Functional comparison of the role of dynamin 2 splice variants on GLUT-4 endocytosis in 3T3L1 adipocytes.
Previously, we reported that expression of a dominant-interfering neuronal-specific dynamin 1 (K44A/dynamin 1) inhibited the plasma membrane internalization of GLUT-4 in 3T3L1 adipocytes (15). To investigate the role of the ubiquitously expressed isoform of dynamin, dynamin 2, on adipocyte GLUT-4 internalization, and to determine whether dynamin splice variants have functional specificity, we expressed each of the four dynamin 2 isoforms (aa, ab, ba, and bb) as either wild-type proteins or GTPase-defective mutants. When expressed as enhanced green fluorescent protein (EGFP) fusions, these isoforms were found to have overlapping subcellular distributions being localized throughout the cell cytoplasm, on punctate vesicles and in a perinuclear compartment. This distribution was qualitatively similar to that of endogenous dynamin 2 and overlapped with GLUT-4 in the basal state. Expression of wild-type dynamin 2 isoforms had no effect on the basal or insulin-stimulated distribution of GLUT-4; however, expression of the dominant-interfering dynamin 2 mutants inhibited GLUT-4 endocytosis. These data demonstrate that dynamin 2 is required for GLUT-4 endocytosis in 3T3L1 adipocytes and suggest that, relative to GLUT-4 trafficking, the dynamin 2 splice variants have overlapping functions and are probably not responsible for mediating distinct GLUT-4 budding events.
Kao
A W
AW
Department of Physiology and Biophysics, The University of Iowa, Iowa City, IA 52242-1109, USA.
Yang
C
C
Pessin
J E
JE
D016475:3T3 Cells; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D034284:Dynamin I; D034281:Dynamins; D004705:Endocytosis; D005455:Fluorescent Antibody Technique; D020558:GTP Phosphohydrolases / Q000235:genetics* / Q000502:physiology*; D015870:Gene Expression; D051275:Glucose Transporter Type 4; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics; D051379:Mice; D008856:Microscopy, Fluorescence; D009004:Monosaccharide Transport Proteins / Q000378:metabolism*; D009124:Muscle Proteins; D009154:Mutation; D012326:RNA Splicing; D051381:Rats; D011993:Recombinant Fusion Proteins; D014162:Transfection
D051275:Glucose Transporter Type 4; D008164:Luminescent Proteins; D009004:Monosaccharide Transport Proteins; D009124:Muscle Proteins; D011993:Recombinant Fusion Proteins; C495693:Slc2a4 protein, mouse; C495694:Slc2a4 protein, rat; D049452:Green Fluorescent Proteins; D034284:Dynamin I; D020558:GTP Phosphohydrolases; D034281:Dynamins