title: Cytoprotection against mechanical forces delivered through beta 1 integrins requires induction of filamin A.
abstract: Cells in mechanically active environments can activate cytoprotective mechanisms to maintain membrane integrity in the face of potentially lethal applied forces. Cytoprotection may be mediated by expression of membrane-associated cytoskeletal proteins including filamin A, an actin-binding protein that increases the rigidity of the subcortical actin cytoskeleton. In this study, we tested the hypotheses that applied forces induce the expression of filamin A specifically and that this putative protective response inhibits cell death. Magnetically generated forces were applied to protein-coated magnetite beads bound to human gingival fibroblasts, cells with constitutively low basal levels of filamin A mRNA and protein. Forces applied through collagen or fibronectin, but not bovine serum albumin or poly-l-lysine-coated beads, increased mRNA and protein content of filamin A by 3-7-fold. Forces had no effect on the expression of other filamin isotypes or other cytoskeletal proteins. This effect was dependent on the duration of force and was blocked by anti-beta(1) integrin antibodies. Force also stimulated a 60% increase in expression of luciferase under the control of a filamin A promoter in transiently transfected Rat2 fibroblasts and was dependent on Sp1 transcription factor binding sites located immediately upstream of the transcription start site. Experiments with actinomycin D-treated cells showed that the increased filamin A expression after force application was due in part to prolongation of mRNA half-life. Antisense filamin oligonucleotides blocked force-induced filamin A expression and increased cell death by >2-fold above controls. The force-induced regulation of filamin A was dependent on intact actin filaments. We conclude that cells from mechanically active environments can couple diverse signals from forces applied through beta-integrins to up-regulate the production of cytoprotective cytoskeletal proteins, typified by filamin A.
authors: Canadian Institute of Health Research Group in Periodontal Physiology, Toronto, Ontario M5S 3E2, Canada.
authors: M
authors: M
authors: D'Addario
authors: P D
authors: PD
authors: Arora
authors: J
authors: J
authors: Fan
authors: B
authors: B
authors: Ganss
authors: R P
authors: RP
authors: Ellen
authors: C A
authors: CA
authors: McCulloch
mesh_terms: D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D003285:Contractile Proteins / Q000096:biosynthesis* / Q000235:genetics; D017931:DNA Primers; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D064448:Filamins; D005881:Gingiva / Q000166:cytology* / Q000378:metabolism; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D008840:Microfilament Proteins / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016329:Sp1 Transcription Factor / Q000378:metabolism
chemical_list: D003285:Contractile Proteins; D017931:DNA Primers; D064448:Filamins; D019012:Integrin beta1; D008840:Microfilament Proteins; D016329:Sp1 Transcription Factor