Phosphorylation of IRE1 at S729 regulates RIDD in B cells and antibody production after immunization

• Published in: The Journal of cell biology Vol. 217; no. 5; pp. 1739 - 1755
• Main Authors: Tang, Chih-Hang Anthony, Chang, Shiun, Paton, Adrienne W., Paton, James C., Gabrilovich, Dmitry I., Ploegh, Hidde L., Del Valle, Juan R., Hu, Chih-Chi Andrew
• Format: Journal Article
• Language: English
• Published: United States Rockefeller University Press 07.05.2018
• Subjects: Amino Acid Sequence; Animals; Antibody Formation; B-Lymphocytes - metabolism; Dithiothreitol - pharmacology; Endoplasmic reticulum; Endoplasmic Reticulum Stress - drug effects; Immunization; Immunoglobulin G - blood; Immunoglobulin M - blood; Immunoglobulins; Lipopolysaccharides; Lymphocytes B; Membrane Proteins - chemistry; Membrane Proteins - metabolism; Mice; Mice, Inbred C57BL; Models, Animal; Models, Biological; mRNA; Pharmacology; Phosphorylation; Phosphoserine - metabolism; Protein-Serine-Threonine Kinases - chemistry; Protein-Serine-Threonine Kinases - metabolism; Ribonucleic acid; RNA; RNA Stability; Stresses; Subtilase; Switches; T-Lymphocytes - metabolism; Toll-like receptors; Up-Regulation - drug effects; X-Box Binding Protein 1 - metabolism
• ISSN: 0021-9525; 1540-8140; 1540-8140
• DOI: 10.1083/jcb.201709137

To relieve endoplasmic reticulum (ER) stress, IRE1 splices XBP1 messenger RNA (mRNA) or engages regulated IRE1-dependent decay (RIDD) of other mRNAs. Upon XBP1 deficiency, IRE1 switches to perform RIDD. We examined IRE1 in XBP1-deficient B cells and discovered that IRE1 undergoes phosphorylation at S729. We generated an anti–phospho-S729 antibody to investigate such phosphorylation. Compared with pharmacological ER stress inducers or Toll-like receptor ligands, the bacterial subtilase cytotoxin has an unusual capability in causing rapid and strong phosphorylation at S729 and triggering B cells to express spliced XBP1. To assess the function of S729 in IRE1, we generated S729A knock-in mice and found S729 is critically important for lipopolysaccharide-stimulated plasmablasts to respond to additional ER stress and for antibody production in response to immunization. We further crossed mice carrying an S729A mutation or ΔIRE1 (missing the kinase domain) with B cell–specific XBP1-deficient mice to trigger RIDD and discovered a critical role for S729 in regulating RIDD in B cells.