Transport of phosphatidylinositol 3-phosphate into the vacuole via autophagic membranes in Saccharomyces cerevisiae.
Vps34, the sole PtdIns 3-kinase in yeast, is essential for autophagy. Here, we show that the lipid-kinase activity of Vps34 is required for autophagy, implying an essential role of its product PtdIns(3)P. The protein-kinase activity of Vps15, a regulatory subunit of the PtdIns 3-kinase complex, is also required for efficient autophagy. We monitored the distribution of PtdIns(3)P in living cells using a specific indicator, the 2xFYVE domain derived from mammalian Hrs. PtdIns(3)P was abundant at endosomes and on the vacuolar membrane during logarithmic growth phase. Under starvation conditions, we observed massive transport of PtdIns(3)P into the vacuole. This accumulation was dependent on the membrane dynamics of autophagy. Notably, PtdIns(3)P was highly enriched and delivered into the vacuole as a component of autophagosome membranes but not as a cargo enclosed within them, implying direct involvement of this phosphoinositide in autophagosome formation. We also found a possible enrichment of PtdIns(3)P on the inner autophagosomal membrane compared to the outer membrane. Based on these results we discuss the function of PtdIns(3)P in autophagy.
Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Keisuke
K
Obara
Takeshi
T
Noda
Kaori
K
Niimi
Yoshinori
Y
Ohsumi
D001343:Autophagy; D056827:Endosomal Sorting Complexes Required for Transport; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D058571:Vacuolar Sorting Protein VPS15; D014617:Vacuoles / Q000201:enzymology*
D056827:Endosomal Sorting Complexes Required for Transport; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D029701:Saccharomyces cerevisiae Proteins; D058571:Vacuolar Sorting Protein VPS15; C546854:VPS15 protein, S cerevisiae