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Eur J Cell Biol. 1995 Oct;68(2):143-58.

Pericentriolar targeting of GDP-dissociation inhibitor isoform 2.

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1
Program in Molecular Medicine, University of Massachusetts Medical Center, Worcester 01605, USA.

Abstract

Cellular mechanisms for regulating membrane movements appear to involve small GTPases of the Rab subfamily. Binding of GDP-bound Rab proteins to donor membranes and their release from target membranes appear to be regulated by GDP-dissociation inhibitor (GDI) protein isoforms. Previous work showed strikingly higher levels of GDI-2 than GDI-1 fractionate with total membranes of cultured cells and are visualized in the perinuclear region in 3T3-L1 adipocytes. Here we report that GDI-2-containing structural elements are concentrated predominantly in the pericentriolar area in interphase CHO-T cells and differentiated 3T3-L1 adipocytes based on colocalization of GDI-2 and the centrosomal marker pericentrin. This finding is documented by both immunofluorescence and immunoelectron microscopy. Expressed c-Myc-tagged GDI-2 in transfected COS-7 cells targets to the same region. During mitotic resolution of the centrosome into two identifiable foci in CHO-T cells, GDI-2 containing structures remain intact and also resolve into two regions surrounding the centrosome. Dissociation of pericentriolar GDI-2 from the Golgi markers beta-COP and lectin receptors was apparent upon brefeldin A treatment of 3T3-L1 adipocytes or CHO-T cells. The integrity of pericentriolar GDI-2-binding elements was not disrupted by either brief Triton X-100 extraction or microtubule cytoskeletal disassembly, achieved with nocodazole. These data demonstrate the presence of highly ordered, detergent-resistant GDI-2-specific structural elements around the centrosome and indicate functional differences for the GDI-1 and GDI-2 protein isoforms. The results suggest the presence of selective GDI-2 acceptors in this region and a possible role of pericentriolar GDI-2 in membrane recycling.

PMID:
8575461
[Indexed for MEDLINE]
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