Atg9 Trafficking in Autophagy-Related Pathways

Autophagy. May-Jun 2007;3(3):271-4. doi: 10.4161/auto.3912. Epub 2007 May 29.

Abstract

The origin of the autophagosomal membrane and the lipid delivery mechanism during autophagy remain unsolved mysteries. Some important hints to these questions come from Atg9, which is the only integral membrane protein required for autophagosome formation and considered a membrane carrier in autophagy-related pathways. In S. cerevisiae, Atg9 cycles between peripheral sites and the pre-autophagosomal structure/phagophore assembly site (PAS), the nucleating site for formation of the sequestering vesicle. We recently identified a peripheral membrane protein, Atg11, as a binding partner of Atg9, in a yeast two-hybrid screen. Based on our analysis we propose a model for Atg9 cycling. Our model suggests that a pool of Atg11 mediates the anterograde transport of Atg9 to the PAS along the actin cytoskeleton, and that this delivery process may serve as a membrane shuttle for vesicle assembly during yeast selective autophagy. Here, we discuss the implications of the model and present additional evidence that extends it with regard to membrane trafficking modes during pexophagy.

MeSH terms

  • Autophagy*
  • Autophagy-Related Proteins
  • Intracellular Membranes / metabolism
  • Membrane Proteins / metabolism*
  • Metabolic Networks and Pathways
  • Mitochondria / metabolism
  • Models, Biological
  • Phagosomes / metabolism
  • Protein Transport
  • Saccharomyces cerevisiae / cytology*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Vesicular Transport Proteins / metabolism

Substances

  • ATG9 protein, S cerevisiae
  • Atg11 protein, S cerevisiae
  • Autophagy-Related Proteins
  • Membrane Proteins
  • Saccharomyces cerevisiae Proteins
  • Vesicular Transport Proteins