We then examined if the A118G SNP affected maturation and stability of the MOPR with pulse-chase experiments on hMOPRs stably expressed in CHO cells (Fig. 6). Cells were incubated with [35S]Met/Cys-containing medium at 37°C for 60 min (pulse). Following removal of the medium, cells were incubated with complete medium (chase) for specified time periods indicated in Fig. 6. At 0 h, the Mr ranges of the precursors of A118/N40-hMOPR and G118/D40-hMOPR were 52-56 kDa and 50-54 kDa, respectively. The precursors were gradually transformed into the mature/fully glycosylated forms of the 81 kDa-band and 76 kDa-band, respectively over time (0-2h). The two MOPR variants have similar extents of conversion from the precursor form to the mature form (from 0 h to 2 h, 87±25 vs 82±16 %, n=3). The peak levels of the mature forms were reached at 2 h for both hMOPR variants (Fig. 6A). With their peak levels as 100%, the levels of the mature forms of A118/N40-hMOPR and G118/D40-hMOPR were quantified at various time points (Fig. 6B) and their half-lives were determined. As evident in Fig. 6B, the
