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PMID:Regulation of the RhoA pathway in human endothelial cell spreading on type IV collagen: role of calcium influx. 1050 26

The modulation of endothelial barrier function is thought to be a function of contractile tension mediated by the cell cytoskeleton, which consists of actomyosin stress fibers (SF) linked to focal adhesions (FA). We tested this hypothesis by dissociating SF/FA with Clostridium botulinum exoenzyme C3 transferase (C3), an inhibitor of the small GTP-binding protein RhoA. Bovine pulmonary artery endothelial cell (EC) monolayers given C3, C3 + thrombin, thrombin, or no treatment were examined using a size-selective permeability assay and quantitative digital imaging measurements of SF/FA. C3 treatment disassembled SF/FA, stimulated diffuse myosin II immunostaining, and reduced the phosphotyrosine (PY) content of paxillin and 130- to 140-kDa proteins that included p125(FAK). C3-treated monolayers displayed a 60-85% decline in F-actin content and a 170-300% increase in EC surface area with enhanced endothelial barrier function. This activity correlated with reorganization of F-actin and PY protein(s) to beta-catenin-containing cell-cell junctions. Because C3 prevented the thrombin-induced formation of myosin ribbons, SF/FA, and the increased PY content of proteins, these characteristics were Rho dependent. Our data show that C3 inhibition of Rho proteins leads to cAMP-like characteristics of reduced SF/FA and enhanced endothelial barrier function.
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PMID:RhoA inactivation enhances endothelial barrier function. 1056 88

The Tec family is a recently emerging subfamily of non-receptor protein-tyrosine kinases (PTKs) represented by its first member, Tec. This family is composed of five members, namely Tec, Btk. Itk/Emt/Tsk, Bmx and Txk/Rlk. The most characteristic feature of this family is the presence of a pleckstrin homology (PH) domain in their protein structure. The PH domain is known to bind phosphoinositides; on this basis, Tec family PTKs may act as merge points of phosphotyrosine-mediated and phospholipid-mediated signaling systems. Many Tec family proteins are abundantly expressed in hematopoietic tissues, and are presumed to play important roles in the growth and differentiation processes of blood cells. Supporting this, mutations in the Btk gene cause X chromosome-linked agammaglobulinemia (XLA) in humans and X chromosome-linked immunodeficiency (Xid) in mice, indicating that Btk activity is indispensable for B-cell ontogeny. In addition, Tec family kinases have been shown to be involved in the intracellular signaling mechanisms of cytokine receptors, lymphocyte surface antigens, heterotrimeric G-protein-coupled receptors and integrin molecules. Efforts are being made to identify molecules which interact with Tec kinases to transfer Tec-mediated signals in vivo. Candidates for such second messengers include PLC-gamma2, guanine nucleotide exchange factors for RhoA and TFII-I/BAP-135. This review summarizes current knowledge concerning the input and output factors affecting the Tec kinases.
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PMID:Tec family of protein-tyrosine kinases: an overview of their structure and function. 1064 81


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