title: Relative importance of βcyto- and γcyto-actin in primary mouse embryonic fibroblasts.
abstract: The highly homologous β (βcyto) and γ (γcyto) cytoplasmic actins are hypothesized to carry out both redundant and unique essential functions, but studies using targeted gene knockout and siRNA-mediated transcript knockdown to examine βcyto- and γcyto-isoform--specific functions in various cell types have yielded conflicting data. Here we quantitatively characterized actin transcript and protein levels, as well as cellular phenotypes, in both gene- and transcript-targeted primary mouse embryonic fibroblasts. We found that the smooth muscle αsm-actin isoform was the dominantly expressed actin isoform in WT primary fibroblasts and was also the most dramatically up-regulated in primary βcyto- or β/γcyto-actin double-knockout fibroblasts. Gene targeting of βcyto-actin, but not γcyto-actin, led to greatly decreased cell proliferation, decreased levels of cellular ATP, and increased serum response factor signaling in primary fibroblasts, whereas immortalization induced by SV40 large T antigen supported fibroblast proliferation in the absence of βcyto-actin. Consistent with in vivo gene-targeting studies in mice, both gene- and transcript-targeting approaches demonstrate that the loss of βcyto-actin protein is more disruptive to primary fibroblast function than is the loss of γcyto-actin.
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Xiaobai
authors.initials: X
authors.lastname: Patrinostro
authors.affiliation: Program in Molecular, Cellular, Developmental Biology, and Genetics, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Allison R
authors.initials: AR
authors.lastname: O'Rourke
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Chamberlain
authors.affiliation: Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455.
authors.forename: Branden S
authors.initials: BS
authors.lastname: Moriarity
authors.affiliation: Department of Biology, Indiana University-Purdue University Indianapolis, Indianapolis, IN 46022.
authors.forename: Benjamin J
authors.initials: BJ
authors.lastname: Perrin
authors.affiliation: Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455 jervasti@umn.edu.|Program in Molecular, Cellular, Developmental Biology, and Genetics, University of Minnesota, Minneapolis, MN 55455.
authors.forename: James M
authors.initials: JM
authors.lastname: Ervasti
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D002465:Cell Movement / Q000235:genetics / Q000502:physiology; D049109:Cell Proliferation; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism / Q000502:physiology; D005347:Fibroblasts / Q000378:metabolism; D055786:Gene Knockout Techniques; D051379:Mice / Q000196:embryology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D000199:Actins; D020033:Protein Isoforms