Effect of a peptide inhibitor of protein kinase C on G-protein-mediated increase in myofilament Ca(2+)-sensitivity in rabbit arterial skinned muscle.
1. To investigate the role of protein kinase C in the increase mediated by guanosine 5'-triphosphate (GTP)-binding proteins (G-proteins) in the sensitivity of the contractile proteins to Ca2+ in vascular smooth muscle, the effect of a novel peptide inhibitor of protein kinase C (PKC19-36) on Ca(2+)-induced contraction and myosin light chain (MLC) phosphorylation was studied in the presence and absence of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S) in beta-escin-skinned smooth muscle strips of rabbit mesenteric artery. For comparison, the effects were also observed of PKC19-36 on the action of phorbol 12,13-dibutylate (PDBu, an activator of PKC) on the two Ca(2+)-induced responses. 2. In beta-escin-skinned strips treated with ionomycin, Ca2+ (0.1-3 microM) concentration-dependently produced contraction in parallel with an increase in MLC-phosphorylation. GTP gamma S (10 microM) and PDBu (0.1 microM) each shifted both the Ca(2+)-force and Ca(2+)-MLC-phosphorylation relationships to the left without a significant change in either maximum response. The relationship between force and MLC-phosphorylation was not modified by either GTP gamma S or PDBu, indicating that the sensitivity of MLC-phosphorylation to Ca2+ is enhanced by both GTP gamma S and PDBu. 3. PKC19-36 itself modified neither the contraction nor MLC-phosphorylation induced by Ca2+ but it did block the PDBu-induced enhancement of these two Ca(2+)-induced responses. By contrast, PKC19-36 did not modify the GTP gamma S-induced enhancement of the two Ca(2+)-induced responses. Guanosine 5'-O-(2-thiodiphosphate) (GDP Beta S) attenuated the GTP gamma S-induced enhancement of the Ca2+-induced contraction.4. These results suggest that GTP gamma S increases Ca2+-induced MLC-phosphorylation through the activation of a PKC-independent mechanism and thus causes an increase in the sensitivity of the contractile proteins to Ca2+ in Beta-escin-skinned smooth muscle of rabbit mesenteric artery.
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
T
T
Itoh
A
A
Suzuki
Y
Y
Watanabe
D008841:Actin Cytoskeleton / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology*; D004928:Escin / Q000737:chemistry; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology*; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000494:pharmacology*; D011817:Rabbits
D010446:Peptide Fragments; C072093:protein kinase C (19-36); D015240:Phorbol 12,13-Dibutyrate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D004928:Escin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D009218:Myosins; D002118:Calcium