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)

Angiotensin-converting enzyme (ACE), a type I integral membrane protein that plays a major role in vasoactive peptide metabolism, is shed from the plasma membrane by proteolytic cleavage within the juxtamembrane stalk. To investigate whether this shedding is regulated by lateral segregation in cholesterol-rich lipid rafts, Chinese hamster ovary cells and human neuroblastoma SH-SY5Y cells were transfected with either wild-type ACE (WT-ACE) or a construct with a glycosylphosphatidylinositol (GPI) anchor attachment signal replacing the transmembrane and cytosolic domains (GPI-ACE). In both cell types, GPI-ACE, but not WT-ACE, was sequestered in caveolin or flotillin-enriched lipid rafts and was released from the cell surface by treatment with phosphatidylinositol-specific phospholipase C. When cells were treated with activators of the protein kinase C signalling cascade (phorbol myristate acetate or carbachol) the shedding of GPI-ACE was stimulated to a similar extent to that of WT-ACE. The release of WT-ACE and GPI-ACE from the cells was inhibited in an identical manner by a range of hydroxamate-based zinc metalloprotease inhibitors. Disruption of lipid rafts by filipin treatment did not alter the shedding of GPI-ACE, and phorbol ester treatment did not alter the distribution of WT-ACE or GPI-ACE between raft and non-raft membrane compartments. These data clearly show that the protein kinase C-stimulated shedding of ACE does not require the transmembrane or cytosolic regions of the protein, and that sequestration in lipid rafts does not regulate the shedding of the protein.
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PMID:The ectodomain shedding of angiotensin-converting enzyme is independent of its localisation in lipid rafts. 1279 21

Two novel neuroprotective cholinesterase (ChE) inhibitors, TV3326 and TV3279 [(N-propargyl-(3R) and (3S) aminoindan-5-yl)-ethyl methyl carbamate], respectively were derived from rasagiline, for the treatment of Alzheimer's disease (AD). TV3326 also inhibits monoamine oxidase (MAO)-A and B, while its S-isomer, TV3279, lacks MAO-inhibitory activity. The actions of these drugs in the regulation of the amyloid precursor protein (APP) processing using rat PC12 and human SH-SY5Y neuroblastoma cells were examined. Both isomers stimulated the release of the non-amyloidogenic alpha-secretase form of soluble APP (sAPPalpha) from these cell lines. The increases in sAPPalpha, induced by TV3326 and TV3279, were dose-dependent (0.1-100 micro M) and blocked by the hydroxamic acid-based metalloprotease inhibitor, Ro31-9790, suggesting mediation via alpha-secretase activity. Using several signal transduction inhibitors, the involvement of protein kinase C (PKC), mitogen-activated protein (MAP) kinase, and tyrosine kinase-dependent pathways in the enhancement of sAPPalpha release by TV3326 and TV3279 was identified. In addition, both drugs directly induced the phosphorylation of p44 and p42 MAP kinase, which was abolished by the specific inhibitors of MAP kinase activation, PD98059 and U0126. These data suggest a novel pharmacological mechanism, whereby these ChE inhibitors regulate the secretary processes of APP via activation of the MAP kinase pathway.
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PMID:Amyloid processing and signal transduction properties of antiparkinson-antialzheimer neuroprotective drugs rasagiline and TV3326. 1285 32

Shedding of proteins localized at the cell surface is an important regulatory step in the function of many of these proteins. Human meprin (N-benzoyl-l-tyrosyl-p-aminobenzoic acid hydrolase, PPH, EC 3.4.24.18) a zinc-metalloendopeptidase of the astacin family is an oligomeric protein complex of alpha- and beta-subunits and is expressed abundantly in the intestine and kidney as well as in leukocytes of the lamina propria and in cancer cells. In transfected cells intracellular proteolytic removal of the membrane anchor results in the secretion of the meprin alpha-subunit. In rats and mice, the beta-subunit exists in a membrane-anchored form. In contrast, human meprinbeta is constitutively converted into a secretable form. We now show that phorbol 12-myristate 13-acetate (PMA) stimulates an increased release of hmeprinbeta from transfected COS-1 cells, whereas hmeprinalpha secretion is not influenced. This stimulatory effect is inhibited by the protein kinase C (PKC) inhibitor staurosporine, suggesting that activation of PKC mediates PMA-induced hmeprinbeta shedding. The use of different protease inhibitors shows that two different metalloprotease activities are responsible for the constitutive and the PMA-stimulated hmeprinbeta shedding. We identified tumor necrosis factor alpha-converting enzyme (TACE or ADAM17) as the protease that mediates the PMA-induced release. We also demonstrate that hmeprinbeta is phosphorylated by PMA treatment on Ser687 within a PKC consensus sequence in the cytosolic domain of the protein. This phosphorylation of hmeprinbeta is not, however, implicated in the enhanced secretion by PMA treatment.
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PMID:Phorbol 12-myristate 13-acetate-induced ectodomain shedding and phosphorylation of the human meprinbeta metalloprotease. 1294 54

