RNF144A enforces IL-2-STAT5 dominance over RAF-ERK-MAPK signaling in antiviral CD8 T cells

Introduction/Rationale: IL-2 is central to CD8 T cell responses and signals via JAK-STAT5, RAF-ERK-MAPK, and PI3K-AKT pathways, but how STAT5-dominant output is enforced from this shared receptor is unclear. We hypothesized that uncharacterized IL-2-induced, STAT5-regulated E3 ubiquitin ligases sculpt this signaling hierarchy to optimize antiviral CD8 T cell function.

Methods: RNA-seq of human CD8 T cells stimulated with IL-2 ± JAK inhibition plus STAT5 ChIP-seq identified IL-2/STAT5-regulated ubiquitin genes. Rnf144a-/- mice and mixed bone marrow chimeras were used to define CD8-intrinsic roles during influenza infection. RNF144A localization and substrates were mapped by biochemical and imaging assays, and whole-blood transcriptomes from patients with moderate or severe influenza were analyzed to relate RNF144A expression and gene signatures to clinical severity.

Results: IL-2 broadly remodeled the T cell ubiquitin program, with RNF144A emerging as the most strongly induced STAT5-bound E3 ligase. RNF144A localized to the plasma membrane, associated with IL-2R and STAT5, and enhanced STAT5 recruitment and phosphorylation, sustaining STAT5-dependent transcription. In parallel, RNF144A acted as a bona fide E3 ligase that directly polyubiquitinated RAF1 for degradation, reducing ERK activation and thereby preserving JAK-STAT5 dominance over RAF-ERK-MAPK output. CD8 T cells from Rnf144a-/- mice showed impaired IL-2-induced effector gene expression, degranulation, and cytokine production, and CD8-intrinsic deficiency in mixed chimeras reduced antigen-specific responses and worsened weight loss and lung inflammation after influenza infection. In human influenza, RNF144A expression was reduced in severe disease, inversely correlated with an ERK-MAPK target gene signature, and discriminated severe from moderate cases with performance comparable to established severity markers.

Conclusion: RNF144A is an IL-2-STAT5-induced E3 ligase that enforces STAT5-dominant signaling and limits viral immunopathology.