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Article
Subject Categories: Signal Transduction
The EMBO Journal (2006) 25, 2062–2074, doi:10.1038/sj.emboj.7601098
Published online 20 April 2006
Phospholipase Cgamma/diacylglycerol-dependent activation of beta2-chimaerin restricts EGF-induced Rac signaling
HongBin Wang1, Chengfeng Yang1, Federico Coluccio Leskow1, Jing Sun1, Bertram Canagarajah2, James H Hurley2 and Marcelo G Kazanietz1
1 Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
2 Laboratory of Molecular Biology, NIDDK, NIH, Bethesda, MD, USA

To whom correspondence should be addressed
Marcelo G Kazanietz, Department of Pharmacology, University of Pennsylvania School of Medicine, 816 BRB II/III, 421 Curie Blvd., Philadelphia, PA 19104-6160, USA. Tel.: +1 215 898 0253; Fax: +1 215 573 9004; E-mail: marcelo@spirit.gcrc.upenn.edu

Received 17 October 2005; Accepted 27 March 2006; Published online 20 April 2006.
Abstract
Although receptor-mediated regulation of small G-proteins and the cytoskeleton is intensively studied, the mechanisms for attenuation of these signals are poorly understood. In this study, we have identified the Rac-GAP beta2-chimaerin as an effector of the epidermal growth factor receptor (EGFR) via coupling to phospholipase Cgamma (PLCgamma) and generation of the lipid second messenger diacylglycerol (DAG). EGF redistributes beta2-chimaerin to promote its association with the small GTPase Rac1 at the plasma membrane, as determined by FRET. This relocalization and association with Rac1 were impaired by disruption of the beta2-chimaerin C1 domain as well as by PLCgamma1 RNAi, thus defining beta2-chimaerin as a novel DAG effector. On the other hand, GAP-deficient beta2-chimaerin mutants show enhanced translocation and sustained Rac1 association in the FRET assays. Remarkably, RNAi depletion of beta2-chimaerin significantly extended the duration of Rac activation by EGF, suggesting that beta2-chimaerin serves as a mechanism that self-limits Rac activity in response to EGFR activation. Our results represent the first direct evidence of divergence in DAG signaling downstream of a tyrosine-kinase receptor via a PKC-independent mechanism.
Keywords: beta2-chimaerin, diacylglycerol, EGF, Phorbol esters, Rac
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