ERK activation in CAR T cells is amplified by CD28-mediated increase in CD3ζ phosphorylation
Chimeric antigen receptors (CARs) are engineered receptors that mediate T cell activation. CARs are comprised of activating and costimulatory intracellular signaling domains derived from endogenous T cells that initiate signaling required for T cell activation, including ERK activation through the MAPK pathway. Understanding the mechanisms by which co-stimulatory domains influence signaling can help guide the design of next-generation CARs. Therefore, we constructed an experimentally-validated computational model of anti-CD19 CARs in T cells bearing the CD3{zeta} domain alone or in combination with CD28. We used ensemble modeling to explore different mechanisms of CD28 co-stimulation on the ERK response time. Model simulations show that CD28 primarily influences ERK activation by enhancing the phosphorylation kinetics of CD3{zeta}, predictions that are validated by experimental measurements. Overall, we present a mechanistic mathematical modeling framework that can be used to gain insights into the mechanism of CAR T cell activation and produce new testable hypotheses.