Ubiquitination of myc-tagged rhodopsin T17M. (a). Upper: ARPE-19 cells were transfected with myc-tagged rhodopsin T17M or WT expression constructs. At 24 h post-transfection, the cells were treated with MG132 (10 μM) or DMSO for 6 h. The protein was detected by immunoblotting. Lower: Immunoprecipitation of transfected myc-tagged rhodopsin T17M or WT from ARPE-19 cells after MG132 treatment. The immunoprecipitates were immunoblotted for myc and ubiquitin-V5 (b). Quantification of the relative level of ubiquitination. Data were presented as mean ± S.D. ** p < 0.01: compared to T17M cells.