Epidermal growth factor receptor (EGFR) ligands are synthesized as type I membrane protein precursors exposed at the cell surface. Shedding of the ectodomain of these proteins is the way cells regulate the equilibrium between cell-associated and diffusible forms of these growth factors. Whereas the regulated shedding of transforming growth factor-alpha, HB-EGF, and amphiregulin precursors have been clearly established, regulation of full-length pro-EGF shedding has not been clearly demonstrated. Here, using both wild-type and M2 mutant CHO-K1 as well as HeLa cell lines transiently transfected with epitope-tagged rat pro-EGF expression plasmid, we demonstrate that these cells synthesize EGF as a high molecular weight membrane-associated precursor glycoprotein expressed at the cell surface. All cell lines are able to release the entire ectodomain of pro-EGF in the extracellular medium following juxtamembrane cleavage of the precursor once it is present at the cell surface. More significantly we clearly established that CHO-M2 and HeLa cells only constitutively release low levels of pro-EGF. This shedding is a regulated phenomenon in wild-type CHO cells where it can be induced by different agents such as phorbol 12-myristate 13-acetate (PMA), pervanadate, and serum but not by calcium ionophores. Using specific inhibitors as well as protein kinase C (PKC) depletion, PMA stimulation was shown to be completely dependent on PKC activation whereas pervanadate and serum stimulation were not. Regulated ectodomain shedding involves the activity of a zinc metalloprotease as determined by inhibition with phenantrolin and TAPI-2 and by the results obtained with the CHO-M2 shedding defective mutant cell line. Comparison of the ability of CHO and HeLa cell lines to shed pro-EGF and pro-TNF-alpha upon stimulation greatly suggests that TACE (ADAM 17) may not be the ectoprotease involved in the secretion of pro-EGF ectodomain and that this protease, which remains to be identified, shows a restricted cellular expression pattern.
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PMID:Regulated cell surface pro-EGF ectodomain shedding is a zinc metalloprotease-dependent process. 1294 92

Rasagiline [N-propargyl-(1R)-aminoindan] a highly potent selective irreversible monoamine oxidase (MAO)-B inhibitor exerts neuroprotective and antiapoptotic effects against a variety of insults in cell cultures and in vivo and has finished its phase III clinical trials for Parkinson's disease. In the present study, we show that rasagiline (1 and 10 microM) significantly protected rat PC12 cells against beta-amyloid (Abeta1-42) toxicity. In addition, rasagiline significantly increased (approximately threefold) the secretion of the nonamyloidogenic soluble form of the amyloid precursor protein (sAPPalpha) from SH-SY5Y neuroblastoma and PC12 cells. The increase of sAPPalpha was dose-dependent and was blocked by the hydroxamic acid-based metalloprotease inhibitor Ro31-9790 (100 microM), suggesting that the effect is mediated via alpha-secretase activity. Rasagiline-induced sAPPalpha release was significantly reduced by the inhibitors of protein kinase C (PKC), GF109203X, and ERK mitogen-activated protein kinase (MAPK) PD98059. Moreover, rasagiline dose dependently (0.1-10 microM) increased the phosphorylation of p44 and p42 MAPK, which was abolished by PD98059 (30 microM) and GF109203X (2.5 microM). By comparing the actions of rasagiline with those of its S-isomer TVP1022, which is not an MAO inhibitor, we have been able to demonstrate that MAO-B inhibition is not a prerequisite for either sAPPalpha-induced release or ERK phosphorylation. In addition, structure-activity relationship among rasagiline-related compounds suggests the crucial role of the propargyl moiety in these molecules, because propargylamine itself significantly induced the secretion of sAPPalpha and increased MAPK phosphorylation with similar potency to that of rasagiline and its derivatives.
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PMID:The importance of propargylamine moiety in the anti-Parkinson drug rasagiline and its derivatives in MAPK-dependent amyloid precursor protein processing. 1452 44

