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J. Exp. Med.,
Volume 187, Number 4, February 16, 1998 579-586
By

From the * Department of Pathology, University of Washington School of Medicine, Seattle,
Washington 98195-7470; Normal endothelial and epithelial cells undergo apoptosis when cell adhesion and spreading are
prevented, implying a requirement for antiapoptotic signals from the extracellular matrix for
cell survival. We investigated some of the molecular changes occurring in focal adhesions during growth factor deprivation-induced apoptosis in confluent monolayers of human umbilical
vein endothelial cells. Among the first morphologic changes after initiation of the apoptotic process are membrane blebbing, loss of focal adhesion sites, and retraction from the matrix followed by detachment. We observe a specific proteolytic cleavage of focal adhesion kinase
(pp125FAK), an important component of the focal adhesion complex, and identify pp125FAK as a
novel substrate for caspase-3 and caspase-3-like apoptotic caspases. The initial cleavage precedes detachment, and coincides with loss of pp125FAK and paxillin from focal adhesion sites
and their redistribution into the characteristic membrane blebs of apoptotically dying cells.
Cleavage of pp125FAK differentially affects its association with signaling and cytoskeletal components of the focal adhesion complex; binding of paxillin, but not pp130Cas (Cas, Crk-associated
substrate) and vinculin, to the COOH terminally truncated pp125FAK is abolished. Therefore,
caspase-mediated cleavage of pp125FAK may be participating in the disassembly of the focal adhesion complex and actively interrupting survival signals from the extracellular matrix, thus propagating the cell death program.
The Cruciform Project, The Wolfson Institute for Biomedical Research,
University College London, London, United Kingdom WC1E 6JJ; and § Second Department of
Internal Medicine, Osaka City University Medical School, Osaka, Japan 545
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