Intracellular localization of SNAP-23 to endosomal compartments.
We have reexamined the intracellular localization of the ubiquitously expressed target membrane SNAP receptor (t-SNARE), SNAP-23. While SNAP-23 appears on the plasma membrane, in the cell types examined there is a significant pool associated with endosomal compartments. Immuno-staining and expression of green fluorescent protein-tagged SNAP-23, show that it has a punctate, perinuclear localization in HepG2 and HT4 cells. This distribution overlaps significantly with transferrin receptor and slightly with the late endosome/lysosomal protein LAMP-1. The localization of SNAP-23 changes as HepG2 cells polarize. Initially it is concentrated at sites of cell-cell contact and then almost exclusively to the apical (or bile canalicular) domain of the cell. These data are consistent with a role for SNAP-23 in both endosome-plasma membrane trafficking as well as endosome-endosome transport.
Department of Biochemistry, University of Kentucky College of Medicine, Chandler Medical Center, Lexington 40536, USA.
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D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000737:chemistry / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis / Q000276:immunology / Q000378:metabolism*; D002451:Cell Compartmentation; D002460:Cell Line; D016764:Cell Polarity; D011992:Endosomes / Q000737:chemistry / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007106:Immune Sera / Q000032:analysis; D007424:Intracellular Fluid / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D051381:Rats; D013194:Staining and Labeling; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D007106:Immune Sera; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; C100493:SNAP23 protein, human; C107017:Snap23 protein, mouse