TY - JOUR
T1 - Endoplasmic Reticulum Chaperone Glucose-Regulated Protein 94 Is Essential for Proinsulin Handling
AU - Ghiasi, Seyed Mojtaba
AU - Dahlby, Tina
AU - Hede Andersen, Caroline
AU - Haataja, Leena
AU - Petersen, Sólrun
AU - Omar-Hmeadi, Muhmmad
AU - Yang, Mingyu
AU - Pihl, Celina
AU - Bresson, Sophie Emilie
AU - Khilji, Muhammad Saad
AU - Klindt, Kristian
AU - Cheta, Oana
AU - Perone, Marcelo J
AU - Tyrberg, Björn
AU - Prats, Clara
AU - Barg, Sebastian
AU - Tengholm, Anders
AU - Arvan, Peter
AU - Mandrup-Poulsen, Thomas
AU - Marzec, Michal Tomasz
N1 - © 2019 by the American Diabetes Association.
PY - 2019/4
Y1 - 2019/4
N2 - Although endoplasmic reticulum (ER) chaperone binding to mutant proinsulin has been reported, the role of protein chaperones in the handling of wild-type proinsulin is underinvestigated. Here, we have explored the importance of glucose-regulated protein 94 (GRP94), a prominent ER chaperone known to fold insulin-like growth factors, in proinsulin handling within β-cells. We found that GRP94 coimmunoprecipitated with proinsulin and that inhibition of GRP94 function and/or expression reduced glucose-dependent insulin secretion, shortened proinsulin half-life, and lowered intracellular proinsulin and insulin levels. This phenotype was accompanied by post-ER proinsulin misprocessing and higher numbers of enlarged insulin granules that contained amorphic material with reduced immunogold staining for mature insulin. Insulin granule exocytosis was accelerated twofold, but the secreted insulin had diminished bioactivity. Moreover, GRP94 knockdown or knockout in β-cells selectively activated protein kinase R-like endoplasmic reticulum kinase (PERK), without increasing apoptosis levels. Finally, GRP94 mRNA was overexpressed in islets from patients with type 2 diabetes. We conclude that GRP94 is a chaperone crucial for proinsulin handling and insulin secretion.
AB - Although endoplasmic reticulum (ER) chaperone binding to mutant proinsulin has been reported, the role of protein chaperones in the handling of wild-type proinsulin is underinvestigated. Here, we have explored the importance of glucose-regulated protein 94 (GRP94), a prominent ER chaperone known to fold insulin-like growth factors, in proinsulin handling within β-cells. We found that GRP94 coimmunoprecipitated with proinsulin and that inhibition of GRP94 function and/or expression reduced glucose-dependent insulin secretion, shortened proinsulin half-life, and lowered intracellular proinsulin and insulin levels. This phenotype was accompanied by post-ER proinsulin misprocessing and higher numbers of enlarged insulin granules that contained amorphic material with reduced immunogold staining for mature insulin. Insulin granule exocytosis was accelerated twofold, but the secreted insulin had diminished bioactivity. Moreover, GRP94 knockdown or knockout in β-cells selectively activated protein kinase R-like endoplasmic reticulum kinase (PERK), without increasing apoptosis levels. Finally, GRP94 mRNA was overexpressed in islets from patients with type 2 diabetes. We conclude that GRP94 is a chaperone crucial for proinsulin handling and insulin secretion.
U2 - 10.2337/db18-0671
DO - 10.2337/db18-0671
M3 - Journal article
C2 - 30670477
VL - 68
SP - 747
EP - 760
JO - Diabetes
JF - Diabetes
SN - 0012-1797
IS - 4
ER -