Caspase-dependent cleavage of tensin induces disruption of actin cytoskeleton during apoptosis q Seunghyi Kook, a,b Do Hoon Kim, a Sang Ryeol Shim, a Wook Kim, a Jang-Soo Chun, a and Woo Keun Song a, * a Department of Life Science, Kwangju Institute of Science and Technology, 1 Oryong-dong, Puk-gu, Kwangju 500-712, South Korea b Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0295, USA Received 14 February 2003 Abstract Members of both calpain and caspase protease families can degrade several components of focal adhesions, leading to disas- sembly of these complexes. In this report, we investigated the disappearance of tensin from cell adhesion sites of chicken embryonic fibroblast cells (CEFs) exposed to etoposide and demonstrated that loss of tensin from cell adhesions during etoposide-induced apoptosis may be due to degradation of tensin by caspase-3. Tensin cleavage by caspase-3 at the sequence DYPD 1226 G separates the amino-terminal region containing the actin binding domain and the carboxyl-terminal region containing the SH2 domain. The resultant carboxyl-terminal fragment of tensin is unable to bind phosphoinositide 3-kinase (PI3-kinase) transducing cell survival signaling. We also demonstrated that overexpression of the amino-terminal tensin fragment induced disruption of actin cytoskeleton in chicken embryonic fibroblasts. Therefore, caspase-mediated cleavage of tensin contributes to the disruption of actin organization and interrupts ECM-mediated survival signals through phosphatidylinositol 3-kinase. Ó 2003 Elsevier Science (USA). All rights reserved. Keywords: Focal adhesion complex degradation; Tensin degradation during apoptosis; Disruption of actin cytoskeleton Apoptosis is a fundamental and complex biological process that enables an organism to eliminate unwanted or defective cells through an orderly process of cellular disintegration [1–3]. Apoptosis is characterized by morphological changes including nuclear condensation, cell shrinkage, membrane blebbing, and detachment from extracellular matrix (ECM). The induction of ap- optosis involves the proteolytic activation of a cascade of cysteine proteases called caspases. Caspases contrib- ute to cell death by directly inactivating negative regu- lators of apoptosis and by promoting the disassembly of cellular structures such as focal adhesion complexes [4]. Interaction of cells with ECM is mediated by integrin receptors on the cell surface [5]. Integration of the in- tracellular signaling and structural responses initiated by ECM-integrin engagement may be mediated through the focal adhesion complex [6]. The focal adhesion complex consists of numerous, tightly associated, structural and signaling proteins, and the cytoplasmic tail of b integrin, thereby providing intracellular signal transduction ma- chinery and also serving as a physical link between the ECM and the cytoskeleton [7]. The structure and func- tions of focal adhesion complex may influence the signal transduction pathways associated with cytoskeletal re- arrangement and play key roles in many biological process. In addition, the transition from flat to round cell morphology, which is a characteristic feature in cells undergoing apoptosis, is accompanied by cytoskeletal rearrangement and changes in focal adhesion proteins. In epithelial and endothelial cells, disruption of integrin contacts results in the induction of apoptosis [8,9] and the recent studies demonstrated that several focal Biochemical and Biophysical Research Communications 303 (2003) 37–45 www.elsevier.com/locate/ybbrc BBRC q Abbreviations: CEFs, chicken embryonic fibroblasts; FAK, focal adhesion kinase; ECM, extracellular matrix; ZVAD-fmk, ZVAD- fluoromethylketone; DEVD-cmk, DEVD-chloromethylketone; PENN/ MMAC1, phosphatase and tensin homologue on chromosome 10/ mutated in multiple advanced cancers. * Corresponding author. Fax: +82-62-970-2484. E-mail address: wksong@kjist.ac.kr (W.K. Song). 0006-291X/03/$ - see front matter Ó 2003 Elsevier Science (USA). All rights reserved. doi:10.1016/S0006-291X(03)00280-8