Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.13 (protein kinase C)
 49,245 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Addition of 1-oleoyl-lysophosphatidic acid (LPA) induces tyrosine phosphorylation of multiple substrates in Swiss 3T3 cells including bands of M(r) 110,000-130,000 and M(r) 70,000-80,000. An increase in tyrosine phosphorylation of the M(r) 110,000-130,000 cluster of bands was detected as soon as 30 s after LPA stimulation reaching a maximum within 1 min. LPA stimulated tyrosine phosphorylation of all bands in a concentration-dependent fashion; a half-maximal effect occurred at 30 nM. Immunoprecipitation of lysates of LPA-treated cells with monoclonal antibodies that specifically recognize focal adhesion kinase (p125FAK), paxillin, and p130 revealed that these proteins are prominent substrates for LPA-stimulated tyrosine phosphorylation. Down-regulation of protein kinase C (PKC) by prolonged pretreatment with phorbol 12,13-dibutyrate, selective inhibition of PKC by GF109203X, or depletion of the intracellular Ca2+ pool by thapsigargin had no effect on LPA-stimulated tyrosine phosphorylation. Thus, protein tyrosine phosphorylation by LPA is largely independent of either the PKC or Ca2+ pathways. In contrast, pretreatment of the cells with cytochalasin D, which selectively disrupts the network of the actin filaments, completely inhibited LPA-induced tyrosine phosphorylation. Furthermore, tyrosine phosphorylation of p125FAK induced by LPA was completely prevented when cells were stimulated in the presence of platelet-derived growth factor at a concentration (30 ng/ml) that causes disruption of actin stress fibers. This suggests that the integrity of the actin cytoskeleton is essential for LPA-induced tyrosine phosphorylation and reveals a novel cross-talk between LPA and platelet-derived growth factor on p125FAK tyrosine phosphorylation.
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PMID:Lysophosphatidic acid stimulates tyrosine phosphorylation of focal adhesion kinase, paxillin, and p130. Signaling pathways and cross-talk with platelet-derived growth factor. 751 Jul 8

These findings have important implications for signal transduction and cell regulation. Most obviously, they suggest that tyrosine phosphorylation of a novel type of tyrosine kinase p125FAK is a point of convergence in the action of integrins, oncogenic forms of pp60src, mitogenic neuropeptides and growth factors (Fig. 3). One inference is that the signal transduction pathways initiated by these diverse groups of molecules have, at least in part, similar consequences for cellular function. The notion of convergence is reinforced by the striking similarity in the overall pattern of tyrosine phosphorylation produced through these different pathways. It is tempting to speculate that p125FAK, paxillin and p130 are components in a common programme of phosphorylation events stimulated by integrins, mitogenic neuropeptides and growth factors. The localization of p125FAK to focal adhesions is clearly consistent with a role for this protein as a junction point in the transduction of signals that regulate cell substrate adhesion and ultimately cell motility and cell shape, as suggested in Fig. 3. The existence of distinct pathways leading to p125FAK phosphorylation raises the possibility of synergistic interactions between integrins and G protein coupled receptors. In fact, integrin mediated p125FAK tyrosine phosphorylation appears to be mediated by a PKC dependent pathway (Vuori and Ruoslathi, 1993). By contrast, bombesin and LPA induce tyrosine phosphorylation of p125FAK and paxillin through a PKC independent pathway (Sinnett-Smith et al, 1993; Zachary et al, 1993; Seufferlein and Rozengurt, 1994). It is possible that tyrosine phosphorylation of p125FAK by bombesin, LPA and pp60v-src bypasses and perhaps mimics the phosphorylation caused by integrin activation. Further experimental work will be required to elucidate whether integrins and neuropeptides increase the autophosphorylation of Tyr-397 in p125FAK, as has been recently demonstrated in src-transformed cells (Schaller et al, 1994). Thus, molecular and cellular aspects of the role of p125FAK in signal transduction remain unclear. Specifically, the molecular steps by which different receptors (integrins, seven transmembrane domain receptors and tyrosine kinase receptors) can transduce signals leading to p125FAK tyrosine phosphorylation and the precise role of p125FAK in cell regulation are important areas for further research. Identification of the substrates of p125FAK, which given its localization are likely to reside in or be associated with focal adhesion, will be crucial for elucidating its role in cell regulation.
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PMID:Convergent signalling in the action of integrins, neuropeptides, growth factors and oncogenes. 755 64

