ERp29 as a regulator of Insulin biosynthesis

PLoS One. 2020 May 20;15(5):e0233502. doi: 10.1371/journal.pone.0233502. eCollection 2020.

Abstract

The environment within the Endoplasmic Reticulum (ER) influences Insulin biogenesis. In particular, ER stress may contribute to the development of Type 2 Diabetes (T2D) and Cystic Fibrosis Related Diabetes (CFRD), where evidence of impaired Insulin processing, including elevated secreted Proinsulin/Insulin ratios, are observed. Our group has established the role of a novel ER chaperone ERp29 (ER protein of 29 kDa) in the biogenesis of the Epithelial Sodium Channel, ENaC. The biogenesis of Insulin and ENaC share may key features, including their potential association with COP II machinery, their cleavage into a more active form in the Golgi or later compartments, and their ability to bypass such cleavage and remain in a less active form. Given these similarities we hypothesized that ERp29 is a critical factor in promoting the efficient conversion of Proinsulin to Insulin. Here, we confirmed that Proinsulin associates with the COP II vesicle cargo recognition component, Sec24D. When Sec24D expression was decreased, we observed a corresponding decrease in whole cell Proinsulin levels. In addition, we found that Sec24D associates with ERp29 in co-precipitation experiments and that ERp29 associates with Proinsulin in co-precipitation experiments. When ERp29 was overexpressed, a corresponding increase in whole cell Proinsulin levels was observed, while depletion of ERp29 decreased whole cell Proinsulin levels. Together, these data suggest a potential role for ERp29 in regulating Insulin biosynthesis, perhaps in promoting the exit of Proinsulin from the ER via Sec24D/COPII vesicles.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • COP-Coated Vesicles / metabolism
  • Cystic Fibrosis / complications
  • Diabetes Mellitus, Type 2
  • Endoplasmic Reticulum / metabolism
  • Endoplasmic Reticulum Stress
  • Heat-Shock Proteins / physiology*
  • Humans
  • Insulin / biosynthesis*
  • Proinsulin / metabolism
  • Protein Transport
  • Vesicular Transport Proteins / metabolism*

Substances

  • ERP29 protein, human
  • Heat-Shock Proteins
  • Insulin
  • SEC24D protein, human
  • Vesicular Transport Proteins
  • Proinsulin