Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.12 (PKG)
 2,515 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The protein kinase C (PKC) family consists of a number of closely related isotypes, whose in vivo phosphorylation state is regulated in a dynamic fashion by the enzyme's activators. We have investigated here the changes in PKC phosphorylation in response to phorbol ester. Using a combination of hydroxylapatite chromatography and immunoblot with isotype-specific antibodies, we identified PKC-alpha, -delta, -epsilon, and -zeta as the isotypes expressed in PC12 cells. A two-dimensional immunoblot approach was then developed to measure the changes in the phosphorylation state of PKC-alpha before and after exposure of intact PC12 cells to phorbol ester. We found a pool of four differentially migrating PKC-alpha forms in untreated cells, which undergoes an acidic shift after phorbol ester. Furthermore, a similar shift in the two-dimensional immunoblot profile of PKC-alpha was the result of the enzyme autophosphorylation upon in vitro treatment with a combination of phosphatidylserine and phorbol ester, an effect which was enhanced by co-application of purified bovine lung cGMP-dependent protein kinase-I (PKG-I). These results demonstrate a multiple phosphorylation of PKC-alpha in untreated PC12 cells and suggest that various levels of autophosphorylation and trans-phosphorylation of this isoenzyme may occur in response to phorbol ester.
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PMID:Protein kinase C-alpha is multiply phosphorylated in response to phorbol ester stimulation of PC12 cells. 878 58

To understand the molecular mechanisms of cellular signaling of atrial natriuretic peptide (ANP), we have studied its effect on the enzymatic activity of endogenous and overexpressed protein kinase C (PKC) in rat thoracic aortic vascular smooth muscle (RTASM) cells. Angiotensin II (ANG II), endothelin-1 (ET-1), and 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated fourfold to fivefold PKC activity in PKC-alpha cDNA-transfected RTASM cells. However, pretreatment of these cells with ANP significantly inhibited the agonist-stimulated PKC activity in a dose-dependent manner. The inhibitory effect of ANP was more effective if cells were transfected with both PKC-alpha and guanylyl cyclase-A/atrial natriuretic peptide receptor (Npra) cDNAs. The agonist-stimulated PKC activity was also inhibited if RTASM cells were pretreated with cGMP analog 8-bromo-cGMP; however, the treatment of cells with a cAMP analog, dibutyryl-cAMP, did not show any discernible effect. The pretreatment of cells with Npra antagonist A-71915, significantly blocked the production of cGMP as well as the inhibitory effect of ANP on PKC activity. To further examine whether the antagonistic action of ANP and 8-bromo-cGMP on agonist-stimulated PKC activity were mediated through cGMP-dependent protein kinase (PKG), cells were treated with ANP or 8-bromo-cGMP and activators of PKC in the presence of KT-5823, a specific inhibitor of PKG. The treatment of cells with KT-5823 significantly attenuated the inhibitory effects of both ANP and 8-bromo-cGMP on agonist-stimulated PKC activity. The results from these studies provide strong evidence that ANP antagonizes the activation of PKC in RTASM cells, involving guanylyl cyclase-A receptor Npra and second messenger cGMP. Our data further support the notion that ANP acts as a negative mediator of signaling cross-talks between Npra and PKC in a cGMP-dependent manner, probably involving cGMP-dependent protein kinase in this process.
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PMID:Expression of guanylyl cyclase-A/atrial natriuretic peptide receptor blocks the activation of protein kinase C in vascular smooth muscle cells. Role of cGMP and cGMP-dependent protein kinase. 903 36

Atrial natriuretic peptide (ANP) regulates diverse physiological responses by binding to its specific guanylyl cyclase-A receptor (Npra) which synthesizes the intracellular second messenger cGMP. To understand the molecular mechanisms of cellular signaling of ANP, we have studied its effect on the enzymatic activity of overexpressed protein kinase C (PKC) in murine Leydig tumor (MA-10) cells which were transfected with PKC-alpha cDNA. Treatments with 12-O-tetradecanoylphorbol-13-acetate (TPA), angiotensin II (ANG II) and endothelin-1 (ET-1) stimulated the PKC activity by 4-5-fold in PKC-alpha cDNA transfected MA-10 cells. The pretreatment of PKC-alpha transfected cells with ANP significantly inhibited the TPA-, ANG II- and ET-1-stimulated PKC activity. The agonist-stimulated PKC activity was also inhibited in the presence of 8-bromo-cGMP, however, cAMP had no effect on stimulatory PKC activity. The exposure of cells to Npra- antagonist A71915, which blocks the production of cGMP, significantly reduced the inhibitory effect of ANP on agonist-stimulated PKC activity and accumulation of intracellular cGMP in MA-10 cells. Similarly, inhibition of cGMP-dependent protein kinase by KT5823, restored the stimulatory levels of PKC activity in the presence of ANP. These results provide direct evidence that ANP antagonizes the agonist-stimulated PKC activity in MA-10 cells, involving the specific receptor Npra, its second messenger cGMP and cGMP-dependent protein kinase. Together, these findings implicate that ANP may act as a negative mediator of 'cross-talk' between PKC-alpha and Npra signaling pathway in MA-10 cells.
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PMID:Stimulation of atrial natriuretic peptide receptor/guanylyl cyclase- A signaling pathway antagonizes the activation of protein kinase C-alpha in murine Leydig cells. 915 Feb 79