We have previously shown that protein phosphorylation plays an important role in the sorting and assembly of tight junctions. We have now examined in detail the role of protein kinases in intercellular junction biogenesis by using a combination of highly specific and broad-spectrum inhibitors that act by independent mechanisms. Our data indicate that protein kinase C (PKC) is required for the proper assembly of tight junctions. Low concentrations of the specific inhibitor of PKC, calphostin C, markedly inhibited development of transepithelial electrical resistance, a functional measure of tight-junction biogenesis. The effect of PKC inhibitors on the development of tight junctions, as measured by resistance, was paralleled by a delay in the sorting of the tight-junction protein, zona occludens 1 (ZO-1), to the tight junction. The assembly of desmosomes and the adherens junction were not detectably affected, as determined by immunocytochemical analysis. In addition, ZO-1 was phosphorylated subsequent to the initiation of cell-cell contact, and treatment with calphostin C prevented approximately 85% of the phosphorylation increase. Furthermore, in vitro measurements indicate that ZO-1 may be a direct target of PKC. Moreover, membrane-associated PKC activity more than doubled during junction assembly, and immunocytochemical analysis revealed a pool of PKC zeta that appeared to colocalize with ZO-1 at the tight junction. A preformed complex containing ZO-1, ZO-2, p130, as well as 330- and 65-kDa phosphoproteins was detected by coimmunoprecipitation in both the presence and absence of cell-cell contact. Identity of the 330- and 65-kDa phosphoproteins remains to be determined, but the 65-kDa protein may be occludin. The mass of this complex and the incorporation of ZO-1 into the Triton X-100-insoluble cytoskeleton were not PKC dependent.
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PMID:Regulated assembly of tight junctions by protein kinase C. 759 83

In this study we examined the involvement of the focal adhesion-associated proteins p125FAK and paxillin as substrates for bradykinin (BK)-stimulated tyrosine phosphorylation in Swiss 3T3 cells and the potential role of protein kinase C and Ca2+ in these events. BK (1 microM) stimulated tyrosine phosphorylation of p125FAK and paxillin. In addition, BK also increased the phosphotyrosine content of the src transformation-associated protein p130. The responses were rapid and transient and peaked at approximately 1 min after BK addition. Furthermore, the responses were dose-dependent with half-maximal effects occurring at 1-10 nM BK. The phosphotyrosine content of p125FAK, paxillin, and p130 was also increased following stimulation with phorbol 12-myristate 13-acetate (PMA) (0.1 microM). In contrast, PMA had no effect on the phosphotyrosine content of p125, a Ras-GAP-associated tyrosine phosphoprotein that we recently identified. Long term pretreatment (18 h) of cells with 0.3 microM PMA partially attenuated BK-stimulated phosphorylation of p125FAK but was without effect on phosphorylation of paxillin and Ras-GAP-associated p125. Furthermore, only a small inhibition of BK- and PMA-stimulated phosphorylation of p125FAK was observed following pretreatment with 25 microM BAPTA/AM. In all, these results show that multiple mechanisms are involved in BK-stimulated tyrosine phosphorylation of p125FAK, paxillin, Ras-GAP-associated p125, and src transformation-associated p130.
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PMID:Focal adhesion-associated proteins p125FAK and paxillin are substrates for bradykinin-stimulated tyrosine phosphorylation in Swiss 3T3 cells. 792 90

Endothelin-1 (ET-1) binding to ETB receptors increases the activity of the apical membrane Na+/H+ antiporter (NHE3) of renal proximal tubule and cultured OKP cells. In OKPETB6 cells, a clonal cell line of OKP cells that overexpresses ETB receptors, ET-1-induced increases in Na+/H+ antiporter activity are mediated 50% by Ca2(+)-dependent pathways and 50% by tyrosine kinase pathways. ET-1 induces tyrosine phosphorylation of proteins of 68, 110, 125, 130, and 210 kDa. ET-1-induced tyrosine phosphorylation is mediated by the ETB receptor and is not dependent on increases in cell Ca2+ or protein kinase C. The 68-, 110-, 125-, and 130-kDa phosphoproteins are cytosolic, whereas the 210-kDa phosphoprotein is an integral membrane protein. Immunoprecipitation studies showed that the 68-kDa protein is paxillin and the 125-kDa protein is p125FAK (focal adhesion kinase). Cytochalasin D, which disrupts focal adhesions, prevented ET-1-induced tyrosine phosphorylation of paxillin, p110, p125FAK, and p130 but did not prevent tyrosine phosphorylation of p210 and did not prevent ET-1-induced increases in Na+/H+ antiporter activity. Thus 50% of ETB receptor-induced Na+/H+ antiporter activation is mediated by tyrosine kinase pathways, possibly involving p210. ETB receptor activation also induces tyrosine phosphorylation of focal adhesion proteins, but this is not required for antiporter activation.
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PMID:Role of tyrosine kinase pathways in ETB receptor activation of NHE3. 884 5

