EC:2.7.11.13 - FACTA Search

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

The ADAM (a disintegrin and metalloprotease) family consists of multidomain cell-surface proteins that have a major impact on cell behavior. These transmembrane-anchored proteins are synthesized as proforms that have (from the N terminus): a prodomain; a metalloprotease-, disintegrin-like-, cysteine-rich, epidermal growth factor-like, and transmembrane domain; and a cytoplasmic tail. The 90-kDa mature form of human ADAM12 is generated in the trans-Golgi through cleavage of the prodomain by a furin-peptidase and is stored intracellularly until translocation to the cell surface as a constitutively active protein. However, little is known about the regulation of ADAM12 cell-surface translocation. Here, we used human RD rhabdomyosarcoma cells, which express ADAM12 at the cell surface, in a temporal pattern. We report that protein kinase C (PKC) epsilon induces ADAM12 translocation to the cell surface and that catalytic activity of PKCepsilon is required for this translocation. The following results support this conclusion: 1) treatment of cells with 0.1 microM phorbol 12-myristate 13-acetate (PMA) enhanced ADAM12 cell-surface immunostaining, 2) ADAM12 and PKCepsilon could be co-immunoprecipitated from membrane-enriched fractions of PMA-treated cells, 3) RD cells transfected with EGFP-tagged, myristoylated PKCepsilon expressed more ADAM12 at the cell surface than did non-transfected cells, and 4) RD cells transfected with a kinase-inactive PKCepsilon mutant did not exhibit ADAM12 cell-surface translocation upon PMA treatment. Finally, we demonstrate that the C1 and C2 domains of PKCepsilon both contain a binding site for ADAM12. These studies show that PKCepsilon plays a critical role in the regulation of ADAM12 cell-surface expression.
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PMID:Regulation of ADAM12 cell-surface expression by protein kinase C epsilon. 1536 51

Betacellulin belongs to the family of epidermal growth factor-like growth factors that are expressed as transmembrane precursors and undergo proteolytic ectodomain shedding to release a soluble mature growth factor. In this study, we investigated the ectodomain shedding of the betacellulin precursor (pro-BTC) in conditionally immortalized wild-type (WT) and ADAM-deficient cell lines. Sequential ectodomain cleavage of the predominant cell-surface 40-kDa form of pro-BTC generated a major (26-28 kDa) and two minor (20 and 15 kDa) soluble forms and a cellular remnant lacking the ectodomain (12 kDa). Pro-BTC shedding was activated by calcium ionophore (A23187) and by the metalloprotease activator p-aminophenylmercuric acetate (APMA), but not by phorbol esters. Culturing cells in calcium-free medium or with the protein kinase Cdelta inhibitor rottlerin, but not with broad-based protein kinase C inhibitors, blocked A23187-activated pro-BTC shedding. These same treatments were without effect for constitutive and APMA-induced cleavage events. All pro-BTC shedding was blocked by treatment with a broad-spectrum metalloprotease inhibitor (GM6001). In addition, constitutive and activated pro-BTC shedding was differentially blocked by TIMP-1 or TIMP-3, but was insensitive to treatment with TIMP-2. Pro-BTC shedding was functional in cells from ADAM17- and ADAM9-deficient mice and in cells overexpressing WT or catalytically inactive ADAM17. In contrast, overexpression of WT ADAM10 enhanced constitutive and activated shedding of pro-BTC, whereas overexpression of catalytically inactive ADAM10 reduced shedding. These results demonstrate, for the first time, activated pro-BTC shedding in response to extracellular calcium influx and APMA and provide evidence that ADAM10 mediates constitutive and activated pro-BTC shedding.
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PMID:ADAM10 mediates ectodomain shedding of the betacellulin precursor activated by p-aminophenylmercuric acetate and extracellular calcium influx. 1550 48

