Human hAtg2A Protein Expressed in Yeast is Recruited to Preautophagosomal Structure but does not Complement Autophagy Defects of Atg2δ Strain

摘要

Yeast Atg2, an autophagy-related protein, is highly conservedin other fungi and has two homologues in humans,one of which is hAtg2A encoded by the hATG2A/KIAA0404 gene. Region of homology between Atg2 andhAtg2A proteins comprises the C-terminal domain. Weused yeast atg2? strain to express the GFP-KIAA0404gene, its fragment or fusions with yeast ATG2, and studytheir effects on autophagy. The GFP-hAtg2A protein localizedto punctate structures, some of which colocalizedwith Ape1-RFP-marked preautophagosomal structure(PAS), but it did not restore autophagy in atg2? cells.N-terminal fragment of Atg2 and N-terminal fragmentof hAtg2A were sufficient for PAS recruitment but werenot sufficient to function in autophagy. Neither a fusionof the N-terminal fragment of hAtg2A with C-terminaldomain of Atg2 nor a reciprocal fusion were functionalin autophagy. hAtg2A, in contrast to yeast Atg2, did notshow interaction with the yeast autophagy protein Atg9but both Atg2 proteins showed interaction with Atg18,a phospholipid-binding protein, in two-hybrid system.Moreover, deletion of ATG18 abrogated PAS recruitmentof hAtg2A. Our results show that human hAtg2A can notfunction in autophagy in yeast, however, it is recruitedto the PAS, possibly due to the interaction with Atg18.