Developmentally regulated expression of calponin isoforms and the effect of h2-calponin on cell proliferation

Abstract

. Developmentally regulated expression of calponin isoforms and the effect of h2-calponin on cell proliferation. Am J Physiol Cell Physiol 284: C156-C167, 2003. First published September 4, 2002 10.1152/ajpcell.00233.2002-Calponin is found in both smooth muscle and nonmuscle cells, and its function remains to be established. Western blots with specific monoclonal antibodies detected significant expression of h2-calponin in the growing embryonic stomach and urinary bladder and the early pregnant uterus. Although the expression of h1-calponin is upregulated in the stomach and bladder during postnatal development, the expression of h2-calponin is decreased to low levels in quiescent smooth muscle cells. To investigate a hypothesis that h2-calponin regulates the function of the actin cytoskeleton during cytokinesis, a smooth muscle-originated cell line (SM3) lacking calponin was transfected to express either sense or antisense h2-calponin cDNA and the effects on the rates of cell proliferation were examined. Both stable and transient sense cDNA-transfected cells had a significantly decreased proliferation rate compared with the antisense cDNA-transfected or nontransfected cells. Immunofluorescence microscopy showed that the force-expressed h2-calponin was associated with actin-tropomyosin microfilaments. The number of binuclear cells was significantly greater in the sense cDNA-transfected culture, in which h2-calponin was concentrated in a nuclear ring structure formed by actin filaments. The results suggest that h2-calponin may regulate cytokinesis by inhibiting the activity of the actin cytoskeleton. smooth muscle development; cytokinesis; tropomyosin; actin cytoskeleton; monoclonal antibody; transfective expression CALPONIN IS A FAMILY of actin filament-associated proteins. Three isoforms of calponin, h1 (9, 33, 43), h2 (42), and acidic (1, 45), have been identified. Isoelectric points (pIs) of these three calponin isoforms show that h1-calponin is basic (pI ϭ 8.5-9.2), h2-calponin is neutral (pI ϭ 7.2-7

Mutant p53 reactivation by PRIMA-1MET induces multiple signaling pathways converging on apoptosis

“…Ectopic expression of the WASP-binding protein, WIRE, causes actin cytoskeleton redistribution and actin depolymerization (Hossain et al, 2003). Overexpression of supervillin, an F-actin-binding protein, results in increased levels of F-actin (Wulfkuhle et al, 1999).…”

Serum response factor is an essential transcription factor in megakaryocytic maturation

“…It has been ascribed a role as a sensor of mechanical tension resulting in modification of the actin cytoskeleton 50 whereby it may control cell motility and cytokinesis. 51,52 Forced overexpression of calponin in cultured smooth muscle cells and fibroblasts transfected with viral promoterdirected expression vectors inhibited the rate of cell proliferation and the completion of cell division. 52 The function of calponin and coronin, specifically megakaryopoiesis, platelet formation and function, remains to be shown.…”

Actin stress fibers – assembly, dynamics and biological roles

“…The most extensively studied isoform is calponin-1 (also known as calponin h1), which is expressed in smooth muscle cells and is involved in the regulation of contractility (Winder et al, 1998). The other calponin isoforms, -2 and -3 (h2 and h3, respectively), are found in many non-muscle and muscle cells (Draeger et al, 1991;Hossain et al, 2003). In addition to regulating muscle contraction, calponins have been suggested to crosslink and stabilize actin-based structures, as well as to regulate cell motility (Leinweber et al, 1999b;Danninger and Gimona, 2000).…”