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First published online July 23, 2007
doi: 10.1242/10.1242/jcs.003566

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PKC and cofilin activation affects peripheral actin reorganization and cell-cell contact in cells expressing integrin 5 but not its tailless mutant

¹ Cancer Research Institute, College of Medicine, Seoul National University, 28, Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea
² Department of Tumor Biology, Seoul National University, 28, Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea
³ Department of Molecular and Clinical Oncology, Seoul National University, 28, Yeongeon-dong, Jongno-gu, Seoul 110-799, Korea
⁴ Laboratory of Angiogenesis and Chemoprevention, CPMDRC, College of Oriental Medicine, Kyunghee University, 1 Hoegidong, Dongdaemugu, Seoul 131-701, Korea

^* Author for correspondence (e-mail: sungkim7{at}khu.ac.kr; jwl{at}snu.ac.kr)

Accepted 2 June 2007

Integrin-mediated cell adhesion transduces signaling activities for actin reorganization, which is crucially involved in cellular function and architectural integrity. In this study, we explored the possibility of whether cell-cell contacts might be regulated via integrin-51-mediated actin reorganization. Ectopic expression of integrin 5 in integrin-5-null intestinal epithelial cells resulted in facilitated retraction, cell-cell contact loss, and wound healing depending on Src and PI3K (phosphoinositide 3-kinase) activities by a reagent that affects actin organization. However, cytoplasmic tailless integrin 5 (hereafter referred to as 5/1) expression caused no such effects but rather sustained peripheral actin fibers, regardless of Src and PI3K signaling activities. Furthermore, integrin 5 engagement with fibronectin phosphorylated Ser643 of PKC, upstream of FAK and Src and at a transmodulatory loop with PI3K/Akt. Pharmacological PKC inactivation, dominant-negative PKC adenovirus or inactive cofilin phosphatase (SSH1L mutant) retrovirus infection of 5-expressing cells sustained peripheral actin organization and blocked the actin reorganizing-mediated loss of cell-cell contacts. Meanwhile, wild-type PKC expression sensitized 5/1-expressing cells to the actin disruptor to induce cell scattering. Altogether, these observations indicate that integrin 5, but not 5/1, mediates PKC phosphorylation and cofilin dephosphorylation, which in turn modulate peripheral actin organization presumably leading to an efficient regulation of cell-cell contact and migration.

Key words: PKC, Cofilin, Actin organization, Cell contacts, Integrin

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