Atg9 trafficking in the yeast Saccharomyces cerevisiae

Autophagy can be divided into selective and nonselective modes. This process is considered selective when a precise cargo is specifically and exclusively incorporated into autophagosomes, the double-membrane vesicles that are the hallmark of autophagy. In contrast, during nonselective, bulk autophagy, cytoplasmic components are randomly enwrapped into autophagosomes. To date, approximately 30 autophagy-related genes called ATG have been identified. Sixteen of them compose the general basic machinery catalyzing the formation of double-membrane vesicles in all eukaryotic cells. The rest of them are often not conserved between species and cooperate with the basic Atg proteins during either selective or nonselective autophagy.(1) Atg9 is the only integral membrane component of the conserved At9 machinery(2-4) and appears to be a crucial organizational element.(5) Recent studies in the S. cerevisiae have shown that Atg9 transport is clifferentially regulated depending on the autophagy mode.(6-8) In this addendum, we will review and discuss what has recently been unveiled about yeast S. cerevisioe Atg9 trafficking, its modulators and its potential role in double-membrane vesicle biogenesis.