Atg9 is the only essential transmembrane protein involved in cellular autophagy. Autophagy regulates cellular homeostasis by allowing the turnover and recycling of misfolded proteins and damaged organelles. Formation of the double-membrane isolation membrane that forms the pre-autophagosome requires the contribution of highly mobile cytoplasmic vesicles containing Atg9. These vesicles are derived from recycling endosomes and are responsible for recruiting and delivering lipid components to the assembling autophagosome.
