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CPI‐17‐deficient smooth muscle of chicken
Author(s) -
Kitazawa Toshio,
Polzin Atsuko N.,
Eto Masumi
Publication year - 2004
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2004.064543
Subject(s) - chemistry , microbiology and biotechnology , medicine , anatomy , biology
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 α 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 α 1 ‐agonist or endothelin‐1. GTPγS 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 α‐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 β‐escin‐permeabilized chicken artery restored PDBu‐induced and enhanced GTPγS‐induced Ca 2+ sensitization. Thus, CPI‐17 is essential for G protein/PKC‐mediated Ca 2+ sensitization in smooth muscle.