Effects of h1-calponin ablation on the contractile properties of bladder versus vascular smooth muscle in mice lacking SM-B myosin.
The functional significance of smooth muscle-specific h1-calponin up-regulation in the smooth muscle contractility of SM-B null mice was studied by generating double knockout mice lacking both h1-calponin and SM-B myosin. The double knockout mice appear healthy, reproduce well and do not show any smooth muscle pathology. Loss of h1-calponin in the SM-B null mice bladder resulted in increased maximal shortening velocity (V(max)) and steady-state force generation. The force dilatation pressure, which was decreased in the SM-B null mesenteric vessels, was restored to wild-type levels in the double knockout vessels. In contrast, the half-time to maximal constriction was significantly increased in the double knockout vessels similar to that of SM-B null mice and indicating decreased shortening velocity in the double knockout vessels. Biochemical analyses showed that there is a significant reduction in smooth muscle alpha-actin levels, whereas h-caldesmon levels are increased in the double knockout bladder and mesenteric vessels, suggesting that these changes may also partly contribute to the altered contractile function. Taken together, our studies suggest that up-regulation of h1-calponin in the SM-B null mice may be necessary to maintain a reduced level of cross-bridge cycling over time in the absence of SM-B myosin and play an important role in regulating the smooth muscle contraction.
Babu
Gopal J
GJ
Department of Physiology and Cell Biology, The Ohio State University College of Medicine and Public Health, 304 Hamilton Hall, 1645 Neil Avenue, Columbus, OH 43210, USA. babu.10@osu.edu
Celia
Gerard
G
Rhee
Albert Y
AY
Yamamura
Hisako
H
Takahashi
Katsuhito
K
Brozovich
Frank V
FV
Osol
George
G
Periasamy
Muthu
M
D000199:Actins / Q000037:antagonists & inhibitors; D000818:Animals; D002135:Calcium-Binding Proteins / Q000172:deficiency*; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008638:Mesenteric Arteries / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology; D051379:Mice; D018345:Mice, Knockout; D008840:Microfilament Proteins / Q000172:deficiency*; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000033:anatomy & histology / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000033:anatomy & histology / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D018994:Myosin Light Chains / Q000378:metabolism; D024501:Nonmuscle Myosin Type IIB / Q000172:deficiency*; D020033:Protein Isoforms / Q000378:metabolism; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000378:metabolism / Q000502:physiology*; D014661:Vasoconstriction / Q000502:physiology*; D000096985:Calponins
D000199:Actins; D002135:Calcium-Binding Proteins; D002148:Calmodulin-Binding Proteins; D008840:Microfilament Proteins; D018995:Myosin Heavy Chains; D018994:Myosin Light Chains; D024501:Nonmuscle Myosin Type IIB; D020033:Protein Isoforms; D000096985:Calponins