# TGF-β Regulates CD8+ T Cell Memory by Triggering mTORC1Weak-Mediated Activation of the Transcriptional FOXO1-TCF1-Eomes and Metabolic AMPK-ULK1-ATG7 Pathways

## TL;DR

TGF-β helps create long-lasting CD8+ memory T cells by activating specific transcription and metabolic pathways, which could improve vaccines for cancer and infectious diseases.

## Contribution

This study reveals a novel mechanism by which TGF-β regulates CD8+ T cell memory through mTORC1Weak-mediated activation of FOXO1-TCF1-Eomes and AMPK-ULK1-ATG7 pathways.

## Key findings

- TGF-β triggers weak mTORC1 signaling, which activates transcriptional factors like FOXO1, TCF1, and Eomes.
- TGF-β promotes metabolic changes involving AMPK-ULK1-ATG7 pathways and fatty acid oxidation in CD8+ memory T cells.
- TGF-β-induced CD8+ memory T cells show enhanced survival and mitochondrial mass.

## Abstract

What are the main findings?
TGF-β functions as an antagonist of mTORC1 activation.TGF-β regulates CD8+ T cell memory via the transcriptional FOXO1-TCF1-Eomes and metabolic AMPK-ULK1-ATG7 pathways.

TGF-β functions as an antagonist of mTORC1 activation.

TGF-β regulates CD8+ T cell memory via the transcriptional FOXO1-TCF1-Eomes and metabolic AMPK-ULK1-ATG7 pathways.

What are the implications of the main findings?
The Smad-independent TGF-β signaling pathway plays an important role in controlling T cell immunity.TGF-β-related signaling is a critical node to target for the development of novel vaccines for the treatment of cancer and infectious diseases.

The Smad-independent TGF-β signaling pathway plays an important role in controlling T cell immunity.

TGF-β-related signaling is a critical node to target for the development of novel vaccines for the treatment of cancer and infectious diseases.

CD8+ memory T (TM) cells are essential for vaccine-induced protective immunity. While transforming growth factor beta (TGF-β) triggers CD8+ TM cell differentiation, the underlying molecular mechanism(s) has yet to be uncovered. We therefore used a well-established cell culture protocol to prepare TGF-β-triggered CD8+ TM cells derived from chicken ovalbumin (OVA)-specific T cell receptor (TCR) transgenic OTI mice, and systematically characterized them using Western blotting, confocal microscopy, flow cytometry and Seahorse assay analyses. We found that TGF-β/T cells exhibit a TM cell phenotype (CD62L+KLRG1−) and display long-term survival upon adoptive transfer into mice. To elucidate the signaling circuitry underpinning the observed transcriptional and metabolic changes required to promote CD8+ TM cell differentiation, we measured the expression of several critical factors and found that TGF-β triggered weak mTORC1 (mTORC1Weak) signaling. mTORC1Weak signaling in turn led to an increase in the abundance of key transcriptional (TCF1, FOXO1 and Eomes) and metabolic (AMPK-α1, ATG7, ULK1, SIRT1, OPA1 and LAL) factors and an elevation in mitochondrial mass and reliance on fatty acid oxidation (FAO). Our data thus reveal for the first time that TGF-β regulates CD8+ T cell memory by triggering mTORC1Weak-mediated activation of the transcriptional FOXO1-TCF1-Eomes and metabolic AMPK-ULK1-ATG7 pathways. Given that induction of more qualified CD8+ TM cells is one of the ultimate goals of vaccination, our findings identify additional targets critical to TGF-β-induced T cell memory, which may greatly impact future vaccine development for the treatment of cancer and infectious diseases.