Ubiquitin specific protease 1 expression and function in T cell immunity
T cells are essential mediators of the immune responses against infectious diseases and provide long-lived protection from reinfection. The differentiation of naive T cells to effector T cells and subsequent differentiation and persistence of memory T cell populations in response to infection is a highly regulated process. E protein transcription factors and their inhibitors, Id proteins, are important regulators of both CD4+ and CD8+ T cell responses; however, their regulation at the protein level has not been explored. Recently, the deubiquitinase USP1 was shown to stabilize Id2 and modulate cellular differentiation in osteosarcomas. Here, we investigated a role for Usp1 in posttranslational control of Id2 and Id3 in T cells. We show that Usp1 was upregulated in T cells following activation in vitro or following infection in vivo, and the extent of Usp1 expression correlated with the degree of T cell expansion. Usp1 directly interacted with Id2 and Id3 following T cell activation. However, Usp1-deficiency did not impact Id protein abundance in effector T cells or alter effector CD8+ T cell expansion or differentiation following a primary infection. Usp1 deficiency did result in a gradual loss of memory cells over time and impaired accumulation and altered differentiation following a secondary infection. Together, these results identify Usp1 as a player in modulating recall responses at the protein level and highlight differences in regulation of T cell responses between primary and subsequent infection encounters. Finally, our observations reveal that differential regulation of Id2/3 proteins between immune vs non-immune cell types.