CYTOHESIN1

(= B2-1)

Guanine nucleotide exchange factor for human ADP-ribosylation factor (ARF) GTPases. Abundant in cells of the immune system where it mediates PI3-kinase activation of b 2 integrin (particularly LFA-1) through interaction with the cytoplasmic domain. Closely related to ARNO and GRP-1; all three have a central Sec7-like domain and C-terminal pleckstrin homology (PH) domain. The PH domain and C-terminal polybasic sequence are important for membrane-association and function.