Transmembrane adapter protein which associates with KLRK1 to form an activation receptor KLRK1-HCST in lymphoid and myeloid cells; this receptor plays a major role in triggering cytotoxicity against target cells expressing cell surface ligands such as MHC class I chain-related MICA and MICB, and UL16-binding proteins (ULBPs); these ligands are up-regulated by stress conditions and pathological state such as viral infection and tumor transformation. Functions as docking site for PI3-kinase PIK3R1 and GRB2. Interaction of ULBPs with KLRK1-HCST triggers calcium mobilization and activation of the PIK3R1, MAP2K/ERK, and JAK2/STAT5 signaling pathways. Both PIK3R1 and GRB2 are required for full KLRK1-HCST-mediated activation and ultimate killing of target cells. In NK cells, KLRK1-HCST signaling directly induces cytotoxicity and enhances cytokine production initiated via DAP12/TYROBP-associated receptors. In T-cells, it provides primarily costimulation for TCR-induced signals. KLRK1-HCST receptor plays a role in immune surveillance against tumors and is required for cytolysis of tumors cells; indeed, melanoma cells that do not express KLRK1 ligands escape from immune surveillance mediated by NK cells (By similarity). Homodimer; Disulfide-linked. Heterohexamer composed of four subunits of HCST/DAP10 and two subunits of KLRK1. Interacts (via transmembrane domain) with KLRK1 (via transmembrane domain); the interaction is required for KLRK1 NK cell surface and induces NK cell-mediated cytotoxicity. Interacts with PIK3R1 and GRB2. Interacts with CLEC5A. Forms an CLEC5A/TYROBP/HCST trimolecular complex depending almost solely on TYROBP (By similarity). Interacts with KLRK1. Interacts with CD300H (By similarity). Expressed predominantly in lymphohematopoietic tissues. Phosphorylated; PIK3R1 and GRB2 associate specifically with tyrosine-phosphorylated HCST. O-glycosylated. Belongs to the DAP10 family.