B2-1, a Sec7-and pleckstrin homology domain-containing protein, localizes to the Golgi complex

B2-1 is a human protein that contains both a Sec7 and a pleckstrin homology domain. The yeast Sec7 protein was previously shown to be involved in vesi cle formation in the Golgi and endoplasmic reticulum, Recently, several gro ups have shown that B2-1 and highly similar proteins (e.g., ARNO, ARNO3) ha ve varied cellular functions and subcellular locations, One of these is an association of the B2-1 Sec7 domain with the plasma membrane, binding to th e cytoplasmic portion of the integrin beta 2 chain (CD18) and is postulated to be involved in inside-out signaling, Other groups have shown that B2-1 and these related proteins are guanine nucleotide-exchange factors that act upon ADP ribosylation factors (ARFs) and are localized to the Golgi or pla sma membrane. Here we report the subcellular localization of B2-1 protein. Interestingly, B2-1 does not localize to the plasma membrane but rather ass ociates with a distinct Golgi complex compartment, B2-1's distribution can be disrupted by brefeldin A, a drug that rapidly disrupts the Golgi apparat us by inhibiting ARF activity. Furthermore, transient transfection of GFP-t agged B2-1 shows Golgi complex targeting. Excessive overexpression of trans fected B2-1 causes partial Golgi dispersion. (C) 2000 Academic Press.