DOK2 (docking protein 2) functions as an enzymatically inactive scaffolding protein that serves as a tumor suppressor and negative regulator of cellular signaling pathways 1. The protein acts through direct binding to phosphorylated receptor motifs, as demonstrated in CD200 receptor signaling where DOK2 binds the phosphorylated NPLY motif and subsequently recruits RasGAP to inhibit myeloid cell activation 2. DOK2 regulates multiple signaling cascades including Ras/MAPK/ERK and PI3K/AKT/mTOR pathways 1. In immune regulation, DOK2 provides negative feedback control in natural killer cells, with overexpression reducing NK cell activation and gene ablation leading to increased IFN-γ production 3. Disease relevance is significant, as DOK2 functions as a tumor suppressor with compound haploinsufficiency of DOK2 and DUSP4 promoting lung tumorigenesis through synergistic MAPK activation 4. Clinically, reduced DOK2 expression occurs early in HTLV-I-induced leukemogenesis 5, and the protein has been identified as a potential blood biomarker for schizophrenia 6 and as an autoantigen target in autoimmune hepatitis, where anti-DOK2 antibodies correlate with disease activity 7.