The TCR-SUB1-DOCK2 axis promotes autoimmunity by driving pathogenic CD4⁺ T cell tissue infiltration

Aberrant tissue infiltration by activated CD4⁺ T cells is a central driver of autoimmunity, yet the molecular checkpoints governing antigen-specific T cell ingress remain poorly defined. We found that the transcription factor SUB1 was selectively upregulated in CD4⁺ T cells from individuals with autoimmune diseases. SUB1 expression was induced by the T cell receptor (TCR)-interferon regulatory factor 4 (IRF4) transcription factor axis. Conditional deletion of Sub1 in T cells reduced the expression of migration regulator dedicator of cytokinesis 2 (DOCK2), inhibited Rac-dependent actin polymerization and T cell motility, and prevented the onset of experimental autoimmune encephalomyelitis. Mechanistically, SUB1 underwent liquid-liquid phase separation to form biomolecular condensates that opened chromatin at the Junb and Dock2 loci. It then directly trans-activated Junb transcription and partnered with JUNB to amplify Dock2 transcription. Therefore, SUB1 is a critical gatekeeper of pathogenic T cell trafficking, and by linking TCR signaling to cytoskeletal remodeling, the TCR-SUB1-DOCK2 axis emerges as a tractable, migration-focused therapeutic target in autoimmune disorders.