Sec16A is critical for both conventional and unconventional secretion of CFTR

Sci Rep. 2017 Jan 9;7:39887. doi: 10.1038/srep39887.

Abstract

CFTR is a transmembrane protein that reaches the cell surface via the conventional Golgi mediated secretion pathway. Interestingly, ER-to-Golgi blockade or ER stress induces alternative GRASP-mediated, Golgi-bypassing unconventional trafficking of wild-type CFTR and the disease-causing ΔF508-CFTR, which has folding and trafficking defects. Here, we show that Sec16A, the key regulator of conventional ER-to-Golgi transport, plays a critical role in the ER exit of protein cargos during unconventional secretion. In an initial gene silencing screen, Sec16A knockdown abolished the unconventional secretion of wild-type and ΔF508-CFTR induced by ER-to-Golgi blockade, whereas the knockdown of other COPII-related components did not. Notably, during unconventional secretion, Sec16A was redistributed to cell periphery and associated with GRASP55 in mammalian cells. Molecular and morphological analyses revealed that IRE1α-mediated signaling is an upstream regulator of Sec16A during ER-to-Golgi blockade or ER stress associated unconventional secretion. These findings highlight a novel function of Sec16A as an essential mediator of ER stress-associated unconventional secretion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cystic Fibrosis / genetics
  • Cystic Fibrosis / metabolism*
  • Cystic Fibrosis Transmembrane Conductance Regulator / genetics
  • Cystic Fibrosis Transmembrane Conductance Regulator / metabolism*
  • Endocytosis
  • Endoplasmic Reticulum / metabolism*
  • Endoplasmic Reticulum Stress / physiology*
  • Gene Knockdown Techniques
  • Golgi Apparatus / metabolism*
  • Golgi Matrix Proteins
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Membrane Proteins / metabolism
  • Mutation / genetics
  • Protein Transport
  • Secretory Pathway
  • Vesicular Transport Proteins / genetics
  • Vesicular Transport Proteins / metabolism*

Substances

  • GORASP2 protein, human
  • Golgi Matrix Proteins
  • Membrane Proteins
  • SEC16A protein, human
  • Vesicular Transport Proteins
  • cystic fibrosis transmembrane conductance regulator delta F508
  • Cystic Fibrosis Transmembrane Conductance Regulator