Reversal of caldesmon function by anti-caldesmon antibodies confirms its role in the calcium regulation of vascular smooth muscle thin filaments.
Direct evidence that caldesmon is the Ca2+-regulated inhibitory component of native smooth muscle thin filaments is provided by studies using caldesmon-specific antibodies as antagonists. The antibodies reverse caldesmon inhibition of actomyosin ATPase and abolish Ca2+-regulation of native aorta thin filament activation of myosin ATPase. This effect is a result of antibody binding to the caldesmon on the filament thereby inactivating it and not due to antibody-induced caldesmon dissociation from the filament. The antibodies, however, neutralise caldesmon only in systems using skeletal muscle myosin and not in those using smooth muscle myosin; this implies that smooth muscle myosin prevents appropriate antibody binding to caldesmon perhaps because smooth muscle myosin binds to caldesmon thus preventing access of antibody to antigenic sites.
Marston
S B
SB
Cardiothoracic Institute, London, UK.
Redwood
C S
CS
Lehman
W
W
D008841:Actin Cytoskeleton / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D000199:Actins / Q000502:physiology; D000818:Animals; D001666:Binding Sites, Antibody; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors; D002148:Calmodulin-Binding Proteins / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D003599:Cytoskeleton / Q000502:physiology*; D007074:Immunoglobulin G / Q000378:metabolism / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D014335:Tropomyosin / Q000502:physiology
D000199:Actins; D002148:Calmodulin-Binding Proteins; D007074:Immunoglobulin G; D014335:Tropomyosin; D017301:Ca(2+) Mg(2+)-ATPase