title: Interactive role of protein phosphatase 2A and protein kinase Calpha in the stretch-induced triphosphorylation of myosin light chain in canine cerebral artery.
abstract: The interactive role of protein kinase C (PKC) isoforms and protein phosphatase 2A (PP2A) in the mechanisms underlying the gradual reduction in stretch-induced contraction through triphosphorylation of 20-kDa myosin light chain (MLC(20)) was investigated in the canine basilar artery. In the presence of 5 mM tetraethylammonium, stretching at a rate of 1 mm/s from the initial length (L(i)) to 1.5 L(i) produced a contraction. Maintaining the stretched state for 15 min (15-min stretch) produced triphosphorylation of MLC(20 )at Ser-19, Thr-18 and Thr-9, and a gradual reduction in the contraction, both of which were reversed by Gö6976 (1 microM), an inhibitor of conventional PKC. The 15-min stretch increased PKCalpha activity whereas it decreased PP2A activity, both of which were blocked by Y-27632, an inhibitor of rho kinase. Okadaic acid (OA; 1 microM), a PP2A inhibitor, also produced triphosphorylation of MLC(20) at the same amino acid residues and activated PKCalpha, which was inhibited by Gö6976. Stretching and OA increased phosphorylation of 17-kDa PKC-potentiated inhibitory phosphoprotein (CPI-17), and this phosphorylation was inhibited by Gö6976. The present results suggest that activation of PKCalpha mediated by an inhibitor of PP2A is involved in the stretch-induced triphosphorylation of MLC(20), and that this triphosphorylation counteracts the stretch-induced contraction.
authors.affiliation: Department of Pharmacology, School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan. obara@u-shizuoka-ken.ac.jp
authors.forename: Kazuo
authors.initials: K
authors.lastname: Obara
authors.forename: Ayako
authors.initials: A
authors.lastname: Mitate
authors.forename: Kayo
authors.initials: K
authors.lastname: Nozawa
authors.forename: Makiko
authors.initials: M
authors.lastname: Watanabe
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Ito
authors.forename: Koichi
authors.initials: K
authors.lastname: Nakayama
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D001488:Basilar Artery / Q000187:drug effects / Q000201:enzymology*; D002227:Carbazoles / Q000494:pharmacology; D002536:Cerebral Arteries / Q000187:drug effects / Q000201:enzymology*; D004285:Dogs; D004789:Enzyme Activation; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D018994:Myosin Light Chains / Q000378:metabolism*; D019319:Okadaic Acid / Q000494:pharmacology; D010766:Phosphorylation; D011311:Pressoreceptors / Q000378:metabolism*; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D013997:Time Factors; D014661:Vasoconstriction / Q000187:drug effects; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000577:Amides; D002227:Carbazoles; D018994:Myosin Light Chains; D047428:Protein Kinase Inhibitors; D011725:Pyridines; C081021:Go 6976; C108830:Y 27632; D019319:Okadaic Acid; D054460:rho-Associated Kinases; D051571:Protein Kinase C-alpha; D054648:Protein Phosphatase 2