3H-fucose incorporation into RPE cell surface proteins of normal and dystrophic rats

Glycoproteins were metabolically labeled with 3H-fucose in cultured RPE cells from RCS rdy-p+ and Long Evans rats. 3H-labeled glycoproteins associated with a plasma membrane-enriched subcellular fraction were separated by two-dimensional gel electrophoresis. Relative incorporation of 3H-fucose into high molecular weight cell surface glycoproteins (Mr of 128,000-183,000) was measured by quantitative autoradiography and densitometry. The results of these experiments show that 3H-fucose incorporation into four glycoproteins (Mr of 183,000, 175,000, 164,000 and 156,000) was reduced by 30-50% in the dystrophic RPE as compared to the normal cells. This reduction was not due to an absence of the protein core of glycoproteins on the dystrophic RPE cell surface; when RPE cells were labeled with 3H-leucine prior to analysis, no reduction in label was found in the dystrophic RPE as compared to normal. Therefore, the results of this study suggest that the RCS rat RPE processes the oligosaccharide portion of some cell surface glycoproteins differently than normal rat RPE.