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  • Cathepsin B contributes to autophagy-related 7 (Atg7)-induced nod-like receptor 3 (NLRP3)-dependent proinflammatory response and aggravates lipotoxicity in rat insulinoma cell line.

Cathepsin B contributes to autophagy-related 7 (Atg7)-induced nod-like receptor 3 (NLRP3)-dependent proinflammatory response and aggravates lipotoxicity in rat insulinoma cell line.

The Journal of biological chemistry (2013-08-30)
Shali Li, Leilei Du, Lu Zhang, Yue Hu, Wenchun Xia, Jia Wu, Jing Zhu, Lingling Chen, Fengqi Zhu, Chunxian Li, Sijun Yang
ABSTRACT

Impairment of glucose-stimulated insulin secretion caused by the lipotoxicity of palmitate was found in β-cells. Recent studies have indicated that defects in autophagy contribute to pathogenesis in type 2 diabetes. Here, we report that autophagy-related 7 (Atg7) induced excessive autophagic activation in INS-1(823/13) cells exposed to saturated fatty acids. Atg7-induced cathepsin B (CTSB) overexpression resulted in an unexpected significant increase in proinflammatory chemokine and cytokine production levels of IL-1β, monocyte chemotactic protein-1, IL-6, and TNF-α. Inhibition of receptor-interacting protein did not affect the inflammatory response, ruling out involvement of necrosis. CTSB siRNA suppressed the inflammatory response but did not affect apoptosis significantly, suggesting that CTSB was a molecular linker between autophagy and the proinflammatory response. Blocking caspase-3 suppressed apoptosis but did not affect the inflammatory response, suggesting that CTSB induced inflammatory effects independently of apoptosis. Silencing of Nod-like receptor 3 (NLRP3) completely abolished both IL-1β secretion and the down-regulation effects of Atg7-induced CTSB overexpression on glucose-stimulated insulin secretion impairment, thus identifying the NLRP3 inflammasome as an autophagy-responsive element in the pancreatic INS-1(823/13) cell line. Combined together, our results indicate that CTSB contributed to the Atg7-induced NLRP3-dependent proinflammatory response, resulting in aggravation of lipotoxicity, independently of apoptosis in the pancreatic INS-1(823/13) cell line.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Cathepsin B from human placenta, lyophilized powder, ≥5 units/mg protein
Sigma-Aldrich
Cathepsin B from human liver, buffered aqueous solution, ≥1,500 units/mg protein (E1%/280)
Sigma-Aldrich
Anti-LC3 antibody produced in rabbit, ~1 mg/mL, affinity isolated antibody, buffered aqueous solution
Sigma-Aldrich
Cathepsin B from bovine spleen, lyophilized powder, ≥10 units/mg protein