Heterogeneous distribution of isoactins in cultured vascular smooth muscle cells does not reflect segregation of contractile and cytoskeletal domains.
We have previously demonstrated that alpha-smooth muscle (alpha-SM) actin is predominantly distributed in the central region and beta-non-muscle (beta-NM) actin in the periphery of cultured rabbit aortic smooth muscle cells (SMCs). To determine whether this reflects a special form of segregation of contractile and cytoskeletal components in SMCs, this study systematically investigated the distribution relationship of structural proteins using high-resolution confocal laser scanning fluorescent microscopy. Not only isoactins but also smooth muscle myosin heavy chain, alpha-actinin, vinculin, and vimentin were heterogeneously distributed in the cultured SMCs. The predominant distribution of beta-NM actin in the cell periphery was associated with densely distributed vinculin plaques and disrupted or striated myosin and alpha-actinin aggregates, which may reflect a process of stress fiber assembly during cell spreading and focal adhesion formation. The high-level labeling of alpha-SM actin in the central portion of stress fibers was related to continuous myosin and punctate alpha-actinin distribution, which may represent the maturation of the fibrillar structures. The findings also suggest that the stress fibers, in which actin and myosin filaments organize into sarcomere-like units with alpha-actinin-rich dense bodies analogous to Z-lines, are the contractile structures of cultured SMCs that link to the network of vimentin-containing intermediate filaments through the dense bodies and dense plaques.
Song
J
J
Centre for Research in Vascular Biology, Department of Anatomical Sciences, University of Queensland, Brisbane, Australia.
Worth
N F
NF
Rolfe
B E
BE
Campbell
G R
GR
Campbell
J H
JH
D000185:Actinin / Q000378:metabolism; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001011:Aorta / Q000166:cytology; D002478:Cells, Cultured; D003599:Cytoskeleton / Q000378:metabolism; D005453:Fluorescence; D018613:Microscopy, Confocal; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D011817:Rabbits; D014746:Vimentin / Q000378:metabolism; D016596:Vinculin / Q000378:metabolism
D000199:Actins; D020033:Protein Isoforms; D014746:Vimentin; D000185:Actinin; D016596:Vinculin; D018995:Myosin Heavy Chains