The IRE1 interactome in human LS174T colon epithelial cells

ABSTRACT: Inositol-Requiring Enzyme (IRE)1 is an evolutionarily conserved sensor protein of the unfolded protein response (UPR). Vertebrates express two distinct paralogues: IRE1α (gene name ERN1) and IRE1β (gene name ERN2). Both proteins have a similar overall structure, with a sensor domain positioned in the endoplasmic reticulum (ER) lumen, and cytoplasmic kinase and endonuclease domains. For IRE1α, it is well-established that a protein folding chaperone called HSPA5 binds to the ER-luminal domain in conditions when the folding load and capacity are balanced. When unfolded proteins accumulate, HSPA5 is recruited to these unfolded proteins to aid in folding, thereby releasing IRE1α. This initiates a chain reaction of dimerization, trans-autophosphorylation and further oligomerization, resulting in an endonuclease-active IRE1α. Activated IRE1α cleaves an intron from the X-box binding protein 1 mRNA in an unusual cytoplasmic splicing reaction, and the resulting frameshift leads to production of a central UPR transcription factor, XBP1S. In contrast to this, IRE1β is far less extensively characterized. It is expressed solely in mucus-producing cells, more specifically goblet cells. Ectopic expression in other cell types such as Hela cells causes rapid cell death, most likely due to unregulated endonuclease activity. Upon aligning the two IRE1 paralogues, it becomes clear that the luminal domain has the lowest homology between the two paralogues, suggesting differences in how activity of either paralogue is tuned in the ER. In this project, we aimed to characterize and compare the IRE1β and IRE1α interactomes in LS174T cells, a cell line that has retained many goblet cell characteristics, to gain more insights into the regulation and downstream activity of IRE1β in a more relevant cellular background.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Epithelial Cell

SUBMITTER: Eva Cloots  

LAB HEAD: Sven Eyckerman

PROVIDER: PXD042756 | Pride | 2023-11-21

REPOSITORIES: Pride