Work

Clathrin-mediated Endocytosis of Alpha-1 Antitrypsin is Essential for its Protective Function in Islet Cell Survival

Year: 2019

Type: article

Abstract: Cytokine-induced pancreatic β cell death plays a pivotal role in both type 1 and type 2 diabetes.Our previous study showed that alpha-1 antitrypsin (AAT) inhibits β cell death through the suppression of cytokine-induced c-Jun N-terminal kinase (JNK) activation in an islet transplantation model.The aim of this study was to further understand how AAT impacts β cells by studying AAT endocytosis in human islets and a βTC3 murine insulinoma cell line.Methods: In vitro, human islets and βTC3 cells were stimulated with cytokines in the presence or absence of chlorpromazine (CPZ), a drug that disrupts clathrin-mediated endocytosis.Western blot, real-time PCR and cell death ELISA were performed to investigate β cell death.The oxygen consumption rate (OCR) was measured on human islets.In vivo, islets were harvested from C57BL/6 donor mice treated with saline or human AAT and transplanted into the livers of syngeneic mice that had been rendered diabetic by streptozotocin (STZ).Islet graft survival and function were analyzed.Results: AAT was internalized by β cells in a time-and dose-dependent manner.AAT internalization was mediated by clathrin as treatment with CPZ, profoundly decreased AAT internalization, cytokine-induced JNK activation and the downstream upregulation of c-Jun mRNA expression.Similarly, addition of CPZ attenuated cytokine-induced caspase 9 cleavage (c-casp 9) and DNA fragmentation, which was suppressed by AAT.Treatment of donor mice with AAT produced AAT internalization in islets, and resulted in a higher percentage of recipients reaching normoglycemia after syngeneic intraportal islet transplantation.Conclusion: Our results suggest that AAT is internalized by β cells through clathrin-mediated endocytosis that leads to the suppression of caspase 9 activation.This process is required for the protective function of AAT in islets when challenged with proinflammatory cytokines or after islet transplantation.

Source: Theranostics

DOI: 10.7150/thno.31647

Authors: Jingjing Wang, Wenyu Gou, Do-sung Kim, Charlie Strange, Hongjun Wang

Institution: Medical University of South Carolina

Language: English

Topic: Pancreatic function and diabetes

Subfield: Surgery

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: gold

Estimated APC paid: $1,671