Chimeric antigen receptor (CAR) signaling machinery (CAR signaling machinery)

The Chimeric Antigen Receptor (CAR) signaling machinery is the synthetic intracellular component of CAR-T cells that mediates T-cell activation, proliferation, and cytotoxicity upon binding to a target antigen. This machinery typically integrates the CD3-zeta chain (providing Signal 1) with costimulatory domains such as CD28 or 4-1BB (providing Signal 2), effectively mimicking the natural T-cell receptor (TCR) complex but in an MHC-independent manner [1, 3, 5]. Upon antigen engagement, these domains are phosphorylated by kinases like Lck, initiating a robust signaling cascade through ZAP-70 and downstream pathways such as PI3K/Akt and NF-kappaB [1, 2]. While this machinery is the cornerstone of the high response rates seen in hematologic malignancies, its potency is also the primary driver of significant toxicities, including cytokine release syndrome (CRS) and neurotoxicity [4, 5]. Consequently, the signaling machinery is increasingly viewed as a tunable therapeutic target itself; for example, the tyrosine kinase inhibitor dasatinib can be used as a "pharmacologic off-switch" to rapidly and reversibly inhibit CAR-T cell activity by blocking the phosphorylation of these intracellular domains [2]. Current engineering efforts focus on refining this machinery through the use of alternative costimulatory domains, logic gates, and inducible systems to enhance safety and efficacy, particularly in the context of solid tumors [1, 3].

Other names

CAR intracellular signaling domainCAR endodomainCAR signaling complexChimeric antigen receptor signaling tailCAR-T signaling machinery

The machinery functions by aggregating intracellular signaling domains (typically CD3-zeta and CD28 or 4-1BB) upon antigen binding, leading to phosphorylation by Lck and recruitment of ZAP-70, which triggers downstream T-cell activation pathways independent of MHC [1, 2, 3].