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Requirement of protein phosphatase 2A for recruitment of IQGAP1 to Rac-bound β1 integrin

✍ Scribed by Katsuo Suzuki; Yasuhiro Chikamatsu; Kazuhide Takahashi

Publisher
John Wiley and Sons
Year
2005
Tongue
English
Weight
249 KB
Volume
203
Category
Article
ISSN
0021-9541

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✦ Synopsis

Abstract

Serine/threonine protein phosphatase (PP) 2A is thought to dephosphorylate phosphorylated β1 integrin to link with actin filaments (F‐actin). However, whether PP2A participates in the regulation of F‐actin assembly to which β1 integrin is anchored is unclear. We report here that the core enzyme of PP2A (PP2A‐AC), consisting of the regulatory subunit A (PP2A‐A) and the catalytic subunit C (PP2A‐C), forms a complex with β1 integrin, a small GTPase Rac, and its effector IQGAP1 in non‐malignant human mammary epithelial (HME) cells. Treatment of HME cells with okadaic acid (OA), an inhibitor of PP2A, caused cell rounding, reduction in F‐actin assembly that links with β1 integrin, and dissociation of IQGAP1‐bound PP2A‐AC from Rac‐β1 integrin. The dissociation of IQGAP1‐PP2A‐AC was accompanied by loss of F‐actin gelating activity of Rac‐β1 integrin. In breast cancer MCF‐7 cells, which possess PP2A‐C but lack PP2A‐A, IQGAP1 was not associated with Rac‐β1 integrin but with PP2A‐C, with no distinct F‐actin assembly that linked to Rac‐β1 integrin even before treatment with OA. We therefore propose that PP2A, especially PP2A‐A, functions to maintain F‐actin assembly to which β1 integrin is anchored by recruitment of IQGAP1 to Rac‐β1 integrin. © 2004 Wiley‐Liss, Inc.

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