Figure 3. RGR-d protein expression in cultured human fetal RPE cells. Immunoblots of whole cell proteins were probed with the HRGR-DE7 antibody. The analysis included polarized human fetal RPE cells from different samples: (A) donor HFRPE-A and (B) donors HFRPE-B and HFRPE-C. A specific protein band that corresponds in size to RGR-d was found in each donor RPE cell. Cell extracts with FLAG-RGR and FLAG-RGR-d fusion proteins were used both for size comparison and as protein controls. pFLAG-hRGR, pFLAG-hRGR-d, and pFLAG-CMV-4 control expression vectors were transfected into ARPE-19 cells. Untreated ARPE-19 cells did not express detectable levels of endogenous RGR or RGR-d proteins.