Biology subjects

Grey, M. J.

Publications and source records attributed to Grey, M. J..

3 recordsLinked to original sources

bioRxiv2023

Structural basis for recognition of unfolded proteins by the ER stress sensor ERN1/IRE1α

IRE1 is an endoplasmic reticulum sensor that recognizes misfolded proteins to activate the unfolded protein response (UPR). We used cholera toxin (CTx), which activates IRE1 in cells, to understand how unfolded proteins are recognized. In vitro, the A1 subunit of CTx (CTxA1) bound IRE1 lumenal domain (IRE1LD). Global unfolding was not required. Instead, IRE1LD recognized a 7-residue motif within a metastable region of CTxA1 that was also found in microbial and host proteins involved in IRE1 activation. Binding mapped to a pocket on IRE1LD normally occupied by a segment of the IRE1 C-terminal flexible loop implicated in IRE1 regulation. Mutation of the recognition motif blocked CTx-induced IRE1 activation in live cells. These findings describe a mechanism for substrate recognition by IRE1 that induces the UPR.

cell biology↗

bioRxiv2021

The epithelial-specific ER stress sensor IRE1β enables host-microbiota crosstalk to affect colon goblet cell development

Epithelial cells lining mucosal surfaces of the gastrointestinal and respiratory tracts uniquely express IRE1{beta} (Ern2), a paralogue of the most evolutionarily conserved endoplasmic reticulum stress sensor IRE1. How IRE1{beta} functions at the host-environment interface and why a second IRE1 paralogue evolved remain incompletely understood. Using conventionally raised and germ-free Ern2-/- mice, we found that IRE1{beta} was required for microbiota-induced goblet cell maturation and mucus barrier assembly in the colon. This occurred only after colonization of the alimentary tract with normal gut microflora, which induced IRE1{beta} expression. IRE1{beta} acted by splicing Xbp1 mRNA to expand ER function and prevent ER stress in goblet cells. Although IRE1 can also splice Xbp1 mRNA, it did not act redundantly to IRE1{beta} in this context. By regulating assembly of the colon mucus layer, IRE1{beta} further shaped the composition of the gut microbiota. Mice lacking IRE1{beta} had a dysbiotic microbial community that failed to induce goblet cell development when transferred into germ-free wild type mice. These results show that IRE1{beta} evolved at mucosal surfaces to mediate crosstalk between gut microbes and the colonic epithelium required for normal homeostasis and host defense.

cell biology↗

bioRxiv2019

IRE1β negatively regulates IRE1α signaling in response to endoplasmic reticulum stress

IRE1{beta} is an ER stress sensor uniquely expressed in epithelial cells lining mucosal surfaces. Here, we show that intestinal epithelial cells expressing IRE1{beta} have an attenuated response to ER stress. IRE1{beta} assembles with and blocks activation of the closely related and most evolutionarily ancient stress-sensor IRE1 to suppress stress-induced xbp1 splicing, a key mediator of the unfolded protein response. In comparison, IRE1{beta} has weak xbp1 splicing activity, largely explained by a non-conserved amino acid in the kinase domain that impairs its phosphorylation and restricts oligomerization. This enables IRE1{beta} to act as a dominant negative suppressor of IRE1. The inhibitory effect is amplified in cells by disrupting an XBP1-dependent feedback loop regulating stress-induced expression of IRE1. Thus IRE1{beta} functions to negatively regulate IRE1 signaling, perhaps enabling intestinal epithelial cells to manage the response to chronic stress stimuli at the host-environment interface.

cell biology↗