FIGURE 4.

Native PAGE analyses of UGT1A isoforms in single or double expression systems. Single or multiple UGT1A isoforms were stably expressed in HEK293 cells. Total cell homogenates were solubilized with 1% Triton X-100 and 0.2% SDS, and then were subjected to a native gel. Immunoblotting was conducted with rabbit anti-human UGT1A antibody. The bands with closed and open arrowheads indicate homo- and hetero-dimers, respectively. Hetero-dimer was detected in the double expression system of UGT1A1 and UGT1A4, while such oligomer was not observed when single expression systems of UGT1A1 and UGT1A4 were mixed. Adapted from Drug Metabolism and Disposition (Fujiwara et al., 2007a).