Combined immunodeficiency due to a mutation in the γ1 subunit of the coat protein I complex
Wayne Bainter, … , Victor W. Hsu, Raif S. Geha
Wayne Bainter, … , Victor W. Hsu, Raif S. Geha
Published February 1, 2021
Citation Information: J Clin Invest. 2021;131(3):e140494. https://doi.org/10.1172/JCI140494.
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Research Article Immunology

Combined immunodeficiency due to a mutation in the γ1 subunit of the coat protein I complex

Abstract

The coat protein I (COPI) complex mediates retrograde trafficking from the Golgi to the endoplasmic reticulum (ER). Five siblings with persistent bacterial and viral infections and defective humoral and cellular immunity had a homozygous p.K652E mutation in the γ1 subunit of COPI (γ1-COP). The mutation disrupts COPI binding to the KDEL receptor and impairs the retrieval of KDEL-bearing chaperones from the Golgi to the ER. Homozygous Copg1K652E mice had increased ER stress in activated T and B cells, poor antibody responses, and normal numbers of T cells that proliferated normally, but underwent increased apoptosis upon activation. Exposure of the mutants to pet store mice caused weight loss, lymphopenia, and defective T cell proliferation that recapitulated the findings in the patients. The ER stress-relieving agent tauroursodeoxycholic acid corrected the immune defects of the mutants and reversed the phenotype they acquired following exposure to pet store mice. This study establishes the role of γ1-COP in the ER retrieval of KDEL-bearing chaperones and thereby the importance of ER homeostasis in adaptive immunity.

Authors

Wayne Bainter, Craig D. Platt, Seung-Yeol Park, Kelsey Stafstrom, Jacqueline G. Wallace, Zachary T. Peters, Michel J. Massaad, Michel Becuwe, Sandra Andrea Salinas, Jennifer Jones, Sarah Beaussant-Cohen, Faris Jaber, Jia-Shu Yang, Tobias C. Walther, Jordan S. Orange, Chitong Rao, Seth Rakoff-Nahoum, Maria Tsokos, Shafiq Ur Rehman Naseem, Salem Al-Tamemi, Janet Chou, Victor W. Hsu, Raif S. Geha

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Figure 3

Activated B cells from homozygous Copg1K652E mutant mice have mislocalized BiP and increased ER stress.

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Activated B cells from homozygous Copg1K652E mutant mice have mislocaliz...
(A) Representative images of LPS+IL-4 stimulated B cells from mutant mice and controls stained for the ER marker calnexin (red) and BiP (green) and merged (yellow) (left). Scale bars: 2 μM. Quantitation of colocalization of calnexin and BiP (right) with a representative result from 3 independent experiments shown. n = 3 cells examined in each. (B) Representative images of B cells from the same experiment in A, stained for the Golgi marker GM130 (red) and BiP (green) and merged (yellow) (left). Scale bars: 2 μM. Quantitation of colocalization of GM130 and BiP (right) with a representative result from 3 independent experiments shown. n = 3 cells examined in each. (C) Quantitation of colocalization of calreticulin and PDI with calnexin and with GM130 in LPS+IL-4 stimulated B cells from mutant mice and WT controls. (D) Relative mRNA expression of the UPR response genes Xbp1, sXbp1, and Ddit3 in unstimulated and LPS+IL-4 stimulated B cells from mutant mice and WT controls. n = 3 independent experiments each with 5 mice per group. (E) Relative Hspa5 and Dock8 mRNA expression. n = 3 independent experiments each with 3 mice per group. (F) Representative immunoblot of BiP and DOCK8 in unstimulated and LPS+IL-4 stimulated B cells from mutant mice and WT controls and quantitative analysis of the results of BiP or DOCK8 expression relative to WT control from 3 experiments with 3 mice per group. (G) Representative histogram analysis of ER-Tracker dye uptake by unstimulated and LPS+IL-4 stimulated mutant and WT B cells (left) and quantitation of MFI of ER-Tracker dye in 4 experiments each with 3 mice/group (right). Columns and bars represent mean ± SEM. *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001; ****P ≤ 0.0001, 2-tailed Student’s t test.