# Phosphoproteomic Analysis of Feedback Networks in T cell signaling

> **NIH NIH R01** · BROWN UNIVERSITY · 2020 · $408,047

## Abstract

Signaling networks are crucial for the orchestration of cellular functions in response to stimuli. Knowledge
of the structure of these networks provides a basis for understanding the pathological consequences of their
malfunction and offers opportunities for designing therapeutic interventions. The complexity of these networks
and the speed with which signals are transmitted in cells makes mapping them a formidable challenge. The
typical approach for elucidating the structure of cellular signaling networks involves an iterative process of
creating signaling protein disruptions, domain mutants and site-directed mutants followed by characterization
of each mutant through a battery of cellular activation assays. As a complementary approach, modern
proteomic methods using quantitative mass spectrometry can facilitate the hypothesis-driven characterization
of signaling pathways by providing a global view of cellular phosphorylation and protein-protein interactions
through a variety of activation states.
 T cells play a central role in cell-mediated immunity against viruses, a variety of microbes, and cancer.
This proposal focuses on the elucidation of the molecular details of the T cell signaling pathway using these
new technologies. Lck tyrosine kinase is the central regulator of T cell activation regulated through its
phosphorylation state. Lck autophosphorylation at Tyr394 activates the kinase, whereas phosphorylation at
Tyr505 inactivates the kinase. Four phosphatases were shown previously to act on Lck Tyr394, but how each
one is recruited to Lck and whether other negative regulatory molecules are involved is not understood. The
molecular mechanism controlling the proper distribution of Lck between the T cell receptor and downstream
signaling nodes such as the SLP76 scaffolded signalosome are not well defined. In the previous funding
period, our research team discovered that downstream members of the T cell signaling pathway regulate the
phosphorylation of Lck and its substrates. We discovered that the scaffold protein SLP-76 controls both
negative and positive feedback loops in T cell receptor signaling at Lck Tyr394. We also discovered that PLCγ1
regulates differential Lck substrate phosphorylation within the TCR and the SLP-76 complex.
 To gain new insights into the pathways regulating Lck activity and spatial localization, we have assembled
a multidisciplinary team to apply novel quantitative proteomic techniques, biochemical methods, and mouse
models to provide a detailed view of the network. The central question that we will address in this project is
how SLP76 and PLCγ1 set the spatial and temporal equilibrium of Lck activation resulting in appropriate T cell
response to antigen. Successful completion of the aims will clarify the identity of the regulatory proteins
employed in each feedback loop, define molecular factors controlling the cellular localization of Lck, and define
their physiological role.

## Key facts

- **NIH application ID:** 9915845
- **Project number:** 5R01AI083636-09
- **Recipient organization:** BROWN UNIVERSITY
- **Principal Investigator:** ARTHUR Robert SALOMON
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $408,047
- **Award type:** 5
- **Project period:** 2010-06-15 → 2022-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9915845

## Citation

> US National Institutes of Health, RePORTER application 9915845, Phosphoproteomic Analysis of Feedback Networks in T cell signaling (5R01AI083636-09). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9915845. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*