Pancreatic β cells overexpressing hIAPP impaired mitophagy and unbalanced mitochondrial dynamics

Cell Death Dis. 2018 May 1;9(5):481. doi: 10.1038/s41419-018-0533-x.

Abstract

Human islet amyloid polypeptide (hIAPP), or amylin, has the tendency to aggregate into insoluble amyloid fibrils, a typical feature of islets from type 2 diabetes individuals. Thus, we investigated comparatively the impact of hIAPP on key pathways involved in pancreatic beta survival. INS1E-hIAPP cells present a hyperactivation of MTORC1 and an inhibition of autophagy signaling, those cells showing an increase in cell size. Resveratrol, a MTORC1 inhibitor, can reverse TSC2 degradation that occurs in INS1E-hIAPP cells and diminished MTORC1 hyperactivation with concomitant autophagy stimulation. At the same time, a blockade in mitophagy was found in INS1E-hIAPP cells, as compared with control or INS1E-rIAPP cells. Consistently, human amylin overexpression generates a basal induction of nitrotyrosine levels and polyubiquitinated aggregates. Failure of the protein degradation machinery finally results in an accumulation of damaged and fissioned mitochondria, ROS production, and increased susceptibility to endoplasmic reticulum (ER)-stress-induced apoptosis. Overall, hIAPP overexpression in INS1E cells induced MTORC1 activation and mitophagy inhibition, favoring a pro-fission scenario of damaged mitochondria, these cells turn out to be more susceptible to the ER-stress-induced apoptosis and malfunction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Cell Line, Tumor
  • Endoplasmic Reticulum Stress
  • Humans
  • Insulin-Secreting Cells / metabolism*
  • Insulin-Secreting Cells / ultrastructure
  • Islet Amyloid Polypeptide / genetics
  • Islet Amyloid Polypeptide / metabolism*
  • Mechanistic Target of Rapamycin Complex 1 / metabolism
  • Mitochondria / metabolism*
  • Mitochondria / ultrastructure
  • Mitochondrial Dynamics*
  • Mitophagy*
  • Proteolysis
  • Rats
  • Reactive Oxygen Species / metabolism
  • Signal Transduction
  • Tuberous Sclerosis Complex 2 Protein / metabolism
  • Tyrosine / analogs & derivatives
  • Tyrosine / metabolism
  • Ubiquitination
  • Up-Regulation

Substances

  • Islet Amyloid Polypeptide
  • Reactive Oxygen Species
  • Tsc2 protein, rat
  • Tuberous Sclerosis Complex 2 Protein
  • 3-nitrotyrosine
  • Tyrosine
  • Mechanistic Target of Rapamycin Complex 1