4yzd

Publication Abstract from PubMed

Activation of the inositol-requiring enzyme-1 alpha (IRE1alpha) protein caused by endoplasmic reticulum stress results in the homodimerization of the N-terminal endoplasmic reticulum luminal domains, autophosphorylation of the cytoplasmic kinase domains, and conformational changes to the cytoplasmic endoribonuclease (RNase) domains, which render them functional and can lead to the splicing of X-box binding protein 1 (XBP 1) mRNA. Herein, we report the first crystal structures of the cytoplasmic portion of a human phosphorylated IRE1alpha dimer in complex with (R)-2-(3,4-dichlorobenzyl)-N-(4-methylbenzyl)-2,7-diazaspiro(4.5)decane-7-carboxa mide, a novel, IRE1alpha-selective kinase inhibitor, and staurosporine, a broad spectrum kinase inhibitor. (R)-2-(3,4-dichlorobenzyl)-N-(4-methylbenzyl)-2,7-diazaspiro(4.5)decane-7-carboxa mide inhibits both the kinase and RNase activities of IRE1alpha. The inhibitor interacts with the catalytic residues Lys599 and Glu612 and displaces the kinase activation loop to the DFG-out conformation. Inactivation of IRE1alpha RNase activity appears to be caused by a conformational change, whereby the alphaC helix is displaced, resulting in the rearrangement of the kinase domain-dimer interface and a rotation of the RNase domains away from each other. In contrast, staurosporine binds at the ATP-binding site of IRE1alpha, resulting in a dimer consistent with RNase active yeast Ire1 dimers. Activation of IRE1alpha RNase activity appears to be promoted by a network of hydrogen bond interactions between highly conserved residues across the RNase dimer interface that place key catalytic residues poised for reaction. These data implicate that the intermolecular interactions between conserved residues in the RNase domain are required for activity, and that the disruption of these interactions can be achieved pharmacologically by small molecule kinase domain inhibitors.

Long-Range Inhibitor-Induced Conformational Regulation of Human IRE1alpha Endoribonuclease Activity.,Concha NO, Smallwood A, Bonnette W, Totoritis R, Zhang G, Federowicz K, Yang J, Qi H, Chen S, Campobasso N, Choudhry AE, Shuster LE, Evans KA, Ralph J, Sweitzer S, Heerding DA, Buser CA, Su DS, DeYoung MP Mol Pharmacol. 2015 Dec;88(6):1011-23. doi: 10.1124/mol.115.100917. Epub 2015 Oct, 5. PMID:26438213^[4]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.