POSH Antibody (M-290): sc-28866

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Rho, Rac and Cdc42 are members of the small GTPase family. These proteins act as molecular switches, cycling between an active GTP-bound state and an inactive GDP-bound state (1). Activation of these proteins results in rearrangements of filamentous actin and the formation of actin stress fibers (2,3). Many of the targets of these GTPases are involved in signal transduction events mediated by Src3 homology (SH3) domains (4,5). POSH, for “plenty of SH3s”, is a Rac binding protein with four SH3 domains. POSH preferentially interacts with the GTP form of RAC and not with the GDP-bound RAC. Ectopic expression of POSH elicits JNK activation and nuclear translocation of NFkB, suggesting that POSH is involved in Rac regulation of these kinase pathways. Overexpression of POSH has also been shown to induce apoptosis (6).