# Dissecting the pathways controlling tunable responses to TCR signaling

> **NIH NIH R01** · UNIVERSITY OF COLORADO DENVER · 2020 · $29,854

## Abstract

Dissecting the pathways controlling tunable responses to TCR signaling
Summary
Stimulation of the T-cell receptor (TCR) leads to activation, a process that includes changes in T cell
metabolism, survival, proliferation, cytokine responsiveness, migration behavior, and effector
functions. Life versus death, as well as lineage decisions of T cells are determined in large part by the
strength of TCR signaling. Our previous studies have demonstrated that the transcription factor IRF4
is upregulated by TCR stimulation in CD8 T cells, and that the maximum level of IRF4 achieved is
dependent on the strength of TCR signaling via the Tec kinase ITK. In turn, IRF4 promotes T cell
differentiation into massively proliferating antiviral effector cells in a dose-dependent manner. Yet,
mechanistic insight into how TCR stimulation produces a dynamic range of responses defined by
distinct gene expression patterns is currently lacking. Our preliminary studies indicate that the Tec
kinase ITK is a focal point for the tunable component of TCR signaling. Previous studies showed that
ITK is not required for all TCR signaling; instead, in its absence, TCR signaling is significantly
reduced. From these studies, the clear function of ITK was difficult to discern, as some aspects of T
cell activation appeared normal in the absence of ITK, whereas other T cell functions were greatly
impaired. Our current data, using IRF4 upregulation as an example of TCR tuning, provide a
framework to understand these apparent discrepancies. These studies have revealed that variations
in antigen density and in TCR affinity can modulate gene expression patterns shortly after activation
of naive CD8 T cells. Dissecting these pathways shows that the two second messengers generated
by activation of phospholipase C-γ, the major substrate of ITK, cooperate to regulate all-or-nothing
(digital) versus graded (analog) responses to changes in TCR signal strength. The relative balance
of these differing inputs determines which responses exhibit the broadest range of tunability to TCR
signaling. Based on these data, we hypothesize that the magnitude of ITK activity is determined by
the multiplicity of ITAM phosphorylation at the TCR, and that variations in ITK activity tune the
calcium response that regulates transcription factor activation. Further, we propose that ITK-
dependent tuning of TCR signal strength controls a program of gene expression that is established
within hours after TCR stimulation, and thus impacts the differentiation pathways of activated cells.
To test these hypotheses, we propose to determine how variations in TCR signal strength lead to
graded versus digital expression of entire programs of gene expression at the global and single cell
level, and how these patterns are established by the first wave of transcriptional activation following T
cell stimulation. We will also assess whether the magnitude of ITAM phosphorylation regulates the
dynamic range of ITK-dependent TCR signal...

## Key facts

- **NIH application ID:** 10074912
- **Project number:** 3R01AI132419-04S1
- **Recipient organization:** UNIVERSITY OF COLORADO DENVER
- **Principal Investigator:** LESLIE JOAN BERG
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $29,854
- **Award type:** 3
- **Project period:** 2018-01-24 → 2022-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10074912

## Citation

> US National Institutes of Health, RePORTER application 10074912, Dissecting the pathways controlling tunable responses to TCR signaling (3R01AI132419-04S1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10074912. Licensed CC0.

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