Ric-8A-mediated stabilization of the trimeric G protein subunit Gαi is inhibited by pertussis toxin-catalyzed ADP-ribosylation
Ric-8A-mediated stabilization of the trimeric G protein subunit Gαi is inhibited by pertussis toxin-catalyzed ADP-ribosylation
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Ric-8A 介导的三聚体 G 蛋白亚基 Gαi 的稳定被百日咳毒素催化的 ADP 核糖基化抑制
DOI：
10.1016/j.bbrc.2017.01.036
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发表时间：
2017
影响因子：
3.1
通讯作者：
Hideki Sumimoto
中科院分区：
文献类型：
--
作者：
Kanako Chishiki;Sachiko Kamakura;Junya Hayase;Satoru Yuzawa;Hideki Sumimoto
异源三聚体G蛋白亚基Gαi可以被G蛋白偶联受体和胞质蛋白Ric-8A激活，后者也被认为可以阻止Gαi的泛素依赖性降解。在这里，我们表明，三个Gα i相关蛋白Gαi1，Gαi2和Gαi3的量，但不是Gαq的量，被百日咳毒素（PTX）处理的细胞迅速减少。这种减少似乎是由于Gαi的ADP-核糖基化，因为PTX处理不影响携带丙氨酸取代Cys 352的突变体Gαi2的量，Cys 352是被毒素ADP-核糖基化的残基。如用蛋白质合成抑制剂放线菌酮处理的细胞中所示，内源性和外源性Ric-8A的存在增加Gαi稳定性;然而，Ric-8A不能有效地稳定ADP-核糖基化Gαi。Ric-8A在体外和体内均不能与ADP核糖基化的Gαi结合。因此，PTX似乎至少部分地通过将Gαi转化为不稳定的ADP-核糖基化形式来发挥其病理作用，除了众所周知的ADP-核糖基化Gαi不能被G蛋白偶联受体触发的ATP信号之外。
The heterotrimeric G protein subunit Gαi can be activated by G protein-coupled receptors and the cytosolic protein Ric-8A, the latter of which is also known to prevent ubiquitin-dependent degradation of Gαi. Here we show that the amounts of the three Gαi-related proteins Gαi1, Gαi2, and Gαi3, but not that of Gαq, are rapidly decreased by cell treatment with pertussis toxin (PTX). The decrease appears to be due to ADP-ribosylation of Gαi, because PTX treatment does not affect the amount of a mutant Gαi2 carrying alanine substitution for Cys352, the residue that is ADP-ribosylated by the toxin. The presence of endogenous and exogenous Ric-8A increases Gαi stability as shown in cells treated with the protein synthesis inhibitor cycloheximide; however, Ric-8A fails to efficiently stabilize ADP-ribosylated Gαi. The failure agrees with the inability of Ric-8A to bind to ADP-ribosylated Gαi bothin vitroandin vivo. Thus PTX appears to exert its pathological effects at least in part by converting Gαi to an unstable ADP-ribosylated form, in addition to the well-known inability of ADP-ribosylated Gαi to transduce signals triggered by G protein-coupled receptors.