Figure 8. Secretory rescue by WT proinsulin is restricted to a subset of MIDY mutants.

293T cells transiently cotransfected with plasmids expressing the indicated hPro mutants and either empty vector or WT mPro were incubated overnight in growth medium beginning at 24 hours after transfection. Media were collected, and hPro secretion was measured by RIA. The data shown (fold increase in mutant proinsulin secretion as a consequence of expressing WT mPro over empty vector) are mean values ± range from 2 independent experiments. X, undetectable.