Autophagy Defends Pancreatic β Cells From Human Islet Amyloid Polypeptide-Induced Toxicity

J Clin Invest. 2014 Aug;124(8):3489-500. doi: 10.1172/JCI71981. Epub 2014 Jul 18.

Abstract

Type 2 diabetes (T2D) is characterized by a deficiency in β cell mass, increased β cell apoptosis, and extracellular accumulation of islet amyloid derived from islet amyloid polypeptide (IAPP), which β cells coexpress with insulin. IAPP expression is increased in the context of insulin resistance, the major risk factor for developing T2D. Human IAPP is potentially toxic, especially as membrane-permeant oligomers, which have been observed to accumulate within β cells of patients with T2D and rodents expressing human IAPP. Here, we determined that β cell IAPP content is regulated by autophagy through p62-dependent lysosomal degradation. Induction of high levels of human IAPP in mouse β cells resulted in accumulation of this amyloidogenic protein as relatively inert fibrils within cytosolic p62-positive inclusions, which temporarily averts formation of toxic oligomers. Mice hemizygous for transgenic expression of human IAPP did not develop diabetes; however, loss of β cell-specific autophagy in these animals induced diabetes, which was attributable to accumulation of toxic human IAPP oligomers and loss of β cell mass. In human IAPP-expressing mice that lack β cell autophagy, increased oxidative damage and loss of an antioxidant-protective pathway appeared to contribute to increased β cell apoptosis. These findings indicate that autophagy/lysosomal degradation defends β cells against proteotoxicity induced by oligomerization-prone human IAPP.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / deficiency
  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism
  • Animals
  • Autophagy / physiology*
  • Diabetes Mellitus, Type 2 / pathology
  • Diabetes Mellitus, Type 2 / physiopathology
  • Heat-Shock Proteins / deficiency
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism
  • Humans
  • Insulin / metabolism
  • Insulin-Secreting Cells / pathology*
  • Insulin-Secreting Cells / physiology*
  • Islet Amyloid Polypeptide / chemistry
  • Islet Amyloid Polypeptide / genetics
  • Islet Amyloid Polypeptide / physiology*
  • Lysosomes / metabolism
  • Male
  • Mice
  • Mice, Knockout
  • Mice, Transgenic
  • NF-E2-Related Factor 2 / metabolism
  • Oxidative Stress
  • Protein Structure, Quaternary
  • Proteolysis
  • Rats
  • Rats, Transgenic
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequestosome-1 Protein

Substances

  • Adaptor Proteins, Signal Transducing
  • Heat-Shock Proteins
  • Insulin
  • Islet Amyloid Polypeptide
  • NF-E2-Related Factor 2
  • Nfe2l2 protein, mouse
  • Recombinant Proteins
  • Sequestosome-1 Protein
  • Sqstm1 protein, mouse