Functions as an activating and costimulatory receptor involved in immunosurveillance upon binding to various cellular stress-inducible ligands displayed at the surface of autologous tumor cells and virus-infected cells. Provides both stimulatory and costimulatory innate immune responses on activated killer (NK) cells, leading to cytotoxic activity. Acts as a costimulatory receptor for T-cell receptor (TCR) in CD8(+) T-cell-mediated adaptive immune responses by amplifying T-cell activation. Stimulates perforin-mediated elimination of ligand-expressing tumor cells. Signaling involves calcium influx, culminating in the expression of TNF-alpha. Participates in NK cell-mediated bone marrow graft rejection. May play a regulatory role in differentiation and survival of NK cells. Binds to ligands belonging to various subfamilies of MHC class I-related glycoproteins (By similarity). Homodimer; disulfide-linked. Heterohexamer composed of two subunits of KLRK1 and four subunits of HCST/DAP10. Interacts (via transmembrane domain) with HCST/DAP10 (via transmembrane domain); the interaction is required for KLRK1 NK cell surface and induces NK cell-mediated cytotoxicity. Can form disulfide-bonded heterodimer with CD94 (By similarity). Interacts with CEACAM1; recruits PTPN6 that dephosphorylates VAV1 (By similarity). Colocalized with HCST on the cell surface. Natural killer cells. Is not capable of signal transduction by itself, but operates through the adapter protein HCST.