title: B2-1, a Sec7- and pleckstrin homology domain-containing protein, localizes to the Golgi complex.
abstract: 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 vesicle formation in the Golgi and endoplasmic reticulum. Recently, several groups have shown that B2-1 and highly similar proteins (e.g., ARNO, ARNO3) have varied cellular functions and subcellular locations. One of these is an association of the B2-1 Sec7 domain with the plasma membrane, binding to the cytoplasmic portion of the integrin beta2 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 plasma membrane. Here we report the subcellular localization of B2-1 protein. Interestingly, B2-1 does not localize to the plasma membrane but rather associates with a distinct Golgi complex compartment. B2-1's distribution can be disrupted by brefeldin A, a drug that rapidly disrupts the Golgi apparatus by inhibiting ARF activity. Furthermore, transient transfection of GFP-tagged B2-1 shows Golgi complex targeting. Excessive overexpression of transfected B2-1 causes partial Golgi dispersion.
authors.affiliation: Department of Biology, Dalhousie University, Halifax, Nova Scotia, B3H 4J1, Canada.
authors.forename: S Y
authors.initials: SY
authors.lastname: Lee
authors.forename: M
authors.initials: M
authors.lastname: Mansour
authors.forename: B
authors.initials: B
authors.lastname: Pohajdak
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000235:genetics*; D015153:Blotting, Western; D019556:COS Cells; D015815:Cell Adhesion Molecules / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics*; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D049452:Green Fluorescent Proteins; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics; D008856:Microscopy, Fluorescence; D010750:Phosphoproteins / Q000235:genetics*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017385:Sequence Homology; D013347:Subcellular Fractions / Q000378:metabolism; D014162:Transfection
chemical_list: D001798:Blood Proteins; D015815:Cell Adhesion Molecules; D018076:DNA, Complementary; D005656:Fungal Proteins; D020662:Guanine Nucleotide Exchange Factors; D008164:Luminescent Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; C066755:Sec7 guanine nucleotide exchange factors; C100723:cytohesin-1; C039077:platelet protein P47; D049452:Green Fluorescent Proteins