Kageyama Takuya, Suzuki Kuninori, Ohsumi Yoshinori
Division of Molecular Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Biochem Biophys Res Commun. 2009 Jan 16;378(3):551-7. doi: 10.1016/j.bbrc.2008.11.084. Epub 2008 Dec 4.
Autophagy is a primarily non-selective degradation system of cytoplasmic constituents in lysosomes/vacuoles during starvation. In yeast, autophagy is also involved in the selective transport of Ape1, a vacuolar hydrolase, as a biosynthetic route. Ald6, a soluble cytoplasmic enzyme, is preferentially eliminated from cytoplasm via autophagy. However, little is known about the mechanisms of Ald6 targeting to autophagosomes. Here, we show that Lap3, a soluble cytosolic cysteine protease, is spatially associated with Ape1 and selectively transported to the vacuole during nitrogen starvation. The rate of Lap3 transport is much higher than that of Ald6 and is similar to that of Ape1. Moreover, ATG11 and ATG19, essential factors for Ape1 transport, are important for Lap3 transport. Most Lap3 is degraded within a couple of hours in the vacuole in contrast to Ape1; therefore, we conclude that the machinery required for Ape1 biosynthesis is used for selective degradation of Lap3.
自噬是饥饿期间溶酶体/液泡中细胞质成分的主要非选择性降解系统。在酵母中，自噬还参与作为生物合成途径的液泡水解酶Ape1的选择性运输。Ald6是一种可溶性细胞质酶，通过自噬优先从细胞质中清除。然而，关于Ald6靶向自噬体的机制知之甚少。在这里，我们表明，可溶性胞质半胱氨酸蛋白酶Lap3在空间上与Ape1相关联，并在氮饥饿期间选择性地运输到液泡中。Lap3的运输速率远高于Ald6，与Ape1相似。此外，Ape1运输的必需因子ATG11和ATG19对Lap3运输也很重要。与Ape1不同，大多数Lap3在液泡中几小时内就会降解；因此，我们得出结论，Ape1生物合成所需的机制用于Lap3的选择性降解。
