title: Cathepsin inhibition-induced lysosomal dysfunction enhances pancreatic beta-cell apoptosis in high glucose.
abstract: Autophagy is a lysosomal degradative pathway that plays an important role in maintaining cellular homeostasis. We previously showed that the inhibition of autophagy causes pancreatic β-cell apoptosis, suggesting that autophagy is a protective mechanism for the survival of pancreatic β-cells. The current study demonstrates that treatment with inhibitors and knockdown of the lysosomal cysteine proteases such as cathepsins B and L impair autophagy, enhancing the caspase-dependent apoptosis of INS-1 cells and islets upon exposure to high concentration of glucose. Interestingly, treatment with cathepsin B and L inhibitors prevented the proteolytic processing of cathepsins B, D and L, as evidenced by gradual accumulation of the respective pro-forms. Of note, inhibition of aspartic cathepsins had no effect on autophagy and cell viability, suggesting the selective role of cathepsins B and L in the regulation of β-cell autophagy and apoptosis. Lysosomal localization of accumulated pro-cathepsins in the presence of cathepsin B and L inhibitors was verified via immunocytochemistry and lysosomal fractionation. Lysotracker staining indicated that cathepsin B and L inhibitors led to the formation of severely enlarged lysosomes in a time-dependent manner. The abnormal accumulation of pro-cathepsins following treatment with inhibitors of cathepsins B and L suppressed normal lysosomal degradation and the processing of lysosomal enzymes, leading to lysosomal dysfunction. Collectively, our findings suggest that cathepsin defects following the inhibition of cathepsin B and L result in lysosomal dysfunction and consequent cell death in pancreatic β-cells.
authors.affiliation: Department of Brain Science, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea.
authors.forename: Minjeong
authors.initials: M
authors.lastname: Jung
authors.affiliation: Department of Brain Science, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea.
authors.forename: Jaemeun
authors.initials: J
authors.lastname: Lee
authors.affiliation: Department of Brain Science, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea.
authors.forename: Hye-Young
authors.initials: HY
authors.lastname: Seo
authors.affiliation: Department of Brain Science, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea.
authors.forename: Ji Sun
authors.initials: JS
authors.lastname: Lim
authors.affiliation: Department of Brain Science, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea; Neurometabolomics Research Center, Daegu Gyeongbuk Institute of Science & Technology, Daegu, Korea.
authors.forename: Eun-Kyoung
authors.initials: EK
authors.lastname: Kim
mesh_terms: D000818:Animals; D017209:Apoptosis; D002401:Cathepsin B / Q000037:antagonists & inhibitors / Q000378:metabolism*; D056668:Cathepsin L / Q000037:antagonists & inhibitors / Q000378:metabolism*; D045744:Cell Line, Tumor; D003920:Diabetes Mellitus / Q000201:enzymology / Q000473:pathology; D005947:Glucose / Q000502:physiology; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000502:physiology*; D008247:Lysosomes / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D002401:Cathepsin B; D056668:Cathepsin L; D005947:Glucose; D008869:Microtubule-Associated Proteins; D011480:Protease Inhibitors; C526109:Anxa3 protein, rat