Natural killer cell p44-related ligand (NKp44L) (NKp44L)

Natural killer cell p44-related ligand (NKp44L) refers to a group of molecules expressed on the surface of stressed, infected, or transformed cells that serve as ligands for the natural cytotoxicity receptor NKp44 (NCR2). The most prominent activating ligand is a specific splice variant of the Mixed-lineage leukemia protein 5 (MLL5/KMT2E), which is typically a nuclear protein but is expressed on the cell surface in various cancers and HIV-infected cells (1.1.1, 2.1.1). Other identified ligands include Proliferating Cell Nuclear Antigen (PCNA), which acts as an inhibitory ligand by recruiting NKp44 to the immunological synapse, and Platelet-Derived Growth Factor D (PDGF-DD) (1.2.2, 1.2.4). These ligands play a critical role in the innate immune system's ability to recognize and eliminate tumor cells and virally infected cells through non-MHC restricted mechanisms (1.2.1, 2.1.5). Therapeutic strategies targeting these ligands include the development of NKp44-based chimeric antigen receptor (CAR) T cells and monoclonal antibodies designed to either enhance NK cell-mediated killing or block inhibitory signals used by tumors to escape immunosurveillance (1.1.1, 2.1.2).

Other names

Natural cytotoxicity receptor 2 ligandNKp44 ligandMLL5 isoform NKp44LKMT2E isoform NKp44LNCR2 ligand

Binding to the NKp44 (NCR2) receptor on activated natural killer (NK) cells to trigger cytotoxicity and cytokine production (e.g., IFN-gamma) or, in the case of inhibitory ligands like PCNA, to suppress NK cell activity via ITIM signaling.