Xia Pengyan, Wang Shuo, Huang Guanling, Du Ying, Zhu Pingping, Li Man, Fan Zusen
1] Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China [2] University of Chinese Academy of Sciences, Beijing 100049, China.
Key Laboratory of Infection and Immunity of CAS, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
Cell Res. 2014 Aug;24(8):943-58. doi: 10.1038/cr.2014.85. Epub 2014 Jul 1.
WASH (Wiskott-Aldrich syndrome protein (WASP) and SCAR homolog) was identified to function in endosomal sorting via Arp2/3 activation. We previously demonstrated that WASH is a new interactor of BECN1 and present in the BECN1-PIK3C3 complex with AMBRA1. The AMBRA1-DDB1-CUL4A complex is an E3 ligase for K63-linked ubiquitination of BECN1, which is required for starvation-induced autophagy. WASH suppresses autophagy by inhibition of BECN1 ubiquitination. However, how AMBRA1 is regulated during autophagy remains elusive. Here, we found that RNF2 associates with AMBRA1 to act as an E3 ligase to ubiquitinate AMBRA1 via K48 linkage. RNF2 mediates ubiquitination of AMBRA1 at lysine 45. Notably, RNF2 deficiency enhances autophagy induction. Upon autophagy induction, RNF2 potentiates AMBRA1 degradation with the help of WASH. WASH deficiency impairs the association of RNF2 with AMBRA1 to impede AMBRA1 degradation. Our findings reveal another novel layer of regulation of autophagy through WASH recruitment of RNF2 for AMBRA1 degradation leading to downregulation of autophagy.
WASH（威斯科特-奥尔德里奇综合征蛋白（WASP）和SCAR同源物）被确定通过激活Arp2/3在内体分选过程中发挥作用。我们之前证明WASH是BECN1的新相互作用蛋白，并与AMBRA1一起存在于BECN1-PIK3C3复合物中。AMBRA1-DDB1-CUL4A复合物是一种E3连接酶，负责BECN1的K63连接泛素化，这是饥饿诱导自噬所必需的。WASH通过抑制BECN1的泛素化来抑制自噬。然而，AMBRA1在自噬过程中是如何被调控的仍不清楚。在这里，我们发现RNF2与AMBRA1结合，作为一种E3连接酶通过K48连接对AMBRA1进行泛素化。RNF2介导AMBRA1赖氨酸45位点的泛素化。值得注意的是，RNF2缺陷增强了自噬诱导。在自噬诱导时，RNF2在WASH的帮助下增强AMBRA1的降解。WASH缺陷会损害RNF2与AMBRA1的结合，从而阻碍AMBRA1的降解。我们的研究结果揭示了自噬调控的另一个新层面，即通过WASH招募RNF2来降解AMBRA1，从而导致自噬下调。