Protein kinase Cepsilon (PKCepsilon), a Ca(2+)-independent, phospholipid-dependent serine/threonine kinase, is among the PKC isoforms expressed in mouse epidermis. We reported that FVB/N transgenic mice that overexpress ( approximately 18-fold) PKCepsilon protein in basal epidermal cells and cells of the hair follicle develop papilloma-independent metastatic squamous cell carcinoma (mSCC) elicited by 7,12-dimethylbenz(a)anthracene-initiation and 12-O-tetradecanoylphorbol-13-acetate (TPA)-promotion protocol. We now present that PKCepsilon transgenic mice elicit elevated serum tumor necrosis factor (TNF)alpha levels during skin tumor promotion by TPA, and this increase may be linked to the development of mSCC. A single topical application of TPA (5 nmol) to the skin, as early as 2.5 h after treatment, resulted in a significant (P < 0.01) increase (2-fold) in epidermal TNFalpha and more than a 6-fold increase in ectodomain shedding of TNFalpha into the serum of PKCepsilon transgenic mice relative to their wild-type littermates. Furthermore, this TPA-stimulated TNFalpha shedding was proportional to the level of expression of PKCepsilon in the epidermis. Using the TNF-alpha converting enzyme (TACE) inhibitor, TAPI-1, TPA-stimulated TNFalpha shedding could be completely prevented in PKCepsilon transgenic mice and isolated keratinocytes. These results indicate that PKCepsilon signal transduction pathways to TPA-stimulated TNFalpha ectodomain shedding are mediated by TACE, a transmembrane metalloprotease. Using the superoxide dismutase mimetic CuDIPs and the glutathione reductase mimetic ebselen, TPA-stimulated TNFalpha shedding from PKCepsilon transgenic mice could be completely attenuated, implying the role of reactive oxygen species. Finally, i.p. injection of a TNFalpha synthesis inhibitor, pentoxifylline, during skin tumor promotion completely prevented the development of mSCC in PKCepsilon transgenic mice. Taken together, these results indicate that: (a) PKCepsilon activation is an initial signal in TPA-induced shedding of TNFalpha from epidermal keratinocytes; (b) PKCepsilon-mediated signals to TACE are possibly mediated through reactive oxygen species; and (c) TPA-induced TNFalpha shedding may play a role in the development of mSCC in PKCepsilon transgenic mice.
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PMID:Protein kinase Cepsilon is linked to 12-O-tetradecanoylphorbol-13-acetate-induced tumor necrosis factor-alpha ectodomain shedding and the development of metastatic squamous cell carcinoma in protein kinase Cepsilon transgenic mice. 1455 50

Numerous external stimuli, including G protein-coupled receptor agonists, cytokines, growth factors, and steroids activate mitogen-activated protein kinases (MAPKs) through phosphorylation of the epidermal growth factor receptor (EGF-R). In immortalized hypothalamic neurons (GT1-7 cells), agonist binding to the gonadotropin-releasing hormone receptor (GnRH-R) causes phosphorylation of MAPKs that is mediated by protein kinase C (PKC)-dependent transactivation of the EGF-R. An analysis of the mechanisms involved in this process showed that GnRH stimulation of GT1-7 cells causes release/shedding of the soluble ligand, heparin binding epidermal growth factor (HB-EGF), as a consequence of metalloprotease activation. GnRH-induced phosphorylation of the EGF-R and, subsequently, of Shc, ERK1/2, and its dependent protein, p90RSK-1 (p90 ribosomal S6 kinase 1 or RSK-1), was abolished by metalloprotease inhibition. Similarly, blockade of the effect of HB-EGF with the selective inhibitor CRM197 or a neutralizing antibody attenuated signals generated by GnRH and phorbol 12-myristate 13-acetate, but not those stimulated by EGF. In contrast, phosphorylation of the EGF-R, Shc, and ERK1/2 by EGF and HB-EGF was independent of PKC and metalloprotease activity. The signaling characteristics of HB-EGF closely resembled those of GnRH and EGF in terms of the phosphorylation of EGF-R, Shc, ERK1/2, and RSK-1 as well as the nuclear translocation of RSK-1. However, neither the selective Src kinase inhibitor PP2 nor the overexpression of negative regulatory Src kinase and dominant negative Pyk2 had any effect on HB-EGF-induced responses. In contrast to GT1-7 cells, human embryonic kidney 293 cells expressing the GnRH-R did not exhibit metalloprotease induction and EGF-R transactivation during GnRH stimulation. These data indicate that the GnRH-induced transactivation of the EGF-R and the subsequent ERK1/2 phosphorylation result from ectodomain shedding of HBEGF through PKC-dependent activation of metalloprotease(s) in neuronal GT1-7 cells.
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PMID:Neuropeptide-induced transactivation of a neuronal epidermal growth factor receptor is mediated by metalloprotease-dependent formation of heparin-binding epidermal growth factor. 1457 93

