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 4

CDA prevents dC-mediated PNPi resistance.

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CDA prevents dC-mediated PNPi resistance. (A) Cell Titer Glo analysis of...
(A) Cell Titer Glo analysis of CEM cells treated with 1 μM ulodesine (PNPi)/5 μM dG with or without 10 ng/ml recombinant cytidine deaminase (rCDA) in 1:1 base media to conditioned media (CM; n = 4). (B) Cell Titer Glo analysis of CEM-YFP and CEM-CDA cells treated with 5 μM dG and 1 μM PNPi with or without dC for 72 hours (n = 4; mean ± SD). (C) Stable isotope-labeled metabolite tracing and LC-MS/MS-MRM analysis of intracellular dNTP in CEM-YFP control or CEM-CDA cells treated for 24 hours with or without 1 μM PNPi in the presence of 1 g/L [13C6]glucose, 5 μM [15N3]dC, and 5 μM [15N5]dG. Bar color indicates metabolite isotopic composition and biosynthetic route by which it was formed (mean ± SD; n = 4). (D) μCT tumor volume analysis of PNPi response in NCG mice bearing bilateral CEM-YFP and CEM-CDA tumors treated with vehicle or PNPi (200 mg/kg, p.o. q.d.; mean ± SD; n = 8; 2-tailed Mann-Whitney test). (E) LC-MS/MS-MRM analysis of tumor interstitial fluid composition from the endpoint of experiment in D (n = 8; unpaired t test). CEM-YFP tumors were used for dG comparison, and vehicle-treated tumors were used for dC comparison. ****P < 0.0001.