Quantitative phosphoproteomic analysis reveals involvement of PD-1 in multiple T cell functions

Anna S. Tocheva*, Michael Peled, Marianne Strazza, Kieran R. Adam, Shalom Lerrer, Shruti Nayak, Inbar Azoulay-Alfaguter, Connor J.R. Foster, Elliot A. Philips, Benjamin G. Neel, Beatrix Ueberheide, Adam Mor*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Programmed cell death protein 1 (PD-1) is a critical inhibitory receptor that limits excessive T cell responses. Cancer cells have evolved to evade these immunoregulatory mechanisms by upregulating PD-1 ligands and preventing T cell–mediated anti-tumor responses. Consequently, therapeutic blockade of PD-1 enhances T cell–mediated anti-tumor immunity, but many patients do not respond and a significant proportion develop inflammatory toxicities. To improve anti-cancer therapy, it is critical to reveal the mechanisms by which PD-1 regulates T cell responses. We performed global quantitative phosphoproteomic interrogation of PD-1 signaling in T cells. By complementing our analysis with functional validation assays, we show that PD-1 targets tyrosine phosphosites that mediate proximal T cell receptor signaling, cytoskeletal organization, and immune synapse formation. PD-1 ligation also led to differential phosphorylation of serine and threonine sites within proteins regulating T cell activation, gene expression, and protein translation. In silico predictions revealed that kinase/substrate relationships engaged downstream of PD-1 ligation. These insights uncover the phosphoproteomic landscape of PD-1–triggered pathways and reveal novel PD-1 substrates that modulate diverse T cell functions and may serve as future therapeutic targets. These data are a useful resource in the design of future PD-1–targeting therapeutic approaches.

Original languageEnglish
Pages (from-to)18036-18050
Number of pages15
JournalJournal of Biological Chemistry
Issue number52
StatePublished - 25 Dec 2020
Externally publishedYes


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