Synergistic and additive interactions between receptor signaling networks drive the regulatory T cell versus T helper 17 cell fate choice

Douglas S Prado,Richard T Cattley,Corey W Shipman,Cassandra Happe,Mijoon Lee,William C Boggess,Matthew L Macdonald,William F Hawse

doi:10.1016/j.jbc.2021.101330

Douglas S Prado, Richard T Cattley + Show 6 more

Open Access

https://doi.org/10.1016/j.jbc.2021.101330

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Abstract

CD4+ T cells differentiate into subsets that promote immunity or minimize damage to the host. T helper 17 cells (Th17) are effector cells that function in inflammatory responses. T regulatory cells (Tregs) maintain tolerance and prevent autoimmunity by secreting immunosuppressive cytokines and expressing check point receptors. While the functions of Th17 and Treg cells are different, both cell fate trajectories require T cell receptor (TCR) and TGF-β receptor (TGF-βR) signals, and Th17 polarization requires an additional IL-6 receptor (IL-6R) signal. Utilizing high-resolution phosphoproteomics, we identified that both synergistic and additive interactions between TCR, TGF-βR, and IL-6R shape kinase signaling networks to differentially regulate key pathways during the early phase of Treg versus Th17 induction. Quantitative biochemical analysis revealed that CD4+ T cells integrate receptor signals via SMAD3, which is a mediator of TGF-βR signaling. Treg induction potentiates the formation of the canonical SMAD3/4 trimer to activate a negative feedback loop through kinases PKA and CSK to suppress TCR signaling, phosphatidylinositol metabolism, and mTOR signaling. IL-6R signaling activates STAT3 to bind SMAD3 and block formation of the SMAD3/4 trimer during the early phase of Th17 induction, which leads to elevated TCR and PI3K signaling. These data provide a biochemical mechanism by which CD4+ T cells integrate TCR, TGF-β, and IL-6 signals via generation of alternate SMAD3 complexes that control the development of early signaling networks to potentiate the choice of Treg versus Th17 cell fate.

Highlights

T cells continuously circulate throughout the body, encounter many different environments, and employ multiple transmembrane receptors to sense changes in their local microenvironment
T regulatory cells (Tregs) induction requires signals from T cell receptor (TCR)/CD28 and TGF-β receptors, and T helper cell 17 (Th17) requires an additional signal from the IL-6 receptor
This work revealed that CD4+ T cells integrate T cell, TGF- and IL-6 receptor signals by generating different SMAD3 complexes (Fig 5)

Summary

Introduction

T cells continuously circulate throughout the body, encounter many different environments, and employ multiple transmembrane receptors to sense changes in their local microenvironment. We profiled the phosphoproteomes that evolve in CD4+ T cells stimulated during early Treg or Th17 polarization This analysis revealed that phosphorylation regulated multiple proteins involved with signaling and metabolism. These alterations culminated in suppressed flux through the conical TCR signaling and mTOR pathways during Treg induction. During Treg induction, signaling through the TCR and TGF-β receptors promote formation of the SMAD3/4 complex, which in turn initiates a negative feedback loop via PKA to suppress TCR, PI3K and mTORC signals. During Th17 induction, signaling through the TCR, IL-6 receptor and Journal Pre-proof TGF-β receptor promotes the formation of a STAT3-SMAD3 complex, which does not bind nor activate. This work provides a molecular basis for how signals from the TCR, TGF-βR and IL-6R synergize to select the Treg versus Th17 cell fate choice

Results

Discussion

Experimental Procedures