Calponin repeats regulate actin filament stability and formation of podosomes in smooth muscle cells.
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 stabilization and dynamics of the actin cytoskeleton in mammalian smooth muscle. We provide evidence for the existence of two functionally distinct actin filament populations and introduce a molecular mechanism for the stabilization of the actin cytoskeleton by the unique actin-binding interface formed by calponin family-specific CLIK23 repeats.
Gimona
Mario
M
Institute of Molecular Biology, Department of Cell Biology, Austrian Academy of Sciences, A-5020 Salzburg, Austria. mgimona@server1.imolbio.oeaw.ac.at
Kaverina
Irina
I
Resch
Guenter P
GP
Vignal
Emmanuel
E
Burgstaller
Gerald
G
D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D008840:Microfilament Proteins; D008854:Microscopy, Electron; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D015388:Organelles / Q000378:metabolism; D051381:Rats; D000096985:Calponins
D000199:Actins; D002135:Calcium-Binding Proteins; D008840:Microfilament Proteins; D000096985:Calponins