CD28-CBCA driven PKM splicing licenses CD8 T cell glycolysis and effector function

T cells stimulated in the absence of CD28 costimulation are functionally anergic, characterized by reduced glucose metabolism and ability to produce effector cytokines. Surprisingly, previous studies have shown relatively few CD28-specific changes in gene transcription upon costimulation. Using mice expressing mutations in the CD28 cytoplasmic tail, we show a major effect of CD28 costimulation is alternative splicing of numerous genes including the glycolytic enzyme pyruvate kinase (Pkm), which is preferentially spliced from Pkm1 to Pkm2 upon stimulation. PKM2 is dispensable for T cell activation, but necessary for CD8+ T cells to utilize aerobic glycolysis, produce effector cytokines, and provide anti-tumor immunity. Mechanistically, CD28 regulates expression of the Cap-Binding Complex adaptor protein ARS2, which binds Pkm splicing factors and facilitates their interaction with the elongating transcript. Data suggest a major function of CD28 costimulation is control of RNA biogenesis in support of T cell transcriptome remodeling and acquisition of effector function. Overall design: RNA was sequenced from murine T cells from mice of the indicated genotype was performed at 24, or 72 hours post stimulation. Total of 34 samples. Biological replicates at each time point : WT (2), ARS2 KO (3), CD28 KO (2), CD28 DKI (3), CD28 AYAA (3), CD28 Y170F (3), all samples were compared relative to unstimulated WT T cells (n=2)