The PIX–GIT complex: A G protein signaling cassette in control of cell shape

Arf and Rho GTP-binding proteins coordinately regulate membrane dynamics and cytoskeletal rearrangements. The Cdc42/Rac guanine nucleotide exchange factor PIX and the Arf GTPase-activating protein GIT form a stable complex in cells. The PIX–GIT complex functions to integrate signaling among Arf, Cdc42, and Rac proteins in response to cues emanating from integrins, heterotrimeric G proteins, receptor tyrosine kinases, and cell–cell interactions. A concept that emerges from the literature is that the PIX–GIT complex serves as a cassette to elicit changes in cell shape essential for polarized cell responses in a wide range of biological contexts.