Hemelaar Joris, Lelyveld Victor S, Kessler Benedikt M, Ploegh Hidde L
Department of Pathology, Harvard Medical School, Boston, Massachusetts 02115, USA.
J Biol Chem. 2003 Dec 19;278(51):51841-50. doi: 10.1074/jbc.M308762200. Epub 2003 Oct 6.
Apg8 is a ubiquitin-like protein involved in autophagy in yeast. Apg8 is covalently but transiently attached to membrane lipids through the actions of activating, conjugating, and processing/deconjugating enzymes. The mammalian Apg8 homologues GATE-16, GARARAP, and MAP1-LC3 have been implicated in intra-Golgi transport, receptor sorting, and autophagy, respectively. All are served by a single set of activating and conjugating enzymes. Here we identify a novel mammalian Apg8 homologue, which we name Apg8L, and describe the synthesis of electrophilic probes based on the GATE-16, GARARAP, MAP1-LC3, and Apg8L proteins. These probes not only form specific adducts in crude cell lysates, but also allow identification of the cellular proteases specific for the C termini of these Apg8 homologues. We find a single protease, Apg4B/autophagin-1, capable of acting on GATE-16, GABARAP, MAP1-LC3, and Apg8L. The Apg4B/autophagin-1 protease thus serves as a processing/deconjugating enzyme for these four highly divergent mammalian Apg8 homologues.
Apg8是一种参与酵母自噬的类泛素蛋白。Apg8通过激活、缀合和加工/去缀合酶的作用与膜脂共价但短暂地连接。哺乳动物的Apg8同源物GATE-16、GABARAP和MAP1-LC3分别与高尔基体内部运输、受体分选和自噬有关。所有这些都由一组单一的激活和缀合酶作用。在这里，我们鉴定出一种新的哺乳动物Apg8同源物，我们将其命名为Apg8L，并描述了基于GATE-16、GABARAP、MAP1-LC3和Apg8L蛋白的亲电探针的合成。这些探针不仅能在粗细胞裂解物中形成特异性加合物，还能鉴定出对这些Apg8同源物C末端具有特异性的细胞蛋白酶。我们发现一种单一的蛋白酶Apg4B/自噬相关蛋白1，能够作用于GATE-16、GABARAP、MAP1-LC3和Apg8L。因此，Apg4B/自噬相关蛋白1蛋白酶作为这四种高度不同的哺乳动物Apg8同源物的加工/去缀合酶。
