title: Rho GTPase signaling modulates cell shape and contractile phenotype in an isoactin-specific manner.
abstract: Rho family small GTPases (Rho, Rac, and Cdc42) play an important role in cell motility, adhesion, and cell division by signaling reorganization of the actin cytoskeleton. Here, we report an isoactin-specific, Rho GTPase-dependent signaling cascade in cells simultaneously expressing smooth muscle and nonmuscle actin isoforms. We transfected primary cultures of microvascular pericytes, cells related to vascular smooth muscle cells, with various Rho-related and Rho-specific expression plasmids. Overexpression of dominant positive Rho resulted in the formation of nonmuscle actin-containing stress fibers. At the same time, alpha-vascular smooth muscle actin (alphaVSMactin) containing stress fibers were disassembled, resulting in a dramatic reduction in cell size. Rho activation also yielded a disassembly of smooth muscle myosin and nonmuscle myosin from stress fibers. Overexpression of wild-type Rho had similar but less dramatic effects. In contrast, dominant negative Rho and C3 exotransferase or dominant positive Rac and Cdc42 expression failed to alter the actin cytoskeleton in an isoform-specific manner. The loss of smooth muscle contractile protein isoforms in pericyte stress fibers, together with a concomitant decrease in cell size, suggests that Rho activation influences "contractile" phenotype in an isoactin-specific manner. This, in turn, should yield significant alteration in microvascular remodeling during developmental and pathologic angiogenesis.
authors.affiliation: Department of Physiology, Tufts University School of Medicine, 136 Harrison Avenue, Boston, MA 02111, USA. alexey.kolyada@tufts.edu
authors.forename: Alexey Y
authors.initials: AY
authors.lastname: Kolyada
authors.forename: Kathleen N
authors.initials: KN
authors.lastname: Riley
authors.forename: Ira M
authors.initials: IM
authors.lastname: Herman
mesh_terms: D000199:Actins / Q000502:physiology*; D000818:Animals; D002417:Cattle; D002465:Cell Movement / Q000502:physiology*; D048429:Cell Size / Q000502:physiology; D002478:Cells, Cultured; D009154:Mutation; D020286:Pericytes / Q000166:cytology / Q000502:physiology*; D010641:Phenotype; D020033:Protein Isoforms / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000502:physiology*
chemical_list: D000199:Actins; D020033:Protein Isoforms; D020741:rho GTP-Binding Proteins