FIGURE 3.

PERK regulates insulin biosynthesis at both low and high glucose concentrations. A, autoradiographs of metabolically labeled pro-insulin immunopurified from isolated rat pancreatic islets incubated for 30 min at the indicated glucose concentration in the absence or presence PERKi (1 μm) and pulse-labeled with [³⁵S]methionine/cysteine for last 10 min before harvest. Four representative experiments are shown. B, plot of the mean ± S.E. of the signal from the samples shown in A. C, autoradiographs of metabolically labeled pro-insulin immunopurified from isolated rat pancreatic islets exposed to the PERKi (P, 1 μm) or the IRE inhibitor 4μ8C (I, 30 μm) in the presence of the indicated concentration of glucose. Two representative experiments are shown. D, plot of the mean ± S.E. of the signal from the samples shown in C.