Loss of insulin granules in INS-1 cells. (A) Endogenous BAIAP3 in INS-1 cells and pancreas. (B) Loss of PC2 and insulin after BAIAP3 knockdown (BAIAP3KD) in INS-1 cells. n = 3. KD, knockdown; NT, nontargeting. (C and D) Quantification of PC2 (C) and insulin (D) normalized to tubulin. n = 3. (E) Loss of insulin granules after BAIAP3 knockdown and rescue with lysosome inhibitors (LI; pepstatin A, 10 µg/ml; E64D, 10 µg/ml). Bars, 10 µm. (F) Rescue of PC2 with lysosome inhibitors. + = 1 µg/ml; ++ = 10 µg/ml. (A, B, and F) Molecular mass is shown in kilodaltons. (G) Glucose-induced insulin secretion. Basal release (1.5 mM glucose) from nontargeting cells is set as 1. n = 6. (H) Electron microscope analysis of INS-1 cells in the presence of lysosome inhibitors. Bars:1 µm; (inset) 0.5 µm. (I) Counting of multigranular bodies in INS-1 cells. n = 35, 72, 39, and 32 cells from left to right. See also Fig. S3. (C, D, and G) Data are expressed as mean ± SD. P-values were obtained by a two-tailed Student’s t test. (I) Data are expressed as median ± quantile. P-values were obtained by Wilcoxon test. *, P < 0.05; **, P < 0.01.