Regulation of Signal Transduction by Enzymatically Inactive Antiviral RNA Helicase Proteins MDA5, RIG-I, and LGP2
Regulation of Signal Transduction by Enzymatically Inactive Antiviral RNA Helicase Proteins MDA5, RIG-I, and LGP2
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DOI：
10.1074/jbc.m807365200
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发表时间：
2009-04-10
影响因子：
4.8
通讯作者：
Horvath, Curt M.
中科院分区：
文献类型：
--
作者：
Bamming, Darja;Horvath, Curt M.
细胞内模式识别受体MDA 5、RIG-I和LGP 2是细胞对病毒感染应答的必要组分，并且与RNA解旋酶的DEXH盒亚家族同源。然而，解旋酶活性在干扰素产生的调节中的相关性仍然难以捉摸。为了研究解旋酶结构域功能对这些信号传导蛋白的重要性，分析了针对保守解旋酶序列基序的一系列突变的酶活性、RNA结合、干扰素诱导和抗病毒信号传导。结果表明，所有的目标图案所需的ATP水解，但一个子集参与RNA结合。酶失活突变体的信号传导能力不同。值得注意的是，MDA 5基序I、III和VI以及RIG-I基序III的突变产生具有组成性抗病毒活性的解旋酶蛋白，而RIG-I基序V的突变保留ATP水解，但不能介导信号转导。这些发现表明，I型干扰素生产介导的全长MDA 5和RIG-I是独立的解旋酶结构域催化活性。此外，LGP 2对抗病毒信号的负调节既不需要酶活性，也不需要RNA结合，这支持了RNA非依赖性干扰机制。
Intracellular pattern recognition receptors MDA5, RIG-I, and LGP2 are essential components of the cellular response to virus infection and are homologous to the DEXH box subfamily of RNA helicases. However, the relevance of helicase activity in the regulation of interferon production remains elusive. To examine the importance of the helicase domain function for these signaling proteins, a series of mutations targeting conserved helicase sequence motifs were analyzed for enzymatic activity, RNA binding, interferon induction, and antiviral signaling. Results indicate that all targeted motifs are required for ATP hydrolysis, but a subset is involved in RNA binding. The enzymatically inactive mutants differed in their signaling ability. Notably, mutations to MDA5 motifs I, III, and VI and RIG-I motif III produced helicase proteins with constitutive antiviral activity, whereas mutations in RIG-I motif V retained ATP hydrolysis but failed to mediate signal transduction. These findings demonstrate that type I interferon production mediated by full-length MDA5 and RIG-I is independent of the helicase domain catalytic activity. In addition, neither enzymatic activity nor RNA binding was required for negative regulation of antiviral signaling by LGP2, supporting an RNA-independent interference mechanism.