The distribution of contractile and cytoskeletal proteins in smooth muscle has been mapped by immunocytochemical methods, with special reference to the localization of the actin-binding protein, filamin. Immunolabeling of ultrathin sections of polyvinylalcohol-embedded smooth muscle distinguished two domains in the smooth muscle cell: (a) actomyosin domains, made up of continuous longitudinal arrays of actin and myosin filaments, and (b) longitudinal, fibrillar, intermediate filament domains, free of myosin but containing actin and alpha-actinin-rich dense bodies. Filamin was found to be localized specifically in the latter intermediate filament-actin domains, but was excluded from the core of the dense bodies. Filamin was also localized close to the cell border at the inner surface of the plasmalemma-associated plaques. In isolated cells the surface filamin label showed a rib-like distribution similar to that displayed by vinculin. It is speculated that the two domains distinguished in these studies may reflect the existence of two functionally distinct systems: an actomyosin system required for contraction and an intermediate filament-actin system, with associated gelation proteins, that is responsible, at least in part, for the slow relaxation and tone peculiar to smooth muscle.
Article| January 01 1986
Localization of filamin in smooth muscle.
J V Small
D O Fürst
J De Mey
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1986) 102 (1): 210–220.
J V Small, D O Fürst, J De Mey; Localization of filamin in smooth muscle.. J Cell Biol 1 January 1986; 102 (1): 210–220. doi: https://doi.org/10.1083/jcb.102.1.210
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