Chimaerins are high affinity receptors for phorbol esters and diacylglycerol (DAG), unrelated to the protein kinase C isozymes. These receptors have deep implications in tumour biology since they regulate the activity of Rac1, a small GTP-binding protein of the Ras superfamily. It has been demonstrated that chimaerins have GTPase activating protein (GAP) activity, leading to the acceleration of GTP hydrolysis from Rac1 and therefore facilitating the transition to its inactive state. Rac regulates various cellular events, including gene transcription, cell cycle, adhesion and migration. It has also been described that Rac is implicated in the intracellular response to the binding of specific extracellular matrix proteins to integrin receptors. In this work, we analysed cell morphology, actin cytoskeleton reorganisation and metalloprotease (MMP) secretion in response to matrix proteins in mouse mammary carcinoma cells transfected with the beta2-chimaerin GAP domain. Overexpression of beta2-chimaerin induced important cytoskeletal rearrangements in response to matrix stimuli. Transfectant cells also showed activation of MMP-9 activity after stimulation with collagen IV and epidermal growth factor. The restitution of normal Rac levels by beta2-chimaerin activity induced an increase in the sensitivity of tumour cells to extracellular factors, suggesting a regression of the malignant phenotype.
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PMID:Role of beta2-chimaerin in the behaviour of murine mammary carcinoma cells in response to extracellular matrix components. 1558 33

The serotonin 5-hydroxytryptamine (5-HT4) receptor is of potential interest for the treatment of Alzheimer's disease because it increases memory and learning. In this study, we investigated the effect of zinc metalloprotease inhibitors on the amyloid precursor protein (APP) processing induced by the serotonin 5-HT4 receptor in vitro. We show that secretion of the non-amyloidogenic form of APP, sAPPalpha induced by the 5-HT4(e) receptor isoform was not due to a general boost of the constitutive secretory pathway but rather to its specific effect on alpha-secretase activity. Although the h5-HT4(e) receptor increased IP3 production, inhibition of PKC did not modify its effect on sAPPalpha secretion. In addition, we found that alpha secretase activity is regulated by the cAMP-regulated guanine nucleotide exchange factor, Epac and the small GTPase Rac.
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PMID:Regulation of the amyloid precursor protein ectodomain shedding by the 5-HT4 receptor and Epac. 1571 Apr 2

The amyloid precursor protein (APP) is proteolytically processed by beta- and gamma-secretases to release amyloid beta, the main component in senile plaques found in the brains of patients with Alzheimer disease. Alternatively, APP can be cleaved within the amyloid beta domain by alpha-secretase releasing the non-amyloidogenic product sAPP alpha, which has been shown to have neuroprotective properties. Several G protein-coupled receptors are known to activate alpha-secretase-dependent processing of APP; however, the role of G protein-coupled nucleotide receptors in APP processing has not been investigated. Here it is demonstrated that activation of the G protein-coupled P2Y2 receptor (P2Y2R) subtype expressed in human 1321N1 astrocytoma cells enhanced the release of sAPP alpha in a time- and dose-dependent manner. P2Y2 R-mediated sAPP alpha release was dependent on extracellular calcium but was not affected by 1,2-bis(2-aminophenoxy)ethane-N,N,N,-trimethylammonium salt, an intracellular calcium chelator, indicating that P2Y2R-stimulated intracellular calcium mobilization was not involved. Inhibition of protein kinase C (PKC) with GF109203 or by PKC down-regulation with phorbol ester pre-treatment had no effect on UTP-stimulated sAPP alpha release, indicating a PKC-independent mechanism. U0126, an inhibitor of the mitogen-activated protein kinase pathway, partially inhibited sAPPalpha release by UTP, whereas inhibitors of Src-dependent epidermal growth factor receptor transactivation by P2Y2Rs had no effect. The metalloprotease inhibitors phenanthroline and TAPI-2 and the furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethylketone also diminished UTP-induced sAPP alpha release. Furthermore, small interfering RNA silencing of an endogenous adamalysin, ADAM10 or ADAM17/TACE, partially suppressed P2Y2R-activated sAPP alpha release, whereas treatment of cells with both ADAM10 and ADAM17/TACE small interfering RNAs completely abolished UTP-activated sAPP alpha release. These results may contribute to an understanding of the non-amyloidogenic processing of APP.
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PMID:P2Y2 nucleotide receptors enhance alpha-secretase-dependent amyloid precursor protein processing. 1577 2

