# Phosphorylation of TSC2 (S1365) as a novel Regulator of mTORC1 Signaling in T Cells

> **NIH NIH R01** · JOHNS HOPKINS UNIVERSITY · 2021 · $536,289

## Abstract

PROJECT SUMMARY
 mTOR plays a critical role in integrating signals from the immune microenvironment to regulate T cell
activation, differentiation and function. We have been able to demonstrate that the Tuberous Sclerosis
Complex 2 (TSC2) protein plays an important role in regulating mTORC1 activation in T cells. TSC2 is a
RasGap protein that inhibits the activity of Rheb GTPase that in turn activates mTORC1. We have shown
that genetic deletion of TSC2 in T cells leads to enhanced mTORC1 activity and a marked increase in
CD8+ T cell effector function. However, while TSC2-/- T cells respond robustly to viruses and tumors, their
persistent mTORC1 activity leads to a decrease in memory CD8+ T cell generation. Recently, the Kass lab
has identified a novel phosphorylation site on TSC2 that regulates mTORC1 activity in cardiac myocytes.
Phosphorylation of this site (S1365) leads to the inhibition of mTORC1 signaling. Mutating this site(SA)
leads to an increase mTORC1 activity and the development of worse heart disease and mortality from
pressure-overload (PO) stress. Alternatively, creating a phosphomimetic (SE) at this site mitigates
mTORC1 activity and imparts protection from heart failure upon pressure overload. We hypothesized that
the TSC2 (S1365) site might play an important role in regulating mTORC1 activity in T cells. Our
preliminary studies demonstrate that upon TCR engagement this site is indeed phosphorylated. T cells
harboring the SA mutation have unaltered mTORC1 activity in the non-stimulated condition (unlike TSC2-/-
T cells), but show markedly increased activity upon TCR engagement. T cells with the SE mutation exhibit
the opposite. Furthermore, phosphorylation of TSC2 (S1365) is markedly induced by hypoxia, low pH and
reactive oxygen species suggesting that this pathway plays a critical role in integrating stress signals in
order to regulate T cell differentiation and function. In this project we seek to define and understand a novel
and selective mechanism of mTORC1 regulation in T cells. The overall goal of this proposal is to dissect
the mechanisms by which phosphorylation of TSC2 at S1365 regulates mTORC1 activation in T cells, and
consequently selectively regulates T cell activation, differentiation and function. Upon the completion of this
proposal our findings will help elucidate novel and critical mTORC1 regulatory signaling mechanisms in T
cells, and have implications for developing vaccines and engineering more robust T cells for Adoptive
Cellular Therapy. This may in turn result in improved treatment strategies for preventing and treating
infections as well as cancer.

## Key facts

- **NIH application ID:** 10111680
- **Project number:** 1R01AI156274-01
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** Erika L Pearce
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $536,289
- **Award type:** 1
- **Project period:** 2021-04-08 → 2026-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10111680

## Citation

> US National Institutes of Health, RePORTER application 10111680, Phosphorylation of TSC2 (S1365) as a novel Regulator of mTORC1 Signaling in T Cells (1R01AI156274-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10111680. Licensed CC0.

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