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. 2012 Jan 10;302(6):E714–E723. doi: 10.1152/ajpendo.00486.2011

Fig. 4.

Fig. 4.

Intracellular retention of GLP-1R when coexpressed with SUMO-1. A: GLP-1R-GFP expressed with mCherry vector shows a predominant plasma membrane fluorescence of the GLP-1R-GFP. B: GLP-1R-GFP expressed with mCherry-SUMO-1 shows decreased plasma membrane localization consistent with enhanced intracellular retention. C: enlarged image of a representative cell expressing GLP-1R-GFP and mCherry. Vertical line represents the line chosen for fluorescence line scan. D: enlarged image of a cell expressing GLP-1R-GFP and mCherry SUMO-1 with the line chosen for the line scan. E: top, representative fluorescence line scan of GLP-1R-GFP with mCherry in cell C that shows distinct peaks. Bottom, fluorescence line scan of GLP-1R-GFP with mCherry-SUMO-1 that shows uniform distribution. F: mean fluorescence ratio of membrane to cytosol shows 2.2-fold increase, indicating enhanced membrane fluorescence when SUMO-1 is not present. Error bars indicate means ± SD; n = 6. Student's t-test: ***P < 0.0007; n = 12–15 cells from multiple dishes. Average length of the line scan at the membrane and cytosol for calculating the ratio is 0.4–0.5 μm. G: GLP-1R-HA coexpressed with GFP shows predominant plasma membrane fluorescence of the GLP-1R signal, detected with anti-HA antibody in nonpermeabilized cells. H: MIN6 cells transfected with the HA-GLP-1R construct coexpressed with mCherry-SUMO-1 and stained with anti-HA antibody shows diminished plasma membrane fluorescence of GLP-1R-HA in nonpermeabilized cells. Scale bar = 5 μm.