The Role of Actin-binding Protein 280 in Integrin-dependent Mechanoprotection*
- Michael Glogauer‡§,
- Pam Arora‡,
- Deborah Chou‡,
- Paul A. Janmey¶,
- Gregory P. Downey‖ and
- Christopher A. G. McCulloch‡
- From the ‡MRC Group in Periodontal Physiology, Faculty of Dentistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada, the ¶Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, and the ‖Faculty of Medicine, Department of Medicine, University of Toronto, Toronto, Ontario M5S 1A8, Canada
Abstract
To survive in a mechanically active environment, cells must adapt to variations of applied membrane tension. A collagen-coated magnetic bead model was used to apply forces directly to the actin cytoskeleton through integrin receptors. We demonstrate here that by a calcium-dependent mechanism, human fibroblasts reinforce locally their connection with extracellular adhesion sites by inducing actin assembly and by recruiting actin-binding protein 280 (ABP-280) into cortical adhesion complexes. ABP-280 was phosphorylated on serine residues as a result of force application. This phosphorylation and the force-induced actin reorganization were largely abrogated by inhibitors of protein kinase C. In a human melanoma cell line that does not express ABP-280, actin accumulation could not be induced by force, whereas in stable transfectants expressing ABP-280, force-induced actin accumulation was similar to human fibroblasts. Cortical actin assembly played a role in regulating the activity of stretch-activated, calcium-permeable channels (SAC) since sustained force application desensitized SAC to subsequent force applications, and the decrease in stretch sensitivity was reversed after treatment with cytochalasin D. ABP-280-deficient cells showed a >90% increase in cell death compared with ABP-280+ve cells after force application. We conclude that ABP-280 plays an important role in mechanoprotection by reinforcing the membrane cortex and desensitizing SACs.
Footnotes
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↵* This work was supported by a Group grant from the Medical Research Council of Canada (to C. A. G. M.) and an MRC Dental Fellowship (to M. G.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵§ To whom correspondence should be addressed: Rm. 4384, Medical Sciences Bldg., University of Toronto, Toronto, Ontario, Canada M5S 1A8. Tel.: 416-978-6687; Fax: 416-978-5956.
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↵1 The abbreviations used are: ABP, actin-binding protein; SAC, stretch-activated, calcium-permeable channels; TRITC, tetramethylrhodamine isothiocyanate; Pipes, 1,4-piperazinediethanesulfonic acid; BSA, bovine serum albumin; PBS, phosphate-buffered saline; BAPTA/AM, 1,2-(bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid; BIM, bisindolylmaleimide; MARCKS, myristoylated alanine-rich C kinase substrate; PKC, protein kinase C.
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- Received September 3, 1997.
- Revision received November 3, 1997.
- The American Society for Biochemistry and Molecular Biology, Inc.
