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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This work investigated the role of Ca2+ mobilization and heterotrimeric G protein activation in mediating angiotensin II-dependent tyrosine phosphorylation signaling patterns. We demonstrate that the predominant, angiotensin II-dependent, tyrosine phosphorylation signaling patterns seen in vascular smooth muscle cells are blocked by the intracellular Ca2+ chelator BAPTA-AM, but not by the Ca2+ channel blocker verapamil. Activation of heterotrimeric G proteins with NaF resulted in a divergent signaling effect; NaF treatment was sufficient to increase tyrosine phosphorylation levels of some proteins independent of angiotensin II treatment. In the same cells, NaF alone had no effect on other cellular proteins, but greatly potentiated the ability of angiotensin II to increase the tyrosine phosphorylation levels of these proteins. Two proteins identified in these studies were paxillin and Jak2. We found that NaF treatment alone, independent of angiotensin II stimulation, was sufficient to increase the tyrosine phosphorylation levels of paxillin. Furthermore, the ability of either NaF and/or angiotensin II to increase tyrosine phosphorylation levels of paxillin is critically dependent on intracellular Ca2+. In contrast, angiotensin II-mediated Jak2 tyrosine phosphorylation was independent of intracellular Ca2+ mobilization and extracellular Ca2+ entry. Thus, our data suggest that angiotensin II-dependent tyrosine phosphorylation signaling cascades are mediated through a diverse set of signaling pathways that are partially dependent on Ca2+ mobilization and heterotrimeric G protein activation.
Mol Cell Biochem 2000 Sep
PMID:The role of Ca2+ mobilization and heterotrimeric G protein activation in mediating tyrosine phosphorylation signaling patterns in vascular smooth muscle cells. 1110 40

Adenosine and/or homocysteine causes endothelial cell apoptosis, a mechanism requiring protein tyrosine phosphatase (PTPase) activity. We investigated the role of focal adhesion contact disruption in adenosine-homocysteine endothelial cell apoptosis. Analysis of focal adhesion kinase (FAK), paxillin, and vinculin demonstrated disruption of focal adhesion complexes after 4 h of treatment with adenosine-homocysteine followed by caspase-induced proteolysis of FAK, paxillin, and p130(CAS). No significant changes were noted in tyrosine phosphorylation of FAK or paxillin. Pretreatment with the caspase inhibitor Z-Val-Ala-Asp-fluoromethylketone prevented adenosine-homocysteine-induced DNA fragmentation and FAK, paxillin, and p130(CAS) proteolysis. Asp-Glu-Val-Asp-ase activity was detectable in endothelial cells after 4 h of treatment with adenosine-homocysteine. The PTPase inhibitor sodium orthovanadate did not prevent endothelial cell retraction or FAK, paxillin, or vinculin redistribution. Sodium orthovanadate did block adenosine-homocysteine-induced FAK, paxillin, and p130(CAS) proteolysis and Asp-Glu-Val-Asp-ase activity. Thus disruption of focal adhesion contacts and caspase-induced degradation of focal adhesion contact proteins occurs in adenosine-homocysteine endothelial cell apoptosis. Focal adhesion contact disruption induced by adenosine-homocysteine is independent of PTPase or caspase activation. These studies demonstrate that disruption of focal adhesion contacts is an early, but not an irrevocable, event in endothelial cell apoptosis.
Am J Physiol Lung Cell Mol Physiol 2001 Feb
PMID:Protein tyrosine phosphatase-dependent proteolysis of focal adhesion complexes in endothelial cell apoptosis. 1115 14

