Blebbistatin, a myosin II inhibitor, suppresses contraction and disrupts contractile filaments organization of skinned taenia cecum from guinea pig.
To explore the precise mechanisms of the inhibitory effects of blebbistatin, a potent inhibitor of myosin II, on smooth muscle contraction, we studied the blebbistatin effects on the mechanical properties and the structure of contractile filaments of skinned (cell membrane permeabilized) preparations from guinea pig taenia cecum. Blebbistatin at 10 microM or higher suppressed Ca(2+)-induced tension development at any given Ca(2+) concentration but had little effects on the Ca(2+)-induced myosin light chain phosphorylation. Blebbistatin also suppressed the 10 and 2.75 mM Mg(2+)-induced, "myosin light chain phosphorylation-independent" tension development at more than 10 microM. Furthermore, blebbistatin induced conformational change of smooth muscle myosin (SMM) and disrupted arrangement of SMM and thin filaments, resulting in inhibition of actin-SMM interaction irrespective of activation with Ca(2+). In addition, blebbistatin partially inhibited Mg(2+)-ATPase activity of native actomyosin from guinea pig taenia cecum at around 10 microM. These results suggested that blebbistatin suppressed skinned smooth muscle contraction through disruption of structure of SMM by the agent.
Watanabe
Masaru
M
Dept. of Physiology, Tokyo Medical Univ., Japan. masaru@tokyo-med.ac.jp
Yumoto
Masatoshi
M
Tanaka
Hideyuki
H
Wang
Hon Hui
HH
Katayama
Takeshi
T
Yoshiyama
Shinji
S
Black
Jason
J
Thatcher
Sean E
SE
Kohama
Kazuhiro
K
D008841:Actin Cytoskeleton; D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002432:Cecum / Q000187:drug effects* / Q000502:physiology; D031541:Fluorescence Resonance Energy Transfer; D006168:Guinea Pigs; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D024462:Myosin Type II / Q000037:antagonists & inhibitors*; D021381:Protein Transport; D024745:Smooth Muscle Myosins / Q000378:metabolism
D000199:Actins; D006576:Heterocyclic Compounds, 4 or More Rings; C472645:blebbistatin; D024462:Myosin Type II; D024745:Smooth Muscle Myosins; D008274:Magnesium; D002118:Calcium