The molecular basis for selective inhibition of unconventional mRNA splicing by an IRE1-binding small molecule
The molecular basis for selective inhibition of unconventional mRNA splicing by an IRE1-binding small molecule
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DOI：
10.1073/pnas.1115623109
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发表时间：
2012-04-10
影响因子：
11.1
通讯作者：
Harding, Heather P.
中科院分区：
文献类型：
--
作者：
Cross, Benedict C. S.;Bond, Peter J.;Harding, Heather P.
IRE1将内质网未折叠蛋白负载与RNA切割事件偶联，最终导致Xbp1 mRNA的序列特异性剪接和多种膜结合mRNA的调节性降解。我们报告的小分子抑制剂，达到其选择性的识别，形成一个异常稳定的席夫碱与赖氨酸907在IRE1核酸内切酶结构域，在酶抑制剂复合物中的亚胺键的溶剂难接近性解释。该抑制剂（缩写为4 μ 8C）阻断底物进入IRE1的活性位点，并选择性地使Xbp1剪接和IRE1介导的mRNA降解失活。令人惊讶的是，抑制IRE1核酸内切酶活性不会使细胞对急性内质网应激的后果敏感，而是干扰分泌能力的扩增。因此，IRE1的核酸内切酶活性位点中的独特残基的化学反应性和空间位阻可以被选择性抑制剂利用以干扰病理环境中的蛋白质分泌。
IRE1 couples endoplasmic reticulum unfolded protein load to RNA cleavage events that culminate in the sequence-specific splicing of the Xbp1 mRNA and in the regulated degradation of diverse membrane-bound mRNAs. We report on the identification of a small molecule inhibitor that attains its selectivity by forming an unusually stable Schiff base with lysine 907 in the IRE1 endonuclease domain, explained by solvent inaccessibility of the imine bond in the enzyme-inhibitor complex. The inhibitor ( abbreviated 4 mu 8C) blocks substrate access to the active site of IRE1 and selectively inactivates both Xbp1 splicing and IRE1-mediated mRNA degradation. Surprisingly, inhibition of IRE1 endonuclease activity does not sensitize cells to the consequences of acute endoplasmic reticulum stress, but rather interferes with the expansion of secretory capacity. Thus, the chemical reactivity and sterics of a unique residue in the endonuclease active site of IRE1 can be exploited by selective inhibitors to interfere with protein secretion in pathological settings.