A Glut4-vesicle marker protein, insulin-responsive aminopeptidase, is localized in a novel vesicular compartment in PC12 cells.
Glut4-containing vesicles represent a regulated recycling compartment in insulin-sensitive fat and skeletal muscle cells, the nature and origin of which are not fully understood. In addition to Glut4 itself, these vesicles compartmentalize a number of proteins, at least one of which, insulin-responsive aminopeptidase, or IRAP, is completely colocalized with Glut4 in insulin-sensitive tissues. However, unlike Glut4, IRAP is expressed in a variety of other tissues and cell lines. Here, we explored the intracellular localization of IRAP in the rat pheochromocytoma cell line PC12. We found that this protein is present in a distinct population of slowly recycling light vesicles. By gradient centrifugations, immunoadsorption and double immunofluorescent staining, these vesicles are different from transferrin-containing endosomes, small synaptic vesicles and secretory granules and may thus represent a novel compartment in PC12 cells. Glut4-GFP chimera transiently expressed in PC12 cells is targeted to IRAP-containing vesicles indicating that cotargeting of Glut4 and IRAP is not specific for adipocytes and myocytes, but is faithful in a foreign cell type. We suggest that PC12 cells may possess a novel type of a vesicular carrier that may represent the homolog of Glut4-vesicles.
Thoidis
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Boston University School of Medicine, Boston, MA 02118, USA.
Kandror
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KV
D000327:Adsorption; D000818:Animals; D019921:Biotinylation; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D051275:Glucose Transporter Type 4; D007328:Insulin / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis*; D009124:Muscle Proteins; D016716:PC12 Cells; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism; D013997:Time Factors; D014162:Transfection
D051275:Glucose Transporter Type 4; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; C495694:Slc2a4 protein, rat