RT Journal Article
SR Electronic
T1 Long-Range Inhibitor-Induced Conformational Regulation of Human IRE1α Endoribonuclease Activity
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP mol.115.100917
DO 10.1124/mol.115.100917
A1 Nestor O Concha
A1 Angela Smallwood
A1 William Bonnette
A1 Rachel Totoritis
A1 Guofeng Zhang
A1 Kelly Federowicz
A1 Jingsong Yang
A1 Hongwei Qi
A1 Stephanie Chen
A1 Nino Campobasso
A1 Anthony E Choudhry
A1 Leanna E Shuster
A1 Karen A Evans
A1 Jeff Ralph
A1 Sharon Sweitzer
A1 Dirk A Heerding
A1 Carolyn A Buser
A1 Dai-shi Su
A1 Maurice P DeYoung
YR 2015
UL http://molpharm.aspetjournals.org/content/early/2015/10/05/mol.115.100917.abstract
AB Activation of the inositol-requiring enzyme-1 alpha (IRE1α) protein caused by endoplasmic reticulum (ER) stress results in the homodimerization of the N-terminal ER 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 XBP1 mRNA. Herein we report the first crystal structures of the cytoplasmic portion of a human phosphorylated IRE1α dimer in complex with GSK2850163, a novel, IRE1α-selective kinase inhibitor, and with staurosporine (STS), a broad spectrum kinase inhibitor. GSK2850163 inhibits both the kinase and RNAse activities of IRE1α. The inhibitor interacts with the catalytic residues Lys599 and Glu612 and displaces the kinase activation loop to the DFG-out conformation. Inactivation of IRE1α RNAse activity appears to be caused by a conformational change whereby the αC 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, STS binds at the ATP-binding site of IRE1α resulting in a dimer consistent with RNase active yeast Ire1 dimers. Activation of IRE1α 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.