Phorbol ester induces, actin cytoskeleton rearrangements in cultured vascular smooth muscle cells. Calponin and SM22 alpha are major components of differentiated smooth muscle and potential regulators of actin cytoskeleton interactions. Here we show that actin fibers decorated with h1 CaP remain stable, whereas SM22 alpha-decorated actin bundles undergo rapid reorganization into podosomes within 30 min of PDBu exposure. Ectopic expression of GFP alpha-actinin had no effect on the stability of the actin cytoskeleton and alpha-actinin was transported rapidly into PDBu-induced, podosomes. Our results demonstrate the involvement of CaP and SM22 alpha in coordinating the balance between st;iilization and dynamics of the actin cytoskeleton in mammalian smooth muscle. We provide, evidence for the existence of two functionally distinct actin filament popua lations and introduce a molecular mechanism for the stabilization of the actin cytoskeleton by the unique actin-bindinginterface formed by calponin family-specific CLIK23 repeats.
Useful keywords (using NLM MeSH Indexing)
Fluorescent Antibody Technique
Myocytes, Smooth Muscle/cytology
Myocytes, Smooth Muscle/metabolism*