Treatment of Swiss 3T3 cells with bombesin rapidly induced tyrosine phosphorylation of the p130 Crk-associated substrate (p130(cas)). Vasopressin, endothelin, bradykinin, lysophosphatidic acid, sphingosylphosphorylcholine, and phorbol 12,13-dibutyrate also stimulated p130(cas) tyrosine phosphorylation. Bombesin-induced p130(cas) tyrosine phosphorylation could be dissociated from both protein kinase C activation and Ca2+ mobilization from intracellular stores. In contrast, cytochalasin D, which disrupts the network of actin microfilaments, completely prevented tyrosine phosphorylation of p130(cas) by bombesin. Platelet-derived growth factor, at low concentrations (1-5 ng/ml), also induced tyrosine phosphorylation of p130(cas) via a pathway that depended on the integrity of the actin cytoskeleton. The phosphatidylinositol 3'-kinase inhibitors wortmannin and LY294002 prevented tyrosine phosphorylation of p130(cas) in response to platelet-derived growth factor but not in response to neuropeptides, lysophosphatidic acid, sphingosylphosphorylcholine, or phorbol 12,13-dibutyrate. All agonists that induced p130(cas) tyrosine phosphorylation also promoted the formation of a p130(cas).Crk complex in intact Swiss 3T3 cells. Thus, our results identified distinct signal transduction pathways that lead to tyrosine phosphorylation of p130(cas) in the same cells and suggest that p130(cas) could play a role in mitogen-mediated signal transduction.
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PMID:Tyrosine phosphorylation of p130(cas) by bombesin, lysophosphatidic acid, phorbol esters, and platelet-derived growth factor. Signaling pathways and formation of a p130(cas)-Crk complex. 908 73

Lysophosphatidylcholine (lyso-PC), a biologically active phospholipid, appears to modulate various endothelial cell functions through tyrosine kinase-dependent signaling pathways. In cultured bovine aortic endothelial cells (BAEC), we have found that a 130 kDa protein (p130) was rapidly tyrosine phosphorylated within 2 min and sustained for, at least, 1 hr in response to 10 mumol/L of lyso-PC but not to phorbol myristate acetate (PMA). Prolonged preexposure to PMA did not affect lyso-PC-induced p130 tyrosine phosphorylation, suggesting that mechanisms independent of protein kinase C may be involved. Fractionation of the cell lysates revealed that p130 was detectable in the membrane fraction but not in the cytosolic fraction. Immunoprecipitation followed by immunoblotting of lyso-PC-treated BAEC identified p130 as bovine PECAM-1. Tyrosine phosphorylation of PECAM-1 appears to be one of the earliest events elicited by lyso-PC, and may play a role in lyso-PC-induced modulation of endothelial functions.
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PMID:Tyrosine phosphorylation of platelet endothelial cell adhesion molecule-1 induced by lysophosphatidylcholine in cultured endothelial cells. 950 Oct 20

The tight junction creates a regulated barrier in the paracellular pathway and, together with the actin-rich adherens junction, forms a functional unit called the apical junction complex. A growing number of tight junction-associated proteins have been identified, but functions are defined for only a few. The intercellular barrier is formed by rows of the transmembrane protein occludin, which is bound on the cytoplasmic surface to ZO-1 and ZO-2. These proteins are members of the membrane-associated guanylate kinase (MAGUK) protein family and are likely to have both structural and signaling roles. Junctional plaque proteins without known functions include cingulin, p130, and 7H6; single reports describe ZA-1TJ and symplekin. Many cellular signaling pathways affect assembly and sealing of junctions. Transducing proteins, which localize within the junction, include both heterotrimeric and rho-related GTP-binding proteins, PKC-zeta and nonreceptor tyrosine kinases. Control of perijunctional actin may be the unifying mechanism for regulating paracellular permeability.
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PMID:Molecular architecture of tight junctions. 955 57

