Figure 6.

Degradation of human mutant proinsulin in primary rat islet cells. Islet cells were infected with adenovirus expressing mutant (Arg/Gly³²:Lys/Thr⁶⁴) or wild-type human proinsulin, pulse labeled, and chased for 1 or 6 h under basal conditions followed in each instance by 1 h of stimulation, for total chase times of 2 and 7 h, respectively. The radiolabeled proinsulin/insulin was measured in basal and stimulated chase media and in cell extracts and summed. There was loss of 23% mutant proinsulin due to degradation during the first 2 h of chase but not thereafter. There was no significant loss of wild-type human proinsulin.