VAMP7 Regulates Autophagosome Formation by Supporting Atg9a Functions in Pancreatic β-Cells From Male Mice

Endocrinology. 2018 Nov 1;159(11):3674-3688. doi: 10.1210/en.2018-00447.

Abstract

Dysfunctional mitochondria are observed in β-cells of diabetic patients, which are eventually removed by autophagy. Vesicle-associated membrane protein (VAMP)7, a vesicular SNARE protein, regulates autophagosome formation to maintain mitochondrial homeostasis and control insulin secretion in pancreatic β-cells. However, its molecular mechanism is largely unknown. In this study, we investigated the molecular mechanism of VAMP7-dependent autophagosome formation using VAMP7-deficient β-cells and β-cell-derived Min6 cells. VAMP7 localized in autophagy-related (Atg)9a-resident vesicles of recycling endosomes (REs), which contributed to autophagosome formation, and it interacted with Hrb, Syntaxin16, and SNAP-47. Hrb recruited VAMP7 and Atg9a from the plasma membrane to REs. Syntaxin16 and SNAP-47 mediated autophagosome formation at a step later than the proper localization of VAMP7 to Atg9a-resident vesicles. Knockdown of Hrb, Syntaxin16, and SNAP-47 resulted in defective autophagosome formation, accumulation of dysfunctional mitochondria, and impairment of glucose-stimulated insulin secretion. Our data indicate that VAMP7 and Atg9a are initially recruited to REs to organize VAMP7 and Atg9a-resident vesicles in an Hrb-dependent manner. Additionally, VAMP7 forms a SNARE complex with Syntaxin16 and SNAP-47, which may cause fusions of Atg9a-resident vesicles during autophagosome formation. Thus, VAMP7 participates in autophagosome formation by supporting Atg9a functions that contribute to maintenance of mitochondrial quality.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Vesicular Transport / genetics
  • Animals
  • Autophagosomes / metabolism*
  • Autophagy / genetics
  • Autophagy-Related Proteins / genetics*
  • Autophagy-Related Proteins / metabolism
  • Endosomes / metabolism*
  • Gene Knockdown Techniques
  • Insulin Secretion
  • Insulin-Secreting Cells / metabolism*
  • Male
  • Membrane Fusion
  • Membrane Proteins / genetics*
  • Membrane Proteins / metabolism
  • Mice
  • Mice, Knockout
  • Mitochondria / metabolism*
  • Qb-SNARE Proteins / genetics
  • Qc-SNARE Proteins / genetics
  • R-SNARE Proteins / genetics*
  • R-SNARE Proteins / metabolism
  • Syntaxin 16 / genetics
  • Vesicular Transport Proteins / genetics*
  • Vesicular Transport Proteins / metabolism

Substances

  • Adaptor Proteins, Vesicular Transport
  • Agfg1 protein, mouse
  • Atg9A protein, mouse
  • Autophagy-Related Proteins
  • Membrane Proteins
  • Qb-SNARE Proteins
  • Qc-SNARE Proteins
  • R-SNARE Proteins
  • Snap47 protein, mouse
  • Sybl1 protein, mouse
  • Syntaxin 16
  • Vesicular Transport Proteins
  • syntaxin 16, mouse