Developmentally regulated expression of calponin isoforms and the effect of h2-calponin on cell proliferation.
h2-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.
Hossain
M Moazzem
MM
Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-4970, USA.
Hwang
Daw-Yang
DY
Huang
Qi-Quan
QQ
Sasaki
Yasuharu
Y
Jin
Jian-Ping
JP
D000818:Animals; D002135:Calcium-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D002455:Cell Division / Q000235:genetics; D002461:Cell Line, Transformed; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006131:Growth Inhibitors / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008840:Microfilament Proteins; D009130:Muscle, Smooth / Q000166:cytology* / Q000378:metabolism*; D011247:Pregnancy; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D011817:Rabbits; D013270:Stomach / Q000166:cytology; D014162:Transfection; D014599:Uterus / Q000166:cytology / Q000378:metabolism; D000096985:Calponins
D002135:Calcium-Binding Proteins; D006131:Growth Inhibitors; D008840:Microfilament Proteins; D020033:Protein Isoforms; D000096985:Calponins