Mechanisms for reversible regulation between G13 and Rho exchange factors

被引:85
作者
Wells, CD
Liu, MY
Jackson, M
Gutowski, S
Sternweis, PM
Rothstein, JD
Kozasa, T
Sternweis, PC
机构
[1] Univ Texas, SW Med Ctr, Dept Pharmacol, Dallas, TX 75390 USA
[2] Hybrigen Inc, Dallas, TX 75207 USA
[3] Johns Hopkins Univ, Dept Neurol & Neurosci, Baltimore, MD 21287 USA
[4] Univ Illinois, Dept Pharmacol, Chicago, IL 60612 USA
[5] Univ Illinois, Dept Anat & Cell Biol, Chicago, IL 60612 USA
关键词
D O I
10.1074/jbc.M105274200
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The heterotrimeric G proteins, G(12) and G(13), mediate signaling between G protein-coupled receptors and the monomeric GTPase, RhoA. One pathway for this modulation is direct stimulation by Galpha(13) of p115 RhoGEF, an exchange factor for RhoA. The GTPase activity of both Galpha(12) and Galpha(13) is increased by the N terminus of p115 Rho guanine nucleotide exchange factor (GEF). This region has weak homology to the RGS box sequence of the classic regulators of G protein signaling (RGS), which act as GTPase-activating proteins (GAP) for G(i) and G(q). Here, the RGS region of p115 RhoGEF is shown to be distinctly different in that sequences flanking the predicted "RGS box" region are required for both stable expression and GAP activity. Deletions in the N terminus of the protein eliminate GAP activity but retain substantial binding to Galpha(13) and activation of RhoA exchange activity by Galpha(13). In contrast, GTRAP48, a homolog of p115 RhoGEF, bound to Galpha(13) but was not stimulated by the a subunit and had very poor GAP activity. Besides binding to the N-terminal RGS region, Galpha(13) also bound to a truncated protein consisting only of the Dbl homology (DH) and pleckstrin homology (PH) domains. However, Galpha(13) did not stimulate the exchange activity of this truncated protein. A chimeric protein, which contained the RGS region of GTRAP48 in place of the endogenous N terminus of p115 RhoGEF, was activated by Galpha(13). These results suggest a mechanism for activation of the nucleotide exchange activity of p115 RhoGEF that involves direct and coordinate interaction of Galpha(13) to both its RGS and DH domains.
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收藏
页码:1174 / 1181
页数:8
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