Affinity purification mass spectrometry analysis of PD-1 uncovers SAP as a new checkpoint inhibitor

Michael Peled, Anna S. Tocheva, Sabina Sandigursky, Shruti Nayak, Elliot A. Philips, Kim E. Nichols, Marianne Strazza, Inbar Azoulay-Alfaguter, Manor Askenazi, Benjamin G. Neel, Adam J. Pelzek, Beatrix Ueberheide, Adam Mor*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Programmed cell death-1 (PD-1) is an essential inhibitory receptor in T cells. Antibodies targeting PD-1 elicit durable clinical responses in patients with multiple tumor indications. Nevertheless, a significant proportion of patients do not respond to anti-PD-1 treatment, and a better understanding of the signaling pathways downstream of PD- 1 could provide biomarkers for those whose tumors respond and new therapeutic approaches for those whose tumors do not. We used affinity purificationmass spectrometry to uncover multiple proteins associated with PD-1. Among these proteins, signaling lymphocytic activation molecule-associated protein (SAP) was functionally and mechanistically analyzed for its contribution to PD-1 inhibitory responses. Silencing of SAP augmented and overexpression blocked PD-1 function. T cells from patients with X-linked lymphoproliferative disease (XLP), who lack functional SAP, were hyperresponsive to PD-1 signaling, confirming its inhibitory role downstream of PD-1. Strikingly, signaling downstream of PD-1 in purified T cell subsets did not correlate with PD-1 surface expression but was inversely correlated with intracellular SAP levels. Mechanistically, SAP opposed PD-1 function by acting as a molecular shield of key tyrosine residues that are targets for the tyrosine phosphatase SHP2, which mediates PD-1 inhibitory properties. Our results identify SAP as an inhibitor of PD-1 function and SHP2 as a potential therapeutic target in patients with XLP.

Original languageEnglish
Pages (from-to)E468-E477
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number3
DOIs
StatePublished - 16 Jan 2018
Externally publishedYes

Funding

FundersFunder number
NIH/National Cancer InstituteP30CA016087
National Institutes of HealthR01CA49152, 1R01AI125640-01
National Institute of Arthritis and Musculoskeletal and Skin DiseasesT32AR069515
School of Medicine, New York University
Rheumatology Research Foundation
New York University
Irma T. Hirschl Trust

    Keywords

    • PD-1
    • SAP
    • SHP2
    • T cells
    • XLP

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