title: Interaction of C-type lectin-like receptors NKp65 and KACL facilitates dedicated immune recognition of human keratinocytes.
abstract: Many well-known immune-related C-type lectin-like receptors (CTLRs) such as NKG2D, CD69, and the Ly49 receptors are encoded in the natural killer gene complex (NKC). Recently, we characterized the orphan NKC gene CLEC2A encoding for KACL, a further member of the human CLEC2 family of CTLRs. In contrast to the other CLEC2 family members AICL, CD69, and LLT1, KACL expression is mostly restricted to skin. Here we show that KACL is a non-disulfide-linked homodimeric surface receptor and stimulates cytotoxicity by human NK92MI cells. We identified the corresponding activating receptor on NK92MI cells that is encoded adjacently to the CLEC2A locus and binds KACL with high affinity. This CTLR, termed NKp65, stimulates NK cytotoxicity and release of proinflammatory cytokines upon engagement of cell-bound KACL. NKp65, a distant relative of the human activating NK receptor NKp80, possesses an amino-terminal hemITAM that is required for NKp65-mediated cytotoxicity. Finally, we show that KACL expression is mainly restricted to keratinocytes. Freshly isolated keratinocytes express KACL and are capable of stimulating NKp65-expressing cells in a KACL-dependent manner. Thus, we report a unique NKC-encoded receptor-ligand system that may fulfill a dedicated function in the immunobiology of human skin.
authors.affiliation: Department of Immunology, Institute for Cell Biology, Eberhard-Karls-University Tübingen, 72076 Tübingen, Germany.
authors.forename: Jessica
authors.initials: J
authors.lastname: Spreu
authors.forename: Sabrina
authors.initials: S
authors.lastname: Kuttruff
authors.forename: Veronika
authors.initials: V
authors.lastname: Stejfova
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Dennehy
authors.forename: Birgit
authors.initials: B
authors.lastname: Schittek
authors.forename: Alexander
authors.initials: A
authors.lastname: Steinle
mesh_terms: D000595:Amino Acid Sequence; D015550:Cell Degranulation; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D003602:Cytotoxicity, Immunologic; D004220:Disulfides / Q000378:metabolism; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000276:immunology* / Q000502:physiology; D007694:Killer Cells, Natural / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D037181:Lectins, C-Type / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D055503:Protein Multimerization; D055630:Receptors, NK Cell Lectin-Like / Q000737:chemistry / Q000378:metabolism*; D055607:Receptors, Natural Killer Cell / Q000378:metabolism
chemical_list: C526358:CLEC2A protein, human; D016207:Cytokines; D004220:Disulfides; C431711:KLRF1 protein, human; C548774:KLRF2 protein, human; D037181:Lectins, C-Type; D055630:Receptors, NK Cell Lectin-Like; D055607:Receptors, Natural Killer Cell