The peptide hormone, insulin, regulates metabolism to homeostatically maintain blood glucose levels within a narrow physiological range. In pancreatic ss-cells, insulin is made and stored at high concentration within secretory granules. Physiological stimulation of insulin secretion (multiple times per day) requires very active synthesis of new insulin to replenish secretory granule reserves. Insulin synthesis begins with translation of preproinsulin for delivery into the lumen of the endoplasmic reticulum (ER). Therein, proinsulin must properly fold, which is easier than it sounds: proinsulin is a "disulfide-challenged" protein. Moreover, when beta cells are forced to synthesize higher levels of proinsulin than they are genetically-programmed to handle, they risk further proinsulin misfolding/disulfide mispairing, which leads to secretory pathway stress. The objective of this new grant cycle is to better understand proinsulin folding and export from the ER. We hypothesize that misfolding of a subfraction of proinsulin in the ER can block insulin production derived from the other subfracton of "bystander" proinsulin molecules, backlogging the protein in the ER, and driving ER stress, beta cell failure, loss of pancreatic insulin content, and diabetes. We propose four Specific Aims: 1) To elucidate the molecular mechanism(s) by which newly-described point mutations in the coding sequence of preproinsulin lead to human diabetes in neonates and adults. 2) To characterize ss-cell ER oxidoreductases. 3) To develop a new cell culture-based system to dissect steps leading to beta cell death. 4) To develop an in vivo analysis of pancreatic insulin production in diabetes.

Public Health Relevance

Insulin regulates metabolism to maintain normal blood glucose levels. Synthesis of new insulin begins with translation of proinsulin in the endoplasmic reticulum. In the past year, more than 20 new proinsulin mutations have been found to be associated with neonatal onset diabetes. Evidence suggests that these mutant proinsulins are made as proteins but it is not known how they cause diabetes. Each patient also havs another allele of perfectly normal proinsulin which should be more than enough proinsulin synthesis to satisfy the body's need for insulin. This new grant cycle proposes experiments to better understand proinsulin folding and export in order to see how misfolding of a subfraction of proinsulin in the ER can block insulin production derived from bystander proinsulin molecules, causing ER stress, beta cell failure, and diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK048280-20
Application #
8510627
Study Section
Molecular and Cellular Endocrinology Study Section (MCE)
Program Officer
Haft, Carol R
Project Start
1994-09-01
Project End
2014-05-31
Budget Start
2013-06-01
Budget End
2014-05-31
Support Year
20
Fiscal Year
2013
Total Cost
$481,261
Indirect Cost
$155,675
Name
University of Michigan Ann Arbor
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Haataja, Leena; Manickam, Nandini; Soliman, Ann et al. (2016) Disulfide Mispairing During Proinsulin Folding in the Endoplasmic Reticulum. Diabetes 65:1050-60
Alarcon, Cristina; Boland, Brandon B; Uchizono, Yuji et al. (2016) Pancreatic β-Cell Adaptive Plasticity in Obesity Increases Insulin Production but Adversely Affects Secretory Function. Diabetes 65:438-50
Zhu, Shuaishuai; Larkin, Dennis; Lu, Shusheng et al. (2016) Monitoring C-Peptide Storage and Secretion in Islet β-Cells In Vitro and In Vivo. Diabetes 65:699-709
Sharma, Rohit B; O'Donnell, Amy C; Stamateris, Rachel E et al. (2015) Insulin demand regulates β cell number via the unfolded protein response. J Clin Invest 125:3831-46
Cui, Jingqiu; Chen, Wei; Sun, Jinhong et al. (2015) Competitive Inhibition of the Endoplasmic Reticulum Signal Peptidase by Non-cleavable Mutant Preprotein Cargos. J Biol Chem 290:28131-40
Gao, Xing-Huang; Krokowski, Dawid; Guan, Bo-Jhih et al. (2015) Quantitative H2S-mediated protein sulfhydration reveals metabolic reprogramming during the integrated stress response. Elife 4:e10067
Alejandro, Emilyn U; Bozadjieva, Nadejda; Kumusoglu, Doga et al. (2015) Disruption of O-linked N-Acetylglucosamine Signaling Induces ER Stress and β Cell Failure. Cell Rep 13:2527-38
Russ, Holger A; Parent, Audrey V; Ringler, Jennifer J et al. (2015) Controlled induction of human pancreatic progenitors produces functional beta-like cells in vitro. EMBO J 34:1759-72
Liu, Ming; Sun, Jinhong; Cui, Jinqiu et al. (2015) INS-gene mutations: from genetics and beta cell biology to clinical disease. Mol Aspects Med 42:3-18
He, Kaiyu; Cunningham, Corey Nathaniel; Manickam, Nandini et al. (2015) PDI reductase acts on Akita mutant proinsulin to initiate retrotranslocation along the Hrd1/Sel1L-p97 axis. Mol Biol Cell 26:3413-23

Showing the most recent 10 out of 59 publications