Addition of insulin growth factor-I (IGF-I) to quiescent Swiss 3T3 cells rapidly induced tyrosine phosphorylation of the p130Crk-associated substrate (p130(Cas)), a novel adaptor protein localized at focal adhesions. Half-maximal effect was obtained at 0. 6 nM. IGF-I also promoted the formation of a complex between p130(Cas) and c-Crk and elicited a parallel increase in the tyrosine phosphorylation of p125(Fak) and paxillin. IGF-I-induced p130(Cas), p125(Fak), and paxillin tyrosine phosphorylation could be dissociated from mitogen-activated protein kinase kinase, p70(S6K), and protein kinase C activation. In contrast, the structurally unrelated phosphatidylinositol 3-kinase inhibitors wortmannin and LY294002 markedly attenuated the increase in tyrosine phosphorylation of p130(Cas), p125(Fak), and paxillin induced by IGF-I. Cytochalasin D, which disrupts the network of actin microfilaments, completely prevented tyrosine phosphorylation of p130(Cas), p125(Fak), and paxillin and the formation of a p130(Cas). Crk complex in response to IGF-I. Thus, our results identified a phosphatidylinositol 3-kinase-dependent pathway that requires the integrity of the actin cytoskeleton to induce tyrosine phosphorylation of p130(Cas), p125(Fak), and paxillin in response to IGF-I and suggest that tyrosine phosphorylation of these focal adhesion proteins, together with the recruitment of c-Crk into a complex with p130(Cas), may play a novel role in IGF-I signal transduction.
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PMID:Insulin-like growth factor I stimulates tyrosine phosphorylation of p130(Cas), focal adhesion kinase, and paxillin. Role of phosphatidylinositol 3'-kinase and formation of a p130(Cas).Crk complex. 974 96

p130(Cas) (Crk-associated substrate), because of its structure as an adapter protein, can interact when tyrosine-phosphorylated with a large number of cellular proteins and therefore be an important modulator of downstream signals. A number of growth factors, lipids, and a few G protein-coupled receptors can stimulate p130(Cas) tyrosine phosphorylation. Recent studies show that tyrosine phosohorylation of intracellular proteins by the hormone/neurotransmitter cholecystokinin (CCK) in rat pancreatic acinar cells may be an important signaling cascade. In this study, we show in rat dispersed pancreatic acini CCK-8 rapidly stimulates tyrosine phosphorylation of p130(Cas), reaching a maximum (6.6 +/- 1. 4)-fold increase with a half-maximal effect at 0.3 nM. Activation of protein kinase C by TPA or increases in [Ca2+]i by the calcium ionophore A23187 stimulated p130(Cas) phosphorylation. Blockade of CCK increases in [Ca2+]i or PKC activity did not alter CCK-8-stimulated p130(Cas) phosphorylation; however, simultaneous blockage of both cascades caused a 50% inhibition. Partial inactivation by C. botulinum toxin of the small GTP-binding protein Rho caused a 41 +/- 12% decrease in the CCK-stimulated p130(Cas) phosphorylation. Disruption of the actin cytoskeleton with cytochalasin D, but not the microtubule network with colchicine, completely inhibited CCK-8-stimulated p130(Cas) phosphorylation. Total p130(Cas) under basal conditions was largely localized (70 +/- 2%) in the membrane fraction, and stimulation with CCK-8 induced total p130(Cas) translocation from the cytosolic fraction. CCK stimulation also caused a (5 +/- 1)-fold increase in p130(Cas) tyrosine phosphorylated in the plasma membrane. Treatment with tyrphostin B44 inhibited CCK-8-stimulated p130(Cas) phosphorylation, but it had no effect on p130(Cas) translocation. CCK-8 caused rapid formation of a p130(Cas)-Crk complex. In conclusion, our results demonstrate CCKA receptor activation causes rapid tyrosine phosphorylation of p130(Cas) through PLC-dependent and -independent mechanisms that require the participation of the small GTP-binding protein Rho and the integrity of the actin cytoskeleton, but not the microtubule network. Moreover, CCKA receptor activation causes translocation of p130(Cas) to the membrane and an increase in membrane tyrosine-phosphorylated p130(Cas). The translocation to the membrane does not require antecedent tyrosine phosphorylation. CCKA activation promotes the rapid formation of a p130(Cas)-Crk complex. These results suggest that p130(Cas) is likely an important modulator of downstream signals activated by CCK-8, possibly involved in regulating numerous cellular effects, such as effects on cell growth or cell shape.
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PMID:CCKA receptor activation stimulates p130(Cas) tyrosine phosphorylation, translocation, and association with Crk in rat pancreatic acinar cells. 993 Oct 15


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