Mutation at the cargo-receptor binding site of Atg8 also affects its  general autophagy regulation function.
Autophagy is a highly conserved degradation pathway for intracellular macromolecules and organelles. Among those characterized autophagy regulators, the ubiquitin-like protein Atg8 is found to be a membrane modifier that both regulates biogenesis of transport vesicles and interacts with the cargo receptor Atg19 for selective autophagic transport of the vacuolar enzyme prApe1 in budding yeast. The role of Atg8 in the enlargement of vesicle membrane during autophagosome biogenesis has been well documented,but how Atg8 coordinates vesicle formation and sorting of selective cargo is largely unknown. Identification of the cargo-receptor binding site of Atg8 would provide information to solve this issue.Here we characterized Atg8 mutants that were defective in interaction with the prApe1 receptor Atg19 and found that the vesicle formation function of these Atg8 mutants was also compromised to different extents. Atg8 mutants with single-residue substitution at the Atg19-binding site were defective in lipid conjugation and/or subcellular localization. Additional Atg8 mutants were found defective in autophagosome formation without affecting their interaction with Atg19, suggesting partially overlapping of the cargo-sorting site and its domains critical for autophagy control. Our observation paves the road for a more comprehensive understanding on how Atg8 coordinates cargo sorting and vesicle formation in selective autophagic pathways.
Ho
Kung-Hsien
KH
Institution of Zoology, National Taiwan University, Taipei, Taiwan, Republic of China.
Chang
Hsiang-En
HE
Huang
Wei-Pang
WP
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000626:Aminopeptidases; D001343:Autophagy; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D001665:Binding Sites; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D011485:Protein Binding; D021381:Protein Transport; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment; D033921:Vesicular Transport Proteins / Q000737:chemistry / Q000378:metabolism*
C434480:ATG19 protein, S cerevisiae; C113757:ATG8 protein, S cerevisiae; D000071190:Autophagy-Related Protein 8 Family; D000071183:Autophagy-Related Proteins; D008869:Microtubule-Associated Proteins; D011956:Receptors, Cell Surface; D029701:Saccharomyces cerevisiae Proteins; D033921:Vesicular Transport Proteins; D000626:Aminopeptidases; C019689:APE1 protein, S cerevisiae