Integrin alpha 3A cytoplasmic tail phosphorylation was mapped to amino acid S1042, as determined by mass spectrometry, and confirmed by mutagenesis. This residue occurs within a "QPSXXE" motif conserved in multiple alpha chains (alpha 3A, alpha 6A, alpha 7A), from multiple species. Phosphorylation of alpha 3A and alpha 6A did not appear to be directly mediated by protein kinase C (PKC) alpha, beta, gamma, delta, epsilon, zeta, or mu, or by any of several other known serine kinases, although PKC has an indirect role in promoting phosphorylation. A S1042A mutation did not affect alpha 3-Chinese hamster ovary (CHO) cell adhesion to laminin-5, but did alter 1) alpha 3-dependent tyrosine phosphorylation of focal adhesion kinase and paxillin (in the presence or absence of phorbol 12-myristate 13 acetate stimulation), and p130(CAS) (in the absence of phorbol 12-myristate 13 acetate stimulation), 2) the shape of cells spread on laminin-5, and 3) alpha 3-dependent random CHO cell migration on laminin-5. In addition, S1042A mutation altered the PKC-dependent, ligand-dependent subcellular distribution of alpha 3 and F-actin in CHO cells. Together, the results demonstrate clearly that alpha 3A phosphorylation is functionally relevant. In addition, the results strongly suggest that alpha 3 phosphorylation may regulate alpha 3 integrin interaction with the cytoskeleton.
Mol Biol Cell 2001 Feb
PMID:Phosphorylation of a conserved integrin alpha 3 QPSXXE motif regulates signaling, motility, and cytoskeletal engagement. 1117 20

Removal of colony-stimulating factor 1 (CSF-1) causes macrophages to round up and to increase their expression of protein tyrosine phosphatase phi (PTP phi). This is accompanied by the disruption of focal complexes and the formation of ruffles. Here we have overexpressed wild-type (WT) PTP phi and a phosphatase-inactive (C325S) mutant in a macrophage cell line in the presence and absence of CSF-1. In the presence of CSF-1, WT PTP phi induces cell rounding and ruffle formation, while C325S PTP phi has no effect. In contrast, in CSF-1-starved cells, C325S PTP phi behaves in a dominant negative fashion, preventing rounding and ruffling. Furthermore, C325S PTP phi increases adhesion in cycling cells, while WT PTP phi enhances motility. In WT PTP phi-overexpressing cells, the focal contact protein paxillin is selectively depleted from focal complexes and specifically dephosphorylated on tyrosine. In contrast, paxillin is hyperphosphorylated in C325S PTP phi-expressing cells. Moreover, a complex containing PTP phi, paxillin, and a paxillin-associated tyrosine kinase, Pyk2, can be immunoprecipitated from macrophage lysates, and the catalytic domain of PTP phi selectively binds paxillin and Pyk2 in vitro. Although PTP phi and Pyk2 do not colocalize with paxillin in focal complexes, all three proteins are colocalized in dorsal ruffles. The results suggest that paxillin is dephosphorylated by PTP phi in dorsal ruffles, using Pyk2 as a bridging molecule, resulting in a reduced pool of tyrosine-phosphorylated paxillin available for incorporation into focal complexes, thereby mediating CSF-1 regulation of macrophage morphology, adhesion, and motility.
Mol Cell Biol 2001 Mar
PMID:Protein tyrosine phosphatase phi regulates paxillin tyrosine phosphorylation and mediates colony-stimulating factor 1-induced morphological changes in macrophages. 1123 16

Paxillin acts as an adaptor protein in integrin signaling. We have shown that paxillin exists in a relatively large cytoplasmic pool, including perinuclear areas, in addition to focal complexes formed at the cell periphery and focal adhesions formed underneath the cell. Several ADP-ribosylation factor (ARF) GTPase-activating proteins (GAPs; ARFGAPs) have been shown to associate with paxillin. We report here that Git2-short/KIAA0148 exhibits properties of a paxillin-associated ARFGAP and appears to be colocalized with paxillin, primarily at perinuclear areas. A fraction of Git2-short was also localized to actin-rich structures at the cell periphery. Unlike paxillin, however, Git2-short did not accumulate at focal adhesions underneath the cell. Git2-short is a short isoform of Git2, which is highly homologous to p95PKL, another paxillin-binding protein, and showed a weaker binding affinity toward paxillin than that of Git2. The ARFGAP activities of Git2 and Git2-short have been previously demonstrated in vitro, and we provided evidence that at least one ARF isoform, ARF1, is an intracellular substrate for the GAP activity of Git2-short. We also showed that Git2-short could antagonize several known ARF1-mediated phenotypes: overexpression of Git2-short, but not its GAP-inactive mutant, caused the redistribution of Golgi protein beta-COP and reduced the amounts of paxillin-containing focal adhesions and actin stress fibers. Perinuclear localization of paxillin, which was sensitive to ARF inactivation, was also affected by Git2-short overexpression. On the other hand, paxillin localization to focal complexes at the cell periphery was unaffected or even augmented by Git2-short overexpression. Therefore, an ARFGAP protein weakly interacting with paxillin, Git2-short, exhibits pleiotropic functions involving the regulation of Golgi organization, actin cytoskeletal organization, and subcellular localization of paxillin, all of which need to be coordinately regulated during integrin-mediated cell adhesion and intracellular signaling.
Mol Biol Cell 2001 Mar
PMID:An ADP-ribosylation factor GTPase-activating protein Git2-short/KIAA0148 is involved in subcellular localization of paxillin and actin cytoskeletal organization. 1125 Oct 77