Enhanced production of reactive oxygen species (ROS) such as H(2)O(2) and a failure in ROS removal by scavenging systems are hallmarks of several cardiovascular diseases such as atherosclerosis and hypertension. ROS act as second messengers that play a prominent role in intracellular signaling and cellular function. In vascular smooth muscle cells (VSMCs), a vascular pathogen, angiotensin II, appears to initiate growth-promoting signal transduction through ROS-sensitive tyrosine kinases. However, the precise mechanisms by which tyrosine kinases are activated by ROS remain unclear. In this review, the current knowledge that suggests how certain tyrosine kinases are activated by ROS, along with their functional significance in VSMCs, will be discussed. Recent findings suggest that transactivation of the epidermal growth factor receptor by ROS requires metalloprotease-dependent heparin-binding epidermal growth factor-like growth factor production, whereas other ROS-sensitive tyrosine kinases such as PYK2, JAK2, and platelet-derived growth factor receptor require activation of protein kinase C-delta. Each of these ROS-sensitive kinases could mediate specific signaling critical for pathophysiological responses. Detailed analysis of the mechanism of cross-talk and the downstream function of these various tyrosine kinases will yield new therapeutic interventions for cardiovascular disease.
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PMID:Activation of tyrosine kinases by reactive oxygen species in vascular smooth muscle cells: significance and involvement of EGF receptor transactivation by angiotensin II. 1458 50

In addition to their inhibitory effects, cannabinoids also exert stimulatory activity which can be detected at the cellular level. In a previous study, we demonstrated a stimulatory effect of the synthetic cannabinoid receptor agonist desacetyllevonantradol (DALN) on Ca(2+) flux into N18TG2 neuroblastoma cells, and suggested a dual mechanism: one pathway mediated by PKA and the other one by protein kinase C (PKC). Here we studied the PKC-mediated effect of DALN on Ca(2+) influx. The stimulatory effect of DALN on Ca(2+) influx was partially blocked by the PKC inhibitor chelerythrine, by the metalloprotease inhibitor o-phenanthroline and by the MEK (mitogen-activated protein-kinase kinase, MAPK kinase) inhibitor PD98059. Immunobloting of ERK1/2 MAPK demonstrated phosphorylation by DALN, and indicated the involvement of vascular endothelial growth factor (VEGF) receptor tyrosin kinases (RTKs) in MAPK activation as it was blocked by oxindole-1. Transactivation of the VEGFR-MAPK cascade by DALN involved CB1 cannabinoid receptors coupled to Gi/Go GTP-binding proteins as it was blocked by SR141716A and by pertussis toxin (PTX). The pharmacological implications of this novel mechanism of cannabinoid activity are discussed.
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PMID:The involvement of VEGF receptors and MAPK in the cannabinoid potentiation of Ca2+ flux into N18TG2 neuroblastoma cells. 1474 3

Megalin, a member of the low density lipoprotein receptor gene family, is required for efficient protein absorption in the proximal tubule. Recent studies have shown that the low density lipoprotein receptor-related protein, another member of this gene family, is proteolytically processed by gamma-secretase implying a role for low density lipoprotein receptor-related protein in a Notchlike signaling pathway. This pathway has been shown to involve: 1) metalloprotease-mediated ectodomain shedding and gamma-secretase-mediated intramembrane proteolysis of some receptors. Experiments were performed to determine whether megalin undergoes similar processing. By immunocytochemistry, immunoblotting, and a fluorogenic enzyme assay presenilin-1 (required for gamma-secretase activity) and gamma-secretase activity were found in the brush border of proximal kidney tubules where megalin is localized. Using a fluorogenic peptide containing an amyloid precursor protein gamma-secretase cleavage site and Compound E, a specific gamma-secretase inhibitor, we found high levels of gamma-secretase activity in renal brush border membrane vesicles. Immunoblotting analysis of renal microsomes and opossum kidney proximal tubule (OKP) cells using antibodies directed to the cytosolic domain of megalin showed a 35-40-kDa, membrane-associated, carboxyl-terminal fragment of megalin (MCTF). When cells were incubated with 200 nm phorbol 12-myristate 13-acetate, the appearance of the MCTF increased 2.5-fold and was blocked by metalloprotease inhibitors. When the cells were incubated with gamma-secretase inhibitor Compound E, it caused a 2-fold increase in MCTF. Finally, incubating the cells with 1 microm vitamin D-binding protein resulted in a 25% increase in the appearance of the MCTF. In summary, the MCTF is produced by protein kinase C regulated, metalloprotease-mediated ectodomain shedding and is the substrate for gamma-secretase. We postulate that the enzymatic processing of megalin represents part of a novel ligand-dependent signaling pathway in the proximal tubule that links receptor-mediated endocytosis with cell signaling.
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PMID:Linking receptor-mediated endocytosis and cell signaling: evidence for regulated intramembrane proteolysis of megalin in proximal tubule. 1518 Sep 87


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