Atg8L/Apg8L is the fourth mammalian modifier of mammalian Atg8 conjugation mediated by human Atg4B, Atg7 and Atg3.
Murine Atg8L/Apg8L has significant homology with the other known mammalian Atg8 homologs, LC3, GABARAP and GATE-16. However, it is unclear whether murine Atg8L modification is mediated by human Atg4B, Atg7 and Atg3. Expression of Atg8L in HEK293 cells led to cleavage of its C-terminus. In vitro, the C-terminus of Atg8L was cleaved by human Atg4B, but not human Atg4A or Atg4C. Atg8L-I formed an E1-substrate intermediate with Atg7(C572S), and an E2-substrate intermediate with Atg3(C264S). A modified form of Atg8L was detected in the pelletable fraction in the presence of lysosomal protease inhibitors under nutrient-rich conditions. Cyan fluorescent protein (CFP)-Atg8L colocalized with yellow fluorescent protein (YFP)-LC3 in HeLa cells in the presence of the inhibitors. However, little accumulation of the modified form of Atg8L was observed under conditions of starvation. These results indicate that Atg8L is the fourth modifier of mammalian Atg8 conjugation.
Tanida
Isei
I
Molecular Cell Biology, Department of Biochemistry, Juntendo University School of Medicine, Tokyo, Japan.
Sou
Yu-shin
YS
Minematsu-Ikeguchi
Naoko
N
Ueno
Takashi
T
Kominami
Eiki
E
D000818:Animals; D000071193:Autophagy-Related Protein 7; D000071183:Autophagy-Related Proteins; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007668:Kidney; D051379:Mice; D008869:Microtubule-Associated Proteins; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000494:pharmacology; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D044764:Ubiquitin-Activating Enzymes / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism*; D014452:Ubiquitins / Q000502:physiology*
D000071183:Autophagy-Related Proteins; C480859:Gabarapl1 protein, mouse; D008869:Microtubule-Associated Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D014452:Ubiquitins; D044763:Ubiquitin-Conjugating Enzymes; C507524:ATG4B protein, human; D003546:Cysteine Endopeptidases; C509349:ATG7 protein, human; D000071193:Autophagy-Related Protein 7; D044764:Ubiquitin-Activating Enzymes; C455621:ATG3 protein, human