Nitric oxide (NO) possesses potent anti-inflammatory properties; however, an over-production of NO will promote inflammation and induce cell and tissue dysfunction. Thus, the ability to precisely regulate NO production could prove beneficial in controlling damage. In this study, advantage was taken of the well characterized inflammatory response caused by an intestinal parasite, Trichinella spiralis, to study the relationship between intestinal inflammation and the regulation of nitric oxide synthase-type 2 (NOS-2) expression. Our study revealed that a specific gut inflammatory reaction results in inhibition of NOS-2 expression. Characteristics of this inhibition are: 1) local jejunal inflammation induced by T. spiralis systemically inhibits NOS-2 gene transcription, protein expression, and enzyme activity; 2) the inhibition blunts endotoxin-stimulated NOS-2 expression; 3) the inhibition does not extend to the expression of other isoforms of NOS, to paxillin, a housekeeper protein, or to cyclooxygenase-2, another protein induced by proinflammatory cytokines; 4) the inhibition is unlikely related to the formation of specific anti-parasite antibodies; and 5) the inhibition may involve substances other than stress-induced corticosteroids. Elucidation of such potent endogenous NOS-2 down-regulatory mechanisms could lead to the development of new strategies for the therapy of inflammatory conditions characterized by the overproduction of NO.
Mol Pharmacol 2001 Apr
PMID:Down-regulation of inducible nitric-oxide synthase (NOS-2) during parasite-induced gut inflammation: a path to identify a selective NOS-2 inhibitor. 1125 40

Hic-5 is a paxillin homologue that is localized to focal adhesion complexes. Hic-5 and paxillin share structural homology and interacting factors such as focal adhesion kinase (FAK), Pyk2/CAKbeta/RAFTK, and PTP-PEST. Here, we showed that Hic-5 inhibits integrin-mediated cell spreading on fibronectin in a competitive manner with paxillin in NIH 3T3 cells. The overexpression of Hic-5 sequestered FAK from paxillin, reduced tyrosine phosphorylation of paxillin and FAK, and prevented paxillin-Crk complex formation. In addition, Hic-5-mediated inhibition of spreading was not observed in mouse embryo fibroblasts (MEFs) derived from FAK(-/-) mice. The activity of c-Src following fibronectin stimulation was decreased by about 30% in Hic-5-expressing cells, and the effect of Hic-5 was restored by the overexpression of FAK and the constitutively active forms of Rho-family GTPases, Rac1 V12 and Cdc42 V12, but not RhoA V14. These observations suggested that Hic-5 inhibits cell spreading through competition with paxillin for FAK and subsequent prevention of downstream signal transduction. Moreover, expression of antisense Hic-5 increased spreading in primary MEFs. These results suggested that the counterbalance of paxillin and Hic-5 expression may be a novel mechanism regulating integrin-mediated signal transduction.
Mol Cell Biol 2001 Aug
PMID:Hic-5-reduced cell spreading on fibronectin: competitive effects between paxillin and Hic-5 through interaction with focal adhesion kinase. 1146 17

