Characterization of mouse Ire1 alpha: cloning, mRNA localization in the brain and functional analysis in a neural cell line

In yeast, an endoplasmic reticulum (ER)-associated protein. Irelp, is belie ved to initiate the unfolded protein response (UPR), that is responsible fo r protein folding in the ER under stressed conditions. Two mammalian homolo gs of Irelp have been identified, Ire1 alpha and Irelp. We have previously reported that familial Alzheimer's disease linked presenilin-1 variants dow nregulate the signaling pathway of the UPR by affecting the phosphorylation of Ire1 alpha. In the present study, we cloned the mouse homolog of Ire1 a lpha for generating genetically modified mice. Ire1 alpha was ubiquitously expressed in all mouse tissues examined, and was expressed preferentially i n neuronal cells in mouse brain. This led us to investigate the effects of the downregulation of the UPR on the survival of neuronal cells under condi tions of ER stress. Morphological and biochemical studies using a dominant- negative form of mouse Ire1 alpha have revealed that cell death caused by E R stress can be attributed to apoptosis, and that the downregulation of the UPR enhances the apoptotic process in the mouse neuroblastoma cell Line, N euro2a. Our results indicate that genetically modified mice such as transge nic mice with a dominant-negative provide further understanding of the path ogenic mechanisms of Alzheimer's disease and other neurodegenerative disord ers. (C) 2000 Elsevier Science B.V. All rights reserved.