UCP3 reciprocally controls CD4+ Th17 and Treg cell differentiation

Area of Science:

• Immunology
• Mitochondrial Biology
• Cellular Metabolism

Background:

• Uncoupling proteins (UCPs) are mitochondrial proteins involved in proton transport.
• UCP3 expression has been noted in various immune cells, including thymocytes and lymphocytes.
• The precise role of UCP3 in T cell activation and differentiation remains largely unexplored.

Purpose of the Study:

• To investigate the role of UCP3 in naive CD4+ T cell activation and differentiation.
• To determine the impact of UCP3 deficiency on T cell proliferation, cytokine production, and lineage commitment.
• To explore the potential of UCP3 as a therapeutic target in T cell-mediated autoimmune conditions.

Main Methods:

• Analysis of Ucp3 mRNA expression in naive and activated CD4+ T cells.
• Comparative assessment of proliferation, cytokine production (IL-2, IL-17A), and surface marker expression (CD25, CD69, FoxP3) in Ucp3-/- and Ucp3+/+ T cells.
• In vitro differentiation assays for Th17 and induced regulatory T (iTreg) cells.
• In vivo studies using antigen-specific T cells from immunized mice.
• IL-2 neutralization experiments.

Main Results:

• Ucp3 is expressed in naive CD4+ T cells and downregulated upon activation.
• Ucp3-/- T cells exhibit enhanced proliferation, increased IL-2 production, and elevated CD25/CD69 expression compared to Ucp3+/+ T cells.
• Ucp3 deficiency promotes FoxP3 expression under iTreg conditions but reduces IL-17A production under Th17 conditions.
• Altered T cell responses in Ucp3-/- mice were partially reversed by IL-2 neutralization.
• Ucp3 ablation impacts the Th17:Treg cell balance both in vitro and in vivo.

Conclusions:

• UCP3 functions as a rheostat, dampening TCR and CD28 co-receptor signaling to limit early T cell activation.
• UCP3 deficiency leads to heightened T cell activation and influences the balance between Th17 and iTreg cells.
• UCP3 represents a potential therapeutic target for managing Th17 cell-mediated autoimmune diseases.