T-cell surface glycoprotein CD3 zeta chain and Zeta-chain-associated protein kinase 70 complex (CD3ζ-ZAP70 complex)

The CD3ζ-ZAP70 signaling axis is a fundamental component of the T-cell receptor (TCR) complex, responsible for converting extracellular antigen recognition into intracellular activation signals [1, 2]. Upon TCR engagement, the immunoreceptor tyrosine-based activation motifs (ITAMs) within the CD3ζ (CD247) cytoplasmic tail are phosphorylated by the Src-family kinase Lck, creating high-affinity docking sites for the tandem SH2 domains of the Zeta-chain-associated protein kinase 70 (ZAP70) [3, 4]. Once recruited and activated, ZAP70 phosphorylates downstream adapter proteins such as the Linker for Activation of T cells (LAT) and SLP-76, which serve as scaffolds for the assembly of a larger signalosome that initiates calcium flux, Ras-MAPK signaling, and NF-κB activation [3]. This complex is a critical therapeutic target; its overactivity is linked to autoimmune disorders and lymphoid malignancies, while its deficiency or dysfunction leads to severe combined immunodeficiency (SCID) [2, 4]. Modern immunotherapy leverages this pathway by incorporating the CD3ζ signaling domain into Chimeric Antigen Receptors (CARs) to drive potent anti-tumor responses in hematologic cancers [5]. Pharmacological modulation includes small-molecule inhibitors of ZAP70 or upstream kinases like Lck to manage inflammatory conditions, prevent transplant rejection, or treat specific leukemias [6, 7]. Additionally, ZAP-70 expression levels serve as a significant prognostic biomarker in chronic lymphocytic leukemia (CLL), correlating with disease progression and patient survival [8].

Other names

CD247ZAP-70T-cell receptor zeta chainCD3ZSRKSTDTZPLinker for activation of T-cells (LAT)SLP-76 (LCP2)

The mechanism involves the phosphorylation of ITAMs on the CD3ζ chain by Lck, which recruits ZAP70 via its SH2 domains. ZAP70 is then activated by Lck-mediated phosphorylation and subsequently phosphorylates downstream adapters like LAT and SLP-76 to propagate the TCR signal [3, 4].