Atg11 Links Cargo to the Vesicle-forming Machinery in the Cytoplasm to Vacuole Targeting Pathway

Abstract

Proteins are selectively packaged into vesicles at specific sites and then delivered correctly to the various organelles where they function, which is critical to the proper physiology of each organelle. The precursor form of the vacuolar hydrolase aminopeptidase I is a selective cargo molecule of the cytoplasm to vacuole targeting (Cvt) pathway and autophagy. Precursor Ape1 along with its receptor Atg19 forms the Cvt complex, which is transported to the pre-autophagosomal structure (PAS), the putative site of Cvt vesicle formation, in a process dependent on Atg11. Here, we show that this interaction occurs through the Atg11 C terminus; subsequent recruitment of the Cvt complex to the PAS depends on central regions within Atg11. Atg11 was shown to physically link several proteins, although the timing of these interactions and their importance are unknown. Our mapping shows that the Atg11 coiled-coil domains are involved in self-assembly and the interaction with other proteins, including two previously unidentified partners, Atg17 and Atg20. Atg11 mutants defective in the transport of the Cvt complex to the PAS affect the localization of other Atg components, supporting the idea that the cargo facilitates the organization of the PAS in selective autophagy. These findings suggest that Atg11 plays an integral role in connecting cargo molecules with components of the vesicle-forming machinery.