title: LIR9, an immunoglobulin-superfamily-activating receptor, is expressed as a transmembrane and as a secreted molecule.
abstract: LIRs are immunoglobulinlike receptors that have activating and inhibitory functions in leukocytes. Here we report the identification of the first LIR family member, LIR9, expressed as a membrane-bound receptor and as a secreted molecule. We identified 4 different forms of LIR9, 2 of which encode transmembrane molecules and 2 encode secreted molecules. The transmembrane forms of LIR9 contain a short cytoplasmic domain and a charged arginine residue within the transmembrane region that is likely to mediate its association with another coreceptor. LIR9 is mostly expressed in myeloid cells, including monocytes and neutrophils. Cross-linking of LIR9 on the surfaces of monocytes induces calcium flux and secretion of the proinflammatory cytokines interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and IL-6, indicating that LIR9 could play a role in triggering innate immune responses.
authors.affiliation: Amgen Inc, Seattle, WA, USA. borgesl@amgen.com
authors.forename: Luis
authors.initials: L
authors.lastname: Borges
authors.forename: Marek
authors.initials: M
authors.lastname: Kubin
authors.forename: Tracy
authors.initials: T
authors.lastname: Kuhlman
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D001120:Arginine / Q000737:chemistry; D002118:Calcium / Q000378:metabolism; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents; D016207:Cytokines / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons; D006031:Glycosylation; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D007962:Leukocytes / Q000737:chemistry; D008565:Membrane Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009000:Monocytes / Q000737:chemistry; D009504:Neutrophils / Q000737:chemistry; D021382:Protein Sorting Signals / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D011971:Receptors, Immunologic / Q000737:chemistry / Q000235:genetics*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D003432:Cross-Linking Reagents; D016207:Cytokines; D018076:DNA, Complementary; D007375:Interleukin-1; D015850:Interleukin-6; C471973:LILRA5 protein, human; D008565:Membrane Proteins; D021382:Protein Sorting Signals; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D014409:Tumor Necrosis Factor-alpha; C413086:leukocyte-immunoglobulin--like receptor 6; D001120:Arginine; D002118:Calcium