Mitochondrial metabolism is known to be important for T-cell activation. However, its involvement in effector T-cell differentiation has just begun to gain attention. Importantly, how metabolic pathways are integrated with T-cell activation and effector cell differentiation and function remains largely unknown.

We sought to test our hypothesis that RhoA GTPase orchestrates glycolysis for T_H2 cell differentiation and T_H2-mediated allergic airway inflammation.

Conditional RhoA-deficient mice were generated by crossing RhoA^flox/flox mice with CD2-Cre transgenic mice. Effects of RhoA on T_H2 differentiation were evaluated based on in vitro T_H2-polarized culture conditions and in vivo in ovalbumin-induced allergic airway inflammation. Cytokine levels were measured by using intracellular staining and ELISA. T-cell metabolism was measured by using the Seahorse XF24 Analyzer and flow cytometry.

Disruption of RhoA inhibited T-cell activation and T_H2 differentiation in vitro and prevented the development of allergic airway inflammation in vivo, with no effect on T_H1 cells. RhoA deficiency in activated T cells led to multiple defects in metabolic pathways, such as glycolysis and oxidative phosphorylation. Importantly, RhoA couples glycolysis to T_H2 cell differentiation and allergic airway inflammation through regulating IL-4 receptor mRNA expression and T_H2-specific signaling events. Finally, inhibition of Rho-associated protein kinase, an immediate downstream effector of RhoA, blocked T_H2 differentiation and allergic airway inflammation.

RhoA is a key component of the signaling cascades leading to T_H2 differentiation and allergic airway inflammation at least in part through control of T-cell metabolism and the Rho-associated protein kinase pathway.