Hypertrophic terminally differentiated cardiac myocytes show increased sarcomeric organization and altered gene expression. Previously, we established a role for the nonreceptor tyrosine kinase Src in signaling cardiac myocyte hypertrophy. Here we report evidence that p130Cas (Cas) and focal adhesion kinase (FAK) regulate this process. In neonatal cardiac myocytes, tyrosine phosphorylation of Cas and FAK increased upon endothelin (ET) stimulation. FAK, Cas, and paxillin were localized in sarcomeric Z-lines, suggesting that the Z-line is an important signaling locus in these cells. Cas, alone or in cooperation with Src, modulated basal and ET-stimulated atrial natriuretic peptide (ANP) gene promoter activity, a marker of cardiac hypertrophy. Expression of the C-terminal focal adhesion-targeting domain of FAK interfered with localization of endogenous FAK to Z-lines. Expression of the Cas-binding proline-rich region 1 of FAK hindered association of Cas with FAK and impaired the structural stability of sarcomeres. Collectively, these results suggest that interaction of Cas with FAK, together with their localization to Z-lines, is critical to assembly of sarcomeric units in cardiac myocytes in culture. Moreover, expression of the focal adhesion-targeting and/or the Cas-binding proline-rich regions of FAK inhibited ANP promoter activity and suppressed ET-induced ANP and brain natriuretic peptide gene expression. In summary, assembly of signaling complexes that include the focal adhesion proteins Cas, FAK, and paxillin at Z-lines in the cardiac myocyte may regulate, either directly or indirectly, both cytoskeletal organization and gene expression associated with cardiac myocyte hypertrophy.
Mol Biol Cell 2001 Aug
PMID:Focal adhesion kinase and p130Cas mediate both sarcomeric organization and activation of genes associated with cardiac myocyte hypertrophy. 1151 17

Actin polymerization is accompanied by the formation of protein complexes that link extracellular signals to sites of actin assembly such as membrane ruffles and focal adhesions. One candidate recently implicated in these processes is the LIM domain protein zyxin, which can bind both Ena/vasodilator-stimulated phosphoprotein (VASP) proteins and the actin filament cross-linking protein alpha-actinin. To characterize the localization and dynamics of zyxin in detail, we generated both monoclonal antibodies and a green fluorescent protein (GFP)-fusion construct. The antibodies colocalized with ectopically expressed GFP-VASP at focal adhesions and along stress fibers, but failed to label lamellipodial and filopodial tips, which also recruit Ena/VASP proteins. Likewise, neither microinjected, fluorescently labeled zyxin antibodies nor ectopically expressed GFP-zyxin were recruited to these latter sites in live cells, whereas both probes incorporated into focal adhesions and stress fibers. Comparing the dynamics of zyxin with that of the focal adhesion protein vinculin revealed that both proteins incorporated simultaneously into newly formed adhesions. However, during spontaneous or induced focal adhesion disassembly, zyxin delocalization preceded that of either vinculin or paxillin. Together, these data identify zyxin as an early target for signals leading to adhesion disassembly, but exclude its role in recruiting Ena/VASP proteins to the tips of lamellipodia and filopodia.
Mol Biol Cell 2001 Oct
PMID:Zyxin is not colocalized with vasodilator-stimulated phosphoprotein (VASP) at lamellipodial tips and exhibits different dynamics to vinculin, paxillin, and VASP in focal adhesions. 1159 95

The integrin alpha9 subunit forms a single heterodimer, alpha9beta1. The alpha9 subunit is most closely related to the alpha4 subunit, and like alpha4 integrins, alpha9beta1 plays an important role in leukocyte migration. The alpha4 cytoplasmic domain preferentially enhances cell migration and inhibits cell spreading, effects that depend on interaction with the adaptor protein, paxillin. To determine whether the alpha9 cytoplasmic domain has similar effects, a series of chimeric and deleted alpha9 constructs were expressed in Chinese hamster ovary cells and tested for their effects on migration and spreading on an alpha9beta1-specific ligand. Like alpha4, the alpha9 cytoplasmic domain enhanced cell migration and inhibited cell spreading. Paxillin also specifically bound the alpha9 cytoplasmic domain and to a similar level as alpha4. In paxillin(-/-) cells, alpha9 failed to inhibit cell spreading as expected but surprisingly still enhanced cell migration. Further, mutations that abolished the alpha9-paxillin interaction prevented alpha9 from inhibiting cell spreading but had no effect on alpha9-dependent cell migration. These findings suggest that the mechanisms by which the cytoplasmic domains of integrin alpha subunits enhance migration and inhibit cell spreading are distinct and that the alpha9 and alpha4 cytoplasmic domains, despite sequence and functional similarities, enhance cell migration by different intracellular signaling pathways.
Mol Biol Cell 2001 Oct
PMID:The cytoplasmic domain of the integrin alpha9 subunit requires the adaptor protein paxillin to inhibit cell spreading but promotes cell migration in a paxillin-independent manner. 1159 4


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