Regulated intramembrane proteolysis (RIP) represents an evolutionarily conserved process linking receptor function with transcriptional regulation. Best characterized by the Notch signaling pathway, RIP involves regulated ectodomain shedding followed by gamma-secretase-mediated release of the C-terminal, cytosolic domain. The C-terminus in turn translocates to the nucleus where it interacts with other proteins to regulate expression of specific genes. Recent studies in our laboratory have shown that megalin, a scavenger receptor in proximal tubule, is subjected to RIP in a manner very similar to that of Notch. We showed that megalin in subjected to protein kinase C-regulated, metalloprotease-mediated ectodomain shedding producing a membrane-associated C-terminal fragment (MCTF). The MCTF in turn forms the substrate for gamma-secretase. These data implicate megalin as a central element of a Notch-like signaling pathway linking protein reabsorption and gene regulation in proximal tubule. The likelihood that megalin processing plays an important role in the progression of proteinuric kidney disease is discussed.
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PMID:Regulated intramembrane proteolysis of megalin: linking urinary protein and gene regulation in proximal tubule? 1655 31

Soluble CD21 (sCD21), released from the plasma membrane by proteolytic cleavage (shedding) of its extracellular domain (ectodomain) blocks B cell/follicular dendritic cell interaction and activates monocytes. We show here that both serine- and metalloproteases are involved in CD21 shedding. Using the oxidant pervanadate to mimic B cell receptor activation and thiol antioxidants such as N-acetylcysteine (NAC) and glutathione (GSH) we show that CD21 shedding is a redox-regulated process inducible by oxidation presumably through activation of a tyrosine kinase-mediated signal pathway involving protein kinase C (PKC), and by reducing agents that either directly activate the metalloprotease and/or modify intramolecular disulfide bridges within CD21 and thereby facilitate access to the cleavage site. Lack of short consensus repeat 16 (SCR16) abolishes CD21 shedding, and opening of the disulfide bridge between cys-2 (Cys941) and cys-4 (Cys968) of SCR16 is a prerequisite for CD21 shedding. Replacing these cysteines with selenocysteines (thereby changing the redox potential from -180 to -381 mV) results in a loss of inducible CD21 shedding, and removing this bridge by exchanging these cysteines with methionines increases CD21 shedding.
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PMID:Redox regulation of CD21 shedding involves signaling via PKC and indicates the formation of a juxtamembrane stalk. 1680 74

The amyloid precursor protein (APP) is cleaved enzymatically by nonamyloidogenic and amyloidogenic pathways. alpha-Secretase (alpha-secretase), cleaves APP within the beta-amyloid (Abeta) sequence, resulting in the release of a secreted fragment of APP (alphaAPPs) and precluding Abeta generation. In this study, we investigated the effects of an acetylcholinesterase inhibitor, huperzine A (Hup A), on APP processing and Abeta generation in human embryonic kidney 293 cells transfected with human APP bearing the Swedish mutation (HEK293 APPsw). Hup A dose dependently (0-10 microM) increased alphaAPPs release and membrane-coupled APP CTF-C83, suggesting increased APP metabolism toward the nonamyloidogenic alpha-secretase pathway. The metalloprotease inhibitor TAPI-2 inhibited the Hup A-induced increase in alphaAPPs release, further suggesting a modulatory effect of Hup A on alpha-secretase activity. The synthesis of full-length APP and cell viability were unchanged after Hup A incubation, whereas the level of Abeta(Total) was significantly decreased, suggesting an inhibitory effect of Hup A on Abeta production. Hup A-induced alphaAPPs release was significantly reduced by the protein kinase C (PKC) inhibitors GF109203X and Calphostin C. These data, together with the finding that the PKCalpha level was enhanced prior to the increase of alphaAPPs secretion, indicate that PKC may be involved in Hup A-induced alphaAPPs secretion by HEK293 APPsw cells. Our data suggest alternative pharmacological mechanisms of Hup A relevant to the treatment of Alzheimer's disease.
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PMID:Effects of huperzine A on amyloid precursor protein processing and beta-amyloid generation in human embryonic kidney 293 APP Swedish mutant cells. 1686 48

