Purine nucleoside phosphorylase enables dual metabolic checkpoints that prevent T cell immunodeficiency and TLR7-associated autoimmunity
Evan R. Abt, … , Ting-Ting Wu, Caius G. Radu
Evan R. Abt, … , Ting-Ting Wu, Caius G. Radu
Published June 2, 2022
Citation Information: J Clin Invest. 2022;132(16):e160852. https://doi.org/10.1172/JCI160852.
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Research Article Immunology Metabolism

Purine nucleoside phosphorylase enables dual metabolic checkpoints that prevent T cell immunodeficiency and TLR7-associated autoimmunity

Abstract

Purine nucleoside phosphorylase (PNP) enables the breakdown and recycling of guanine nucleosides. PNP insufficiency in humans is paradoxically associated with both immunodeficiency and autoimmunity, but the mechanistic basis for these outcomes is incompletely understood. Here, we identify two immune lineage-dependent consequences of PNP inactivation dictated by distinct gene interactions. During T cell development, PNP inactivation is synthetically lethal with downregulation of the dNTP triphosphohydrolase SAMHD1. This interaction requires deoxycytidine kinase activity and is antagonized by microenvironmental deoxycytidine. In B lymphocytes and macrophages, PNP regulates Toll-like receptor 7 signaling by controlling the levels of its (deoxy)guanosine nucleoside ligands. Overriding this regulatory mechanism promotes germinal center formation in the absence of exogenous antigen and accelerates disease in a mouse model of autoimmunity. This work reveals that one purine metabolism gene protects against immunodeficiency and autoimmunity via independent mechanisms operating in distinct immune lineages and identifies PNP as a potentially novel metabolic immune checkpoint.

Authors

Evan R. Abt, Khalid Rashid, Thuc M. Le, Suwen Li, Hailey R. Lee, Vincent Lok, Luyi Li, Amanda L. Creech, Amanda N. Labora, Hanna K. Mandl, Alex K. Lam, Arthur Cho, Valerie Rezek, Nanping Wu, Gabriel Abril-Rodriguez, Ethan W. Rosser, Steven D. Mittelman, Willy Hugo, Thomas Mehrling, Shanta Bantia, Antoni Ribas, Timothy R. Donahue, Gay M. Crooks, Ting-Ting Wu, Caius G. Radu

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Figure 8

PNP inhibition promotes the germinal center reaction and accelerates autoimmunity.

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PNP inhibition promotes the germinal center reaction and accelerates aut...
(A) Flow cytometry analysis of spleen germinal center (GC) B cell and T follicular helper (Tfh) cell abundance in female BALB/c, C57BL/6, and NOD mice treated with or without 100 mg/kg ulodesine (PNPi; p.o.; q.d.) for 14 days (n = 4/group; 2-tailed Mann-Whitney test). (B) Spleen GC B cell and Tfh cell abundance in BALB/c mice treated with or without 100 mg/kg PNPi (q.d.) and 100 mg/kg (R)-DI-87 (dCKi; q.d.) for 14 days (n = 5/group; Kruskal-Wallis test with Dunn’s multiple comparisons correction). (C) RT-PCR analysis of C57BL/6 CD43– B cells stimulated with or without 1 μM PNPi, 5 μM dG/rG, and 1 μM dCKi in vitro for 4 hours (mean ± SD; n = 3; 1-way ANOVA corrected for multiple comparisons). (D) Analysis of female MRL-LPR mice treated with vehicle or PNPi ad libitum (20 mg/kg daily) for 35 days. Representative spleen ultrasound images and calculated volumes from day 35 analysis (mean ± SD; n = 4 vehicle; n = 5 PNPi; unpaired t test). (E) Analysis of spleens and inguinal lymph nodes (iLNs) from MRL-LPR mice treated with or without PNPi (mean ± SD; n = 4 vehicle; n = 5 PNPi; unpaired t test). (F) Total urine protein levels from MRL-LPR mice treated with or without PNPi (mean ± SD; unpaired t test). (G) Representative kidney H&E immunohistochemistry analysis of MRL-LPR mice treated with or without PNPi. Scale bar: 50 μm. (H) Luminex serum cytokine analysis of MRL-LPR mice treated with or without PNPi. (I) Flow cytometry analysis of splenic CD19+ B cells from MRL-LPR mice treated with or without PNPi (mean ± SD; n = 3–4; unpaired t test). *P < 0.05; **P < 0.01; ****P < 0.0001.