title: Cell death and mechanoprotection by filamin a in connective tissues after challenge by applied tensile forces.
abstract: Cells in mechanically challenged environments must cope with high amplitude forces to maintain cell viability and tissue homeostasis. Currently, force-induced cell death and the identity of mechanoprotective factors are not defined. We examined death in cultured periodontal fibroblasts, connective tissue cells that are exposed to heavy applied forces in vivo. Static tensile forces (0.48 piconewtons/microm2 cell area) were applied through magnetite beads coated with collagen or bovine serum albumin. There was a time-dependent increase of the percentage of propidium iodide-permeable cells in force-loaded cultures incubated with collagen but not bovine serum albumin beads, indicating a role for integrins. Cells exhibited reduced mitochondrial membrane potential, increased caspase-3 activation, nuclear condensation, terminal deoxynucleotidyl transferase nick end labeling staining, and detachment from the culture dish. The caspase-3 inhibitor acetyl-Asp-Glu-Val-Asp-aldehyde reduced detachment 3-fold. There was a rapid (<10-s) decrease in plasma membrane potential after force application, which, in filamin A-deficient melanoma cells, contributed to irreversible cell depolarization. In fibroblast cultures, cells with increased permeability to propidium iodide exhibited approximately 2-fold less filamin A content than impermeable cells. Fibroblasts transfected with antisense filamin A constructs or with filamin A constructs without an actin-binding domain exhibited 2-3-fold increased proportions of dead cells relative to controls. We conclude that high amplitude forces delivered through integrins can promote apoptosis in a proportion of cells and that filamin A confers mechanoprotection by preventing membrane depolarization.
authors.affiliation: Canadian Institutes of Health Research Group in Matrix Dynamics, University of Toronto, Toronto, Ontario M5S 3E2, Canada.
authors.forename: Tiina
authors.initials: T
authors.lastname: Kainulainen
authors.forename: Alexandra
authors.initials: A
authors.lastname: Pender
authors.forename: Mario
authors.initials: M
authors.lastname: D'Addario
authors.forename: Yuanyi
authors.initials: Y
authors.lastname: Feng
authors.forename: Predrag
authors.initials: P
authors.lastname: Lekic
authors.forename: Christopher A
authors.initials: CA
authors.lastname: McCulloch
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D053148:Caspase 3; D061945:Caspase Inhibitors; D016923:Cell Death; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D003238:Connective Tissue / Q000502:physiology*; D003285:Contractile Proteins / Q000737:chemistry / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D064448:Filamins; D005434:Flow Cytometry; D005881:Gingiva / Q000166:cytology; D006801:Humans; D020287:In Situ Nick-End Labeling; D008297:Male; D008564:Membrane Potentials; D008840:Microfilament Proteins / Q000737:chemistry / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009842:Oligopeptides / Q000494:pharmacology; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D012542:Scattering, Radiation; D019311:Staurosporine / Q000494:pharmacology; D013314:Stress, Mechanical; D013997:Time Factors
chemical_list: D000199:Actins; D061945:Caspase Inhibitors; D003285:Contractile Proteins; D004791:Enzyme Inhibitors; D064448:Filamins; D008840:Microfilament Proteins; D009842:Oligopeptides; C108637:aspartyl-glutamyl-valyl-aspartal; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D019311:Staurosporine