Mutant GLUT4 shows less response to insulin than wild type GLUT4 in 3T3-L1 adipocytes. 3T3-L1 adipocytes were transfected with wild type (WT, black bars) or 4A mutant (MUT, grey bars) pGLUT4HA-GFP and serum-starved for 4 hr, then stimulated with 83 nM insulin for 30 min. GLUT4 translocation was measured by quantitative confocal microscopy as described in Materials and Methods. Data are means of 3 independent experiments ± SEM. A ratio of 1.0 was set for insulin-stimulated wild type cells to normalise the data between the experiments. * indicates values are significantly different (ANOVA P < 0.0005).