The relevance of the phosphatidylinositolphosphat-binding motif FRRGT of Atg18 and Atg21 for the Cvt pathway and autophagy.
Atg18 and Atg21 are homologous S. cerevisiae autophagy proteins. Atg18 is essential for biogenesis of Cvt vesicles and autophagosomes, while Atg21 is only essential for Cvt vesicle formation. We found that mutated Atg18-(FTTGT), which lost almost completely its binding to PtdIns3P and PtdIns(3,5)P(2), is non-functional during the Cvt pathway but active during autophagy and pexophagy. Since the Cvt pathway does not depend on PtdIns(3,5)P(2), we conclude that the Cvt pathway requires binding of Atg18 to PtdIns3P. Mutated Atg21-(FTTGT) is inactive during the Cvt pathway but showed only partly reduced binding to PtdIns-phosphates, suggesting further lipid binding domains in Atg21. GFP-Atg18-(FTTGT) and Atg21-(FTTGT)-GFP are released from vacuolar punctae to the cytosol.
Krick
Roswitha
R
Center of Biochemistry and Molecular Cell Biology, Georg-August-University, Heinrich-Dueker-Weg 12, D-37073 Goettingen, Germany.
Tolstrup
Jörn
J
Appelles
Anika
A
Henke
Sandra
S
Thumm
Michael
M
D020816:Amino Acid Motifs; D001343:Autophagy; D000071183:Autophagy-Related Proteins; D001483:Base Sequence; D001665:Binding Sites; D017931:DNA Primers; D010450:Endopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050356:Lipid Metabolism; D008565:Membrane Proteins; D016297:Mutagenesis, Site-Directed; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism*; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
C441008:ATG18 protein, S cerevisiae; D000071183:Autophagy-Related Proteins; D017931:DNA Primers; D008565:Membrane Proteins; D018129:Phosphatidylinositol Phosphates; D029701:Saccharomyces cerevisiae Proteins; C450423:ATG21 protein, S cerevisiae; D010450:Endopeptidases