Up to date, most of the diabetes-associated genes identified in genome-wide association studies are enriched in the pancreatic beta cells. Beta cell failure plays a central role in the development and progression of type 2 diabetes (T2D). The endoplasmic reticulum (ER) is a central organelle for the massive production and processing of proinsulin. ER homeostasis is critical for normal beta cell function and is maintained by the delicate balance between protein synthesis, folding, export and degradation. In contrast, the disruption of ER homeostasis, by many genetic and environmental diabetes-causing factors, induces ER stress and causes beta cell death in T2D. Compared to our knowledge in protein synthesis, folding and degradation in beta cell ER, the role of ER export in proinsulin biogenesis and ER homeostasis is much less understood. This proposal addresses this knowledge gap. We have obtained strong preliminary results demonstrating that ER exit of proinsulin requires COPII (coat protein complex II) coated vesicles and defective COPII dependent ER export strongly induces ER stress. In addition to our results, evidence has recently begun to emerge that reduced ER-Golgi transport is causative to lipotoxicity-induced ER stress in beta cells. On the basis of these novel findings, we aim to determine how glucose- and lipid-toxicity affect the ER export of protein cargo, particularly proinsulin, in beta cells and how defective ER export, in turn, contributes to ER stress and beta cell dysfunction. Over a thousand proteins, referred to as the proteostasis network, have been proposed to maintain ER homeostasis. However, to date, only a very small number of ER proteins have been investigated for their involvement in ER stress or proinsulin biogenesis in beta cells. A systematic proteomics analysis is needed to comprehensively understand how different diabetes-causing conditions perturb beta cell ER homeostasis at the onset of T2D. In this proposal, using systems biology approaches, we will test the central hypothesis that diabetogenic factors such as glucolipotoxicity disrupt beta cell ER function through perturbing ER protein homeostasis and COPII dependent ER export. There are two specific aims in this proposal: 1) Determine how COPII dependent ER export is regulated in health and diabetes; 2) Determine how ER chaperones and folding enzymes are altered in diabetes and how these changes affect beta cell ER export. This study will use state-of-the-art quantitative proteomics and other systems biology approaches to characterize the molecular mechanisms by which diabetes-causing conditions differentially alter ER homeostasis. The emphasis will be on the ER export, an under-investigated component of beta cell ER homeostasis.

Public Health Relevance

Beta cell ER dysfunction plays a critical role in the pathogenesis of both type 1 and type 2 diabetes which together affects about 25.8 million people in the United States. This study is expected to elucidate a novel mechanism underlying the impaired insulin biogenesis and beta cell failure in diabetes and provide novel therapeutic strategies, by targeting the ER co-chaperones and COPII dependent ER export, to alleviate chronic ER stress and associated loss of beta cell mass in diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK110314-04
Application #
9767125
Study Section
Molecular and Cellular Endocrinology Study Section (MCE)
Program Officer
Sechi, Salvatore
Project Start
2016-09-01
Project End
2021-08-31
Budget Start
2019-09-01
Budget End
2020-08-31
Support Year
4
Fiscal Year
2019
Total Cost
Indirect Cost
Name
Wayne State University
Department
Physiology
Type
Schools of Medicine
DUNS #
001962224
City
Detroit
State
MI
Country
United States
Zip Code
48202
Lee, Jin-Sook; Caruso, Joseph A; Hubbs, Garrett et al. (2018) Molecular architecture of mouse and human pancreatic zymogen granules: protein components and their copy numbers. Biophys Rep 4:94-103
Sameni, Mansoureh; Cavallo-Medved, Dora; Franco, Omar E et al. (2017) Pathomimetic avatars reveal divergent roles of microenvironment in invasive transition of ductal carcinoma in situ. Breast Cancer Res 19:56