Differential effects of putative protein kinase C inhibitors on contraction of rat aortic smooth muscle

We investigated effects of three kinds of putative protein kinase C (PKC) inhibitors, calphostin C, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7), and stauro-sporine, on aortic muscle contractions induced by KCl, phenylephrine, 12-O-tetradecanoylphorbol-13-acetate (TPA), and phorbol 12, 13-dibutyrate (PDBu). Calphostin C noncompetitively inhibited TPA-induced contractions in a concentration-dependent manner. At 10(-6) M, calphostin C completely abolished responses to TPA and also effectively inhibited PDBu-induced contractions. Such a concentration of calphostin C had no effect on KCl-induced contractions but decreased the maximal tension of phenylephrine-induced response curve by 35.3 +/- 6.6% H-7 (10(-5) M had little effect on TPA-induced contraction but significantly inhibited contractile responses to phenylephrine and KCl. Staurosporine (10(-8) M, 3 x 10(-8) M) inhibited contractile responses to KCl, phenylephrine, and TPA. We suggest that staurosporine and H-7, which are known to act on the catalytic domain of PKC carrying high degree of sequence homology with other protein kinases, are relatively nonselective for PKC. On the other hand, calphostin C acting on the regulatory domain of PKC, which is distinct from other protein kinases, may serve as a relatively more selective PKC inhibitor.

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The Acidic Region and Conserved Putative Protein Kinase C Phosphorylation Site in Nef Are Important for SIV Replication in Rhesus Macaques

Virology ◽

10.1006/viro.1999.9645 ◽

1999 ◽

Vol 257 (1) ◽

pp. 138-155 ◽

Cited By ~ 14

Author(s):

Silke Carl ◽

A.John Iafrate ◽

Sabine M. Lang ◽

Christiane Stahl-Hennig ◽

Eva M. Kuhn ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Rhesus Macaques ◽

Phosphorylation Site ◽

Putative Protein ◽

Kinase C ◽

Acidic Region ◽

Putative Protein Kinase

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The role of protein kinase C in GH secretion induced by GH-releasing factor and GH-releasing peptides in cultured ovine somatotrophs

Journal of Endocrinology ◽

10.1677/joe.0.1540219 ◽

1997 ◽

Vol 154 (2) ◽

pp. 219-230 ◽

Cited By ~ 26

Author(s):

D Wu ◽

I J Clarke ◽

C Chen

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Dependent Manner ◽

Adenylyl Cyclase Activity ◽

Down Regulation ◽

Gh Secretion ◽

Calphostin C ◽

Kinase C ◽

Pka Pathway

Abstract The involvement of protein kinase C (PKC) in the action of GH-releasing factor (GRF) and synthetic GH-releasing peptides (GHRP-2 and GHRP-6) was investigated in ovine somatotrophs in primary culture. In partially purified sheep somatotrophs, GRF and GHRP-2 caused translocation of PKC activity from the cytosol to the cell membranes and caused GH release in a dose- and time-dependent manner. GHRP-6 did not cause PKC translocation. The PKC inhibitors, calphostin C, staurosporine and chelerythrine, partially reduced GH release in response to GRF and GHRP-2 at doses which selectively inhibit PKC activity. These inhibitors totally abolished GH release caused by phorbol 12-myristate 13-acetate (PMA). Down-regulation of PKC by the treatment of cells with phorbol 12,13-dibutyrate for 16 h caused a significant (P<0·001) reduction in total PKC activity and totally abolished PKC translocation in response to a challenge with GRF, GHRP-2 or PMA. In addition, down-regulation abolished GH release in response to GRF, GHRP-2 or GHRP-6. Treatment of cells with H89, a selective PKA inhibitor, totally blocked GH release caused by either GRF or GHRP-2 and partially reduced PMA-induced GH release. H89 had no effect on PKC translocation caused by GRF, GHRP-2 or PMA and did not affect GH release caused by GHRP-6. These data suggest that GHRP-2 and GRF activate PKC in addition to stimulating adenylyl cyclase activity. Although the cAMP–protein kinase A (PKA) pathway is the major signalling pathway employed by GRF and GHRP-2, the activation of PKC may potentiate signalling via the cAMP–PKA pathway in ovine GH secretion. Importantly, the effect of PMA in increasing the secretion of GH from ovine somatotrophs is effected, in part, by up-regulation of the cAMP–PKA pathway. We conclude that there is cross-talk between the PKC pathway and the cAMP–PKA pathway in ovine somatotrophs during the action of GRF or GHRP. Journal of Endocrinology (1997) 154, 219–230

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