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. Is not capable of signal transduction by itself, but operates through the adapter protein HCST.