title: CPI-17-deficient smooth muscle of chicken.
abstract: Ca(2+) sensitivity of arterial contractility is governed by regulating myosin phosphatase activity in response to agonist stimuli. CPI-17, a myosin phosphatase inhibitor phosphoprotein, is phosphorylated concomitantly with agonist-induced contractile Ca(2+) sensitization in mammalian artery. CPI-17 has not been detected in chicken artery, but is readily detectable in pigeon artery. To evaluate a role of CPI-17, we compared contractility of the arteries of 'CPI-17-deficient' chicken with those of CPI-17-rich rabbit and pigeon, and studied the effect of CPI-17-reconstitution in chicken artery. Other major regulatory/contractile proteins for Ca(2+) sensitization are expressed in both chicken and rabbit arteries. Agonists, such as an alpha(1)-agonist and endothelin-1, produced significant contraction in arteries of all species under physiological Ca(2+)-containing conditions. Depletion of Ca(2+) abolished these contractions in chicken but partially inhibited them in rabbit and pigeon arteries. Unlike CPI-17-rich tissues, chicken arteries exerted little Ca(2+) sensitization in response to alpha(1)-agonist or endothelin-1. GTPgammaS produced a slight Ca(2+) sensitizing effect in chicken artery, but this was significantly smaller compared with CPI-17-rich tissues. A PKC activator (PDBu) did not generate but rather reduced a contraction in both intact and alpha-toxin-permeabilized chicken artery in contrast to a large contraction in CPI-17-rich arteries. Myosin light chain phosphorylation was reduced by PDBu in chicken but elevated in rabbit artery. Addition of recombinant CPI-17 into beta-escin-permeabilized chicken artery restored PDBu-induced and enhanced GTPgammaS-induced Ca(2+) sensitization. Thus, CPI-17 is essential for G protein/PKC-mediated Ca(2+) sensitization in smooth muscle.
authors.affiliation: Boston Biomedical Research Institute, 64 Grove Street, Watertown, MA 02472, USA. kitazawa@bbri.org
authors.forename: Toshio
authors.initials: T
authors.lastname: Kitazawa
authors.forename: Atsuko N
authors.initials: AN
authors.lastname: Polzin
authors.forename: Masumi
authors.initials: M
authors.lastname: Eto
mesh_terms: D000818:Animals; D001011:Aorta; D002118:Calcium / Q000378:metabolism*; D002645:Chickens / Q000378:metabolism / Q000502:physiology*; D010856:Columbidae; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009124:Muscle Proteins / Q000096:biosynthesis / Q000172:deficiency* / Q000276:immunology; D009130:Muscle, Smooth / Q000201:enzymology / Q000502:physiology*; D018994:Myosin Light Chains / Q000378:metabolism; D043263:Myosin-Light-Chain Phosphatase / Q000037:antagonists & inhibitors*; D010750:Phosphoproteins / Q000096:biosynthesis / Q000172:deficiency* / Q000276:immunology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011817:Rabbits; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000494:pharmacology
chemical_list: C491521:CPI-17 protein, Oryctolagus cuniculus; D009124:Muscle Proteins; D018994:Myosin Light Chains; D010750:Phosphoproteins; D011994:Recombinant Proteins; D011493:Protein Kinase C; D043263:Myosin-Light-Chain Phosphatase; D019204:GTP-Binding Proteins; D002118:Calcium