Alpha-secretase (alpha-secretase), cleaves the amyloid precursor protein (APP) within the amyloid-beta (Abeta) sequence, resulting in the release of a secreted fragment of APP (alphaAPPs) and precluding Abeta generation. We investigated the effects of the acetylcholinesterase inhibitor, huperzine A (Hup A), on APP processing and Abeta generation in human neuroblastoma SK-N-SH cells overexpressing wild-type human APP695. Hup A dose-dependently (0-10 microM) increased alphaAPPs release. Therefore, we evaluated two alpha-secretase candidates, a disintegrin and metalloprotease (ADAM) 10 and ADAM17 in Hup A-induced non-amyloidogenic APP metabolism. Hup A enhanced the level of ADAM10, and the inhibitor of tumor necrosis factor-alpha converting enzyme (TACE)/ADAM17 inhibited the Hup A-induced rise in alphaAPPs levels, further suggesting Hup A directed APP metabolism toward the non-amyloidogenic alpha-secretase pathway. Hup A had no effect on Abeta generation in this cell line. The steady-state levels of full-length APP and cell viability were unaffected by Hup A. Alpha-APPs release induced by Hup A treatment was significantly reduced by muscarinic acetylcholine receptor antagonists (particularly by an M1 antagonist), protein kinase C (PKC) inhibitors, GF109203X and calphostin C, and the mitogen-activated kinase kinase (MEK) inhibitors, U0126 and PD98059. Furthermore, Hup A markedly increased the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase, which was blocked by treatment with U0126 and PD98059. In addition, Hup A inhibited acetylcholinesterase activity by 20% in neuroblastoma cells. Our results indicate that the activation of muscarinic acetylcholine receptors, PKC and MAP kinase may be involved in Hup A-induced alphaAPPs secretion in neuroblastoma cells and suggest multiple pharmacological mechanisms of Hup A regarding the treatment of Alzheimer's disease (AD).
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PMID:Huperzine A regulates amyloid precursor protein processing via protein kinase C and mitogen-activated protein kinase pathways in neuroblastoma SK-N-SH cells over-expressing wild type human amyloid precursor protein 695. 1794 34

Alzheimer's disease (AD) is the most prevalent form of dementia, and its effective disease modifying therapies are desperately needed. Promotion of non-amyloidogenic alpha-secretase cleavage of amyloid precursor protein (APP) to release soluble sAPPalpha, based on the most widely accepted "amyloid model" as a plausible mechanism for AD treatment, is the focus of this review. Modulation of alpha-secretase or "a disintegrin and metalloprotease (ADAM)"s activity via protein kinase C (PKC), calcium ion (Ca(2+)), tyrosine kinase (TK), MAP kinase (MAPK), and hormonal signaling, which regulate catabolic processing of APP, are discussed. The inhibition of amyloidogenic processing of APP by the beta- and gamma-secretase has been considered till now a promising strategy to treat AD. But beta- and gamma-secretase inhibitors, along with the available therapeutic tools for AD, have side effects. These challenges can be circumvented to certain extent; but activation of sAPPalpha release appears to be a potential alternative strategy to reduce cerebral amyloidosis. Drug screens have been performed to identify therapeutics for AD, but an effective screening strategy to isolate activators of alpha-secretase has been rarely reported. Novel reporter-based screens targeted toward APP mRNA 5' untranslated region (UTR), followed by counter-screens to detect alpha-secretase stimulators, could be important in detecting compounds to promote sAPPalpha release and reduce amyloid beta (Abeta) buildup. The primary inflammatory cytokine interleukin-1, which stimulates APP 5'UTR-directed translation of cell-associated APP, enhances processing to sAPPalpha in astrocytes and co-activates ADAM-10/ADAM-17 through MAPK signaling; thus illustrating a novel pathway that could serve as therapeutic model for AD.
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PMID:Role of the APP non-amyloidogenic signaling pathway and targeting alpha-secretase as an alternative drug target for treatment of Alzheimer's disease. 1804 31

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