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Contractile properties and proteins of smooth muscles of a calponin knockout mouse
Author(s) -
Matthew J. D.,
Khromov A. S.,
McDuffie M. J.,
Somlyo A. V.,
Somlyo A. P.,
Taniguchi S.,
Takahashi K.
Publication year - 2000
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 - 10.1111/j.1469-7793.2000.00811.x
Subject(s) - calponin , crossbridge , actin , myosin , knockout mouse , gene isoform , tropomyosin , chemistry , endocrinology , microbiology and biotechnology , smooth muscle , medicine , biology , biophysics , biochemistry , receptor , gene
1 The role of h1‐calponin in regulating the contractile properties of smooth muscle was investigated in bladder and vas deferens of mice carrying a targeted mutation in both alleles designed to inactivate the basic calponin gene. These calponin knockout (KO) mice displayed no detectable h1‐calponin in their smooth muscles. 2 The amplitudes of Ca 2+ sensitization, force and Ca 2+ sensitivity were not significantly different in permeabilized smooth muscle of KO compared with wild‐type (WT) mice, nor were the delays in onset and half‐times of Ca 2+ sensitization, initiated by flash photolysis of caged GTPγS, different. 3 The unloaded shortening velocity ( V us ) of thiophosphorylated fibres was significantly ( P < 0.05) faster in the smooth muscle of KO than WT animals, but could be slowed by exogenous calponin to approximate WT levels; the concentration dependence of exogenous calponin slowing of V us was proportional to its actomyosin binding in situ . 4 Actin expression was reduced by 25‐50%, relative to that of myosin heavy chain, in smooth muscle of KO mice, without any change in the relative distribution of the actin isoforms. 5 We conclude that the faster V us of smooth muscle of the KO mouse is consistent with, but does not prove without further study, physiological regulation of the crossbridge cycle by calponin. Our results show no detectable role of calponin in the signal transduction of the Ca 2+ ‐sensitization pathways in smooth muscle.