Summary Nr4a receptors are activated by T cell receptor (TCR) signaling and play key roles in T cell differentiation. Which TCR signaling pathways regulate Nr4a receptors and their sensitivities to TCR signal strength and duration remains unclear. Using Nr4a1/Nur77-GFP and Nr4a3-Timer of cell kinetics and activity (Tocky) mice, we elucidate the signaling pathways governing Nr4a receptor expression. We reveal that Nr4a1–Nr4a3 are Src family kinase dependent. Moreover, Nr4a2 and Nr4a3 are attenuated by calcineurin inhibitors and bind nuclear factor of activated T cells 1 (NFAT1), highlighting a necessary and sufficient role for NFAT1 in the control of Nr4a2 and Nr4a3, but redundancy for Nr4a1. Nr4a1-GFP is activated by tonic and cognate signals during T cell development, whereas Nr4a3-Tocky requires cognate peptide:major histocompatibility complex (MHC) interactions for expression. Compared to Nr4a3-Tocky, Nr4a1-GFP is approximately 2- to 3-fold more sensitive to TCR signaling and is detectable by shorter periods of TCR signaling. These findings suggest that TCR signal duration may be an underappreciated aspect influencing the developmental fate of T cells in vivo.
Graphical Abstract
Highlights • Nr4a1 and Nr4a3 show differential dependency on the calcineurin/NFAT pathway • Nr4a1-GFP is expressed in developing Tcon and Treg within the thymus • Nr4a3-Timer expression is largely restricted to thymic and peripheral CD25+ Treg • Nr4a3-Timer requires a stronger and/or longer TCR signal for its expression
Nr4a reporter mice are useful tools for studying TCR signaling. Jennings et al. show that Nr4a3, but not Nr4a1, is NFAT pathway dependent, resulting in restricted Nr4a3-Timer expression during T cell development. Nr4a3-Timer requires stronger and/or longer TCR signals than Nr4a1-GFP, allowing an investigation of different TCR signaling grades in vivo.