title: Cloning and characterization of CD300d, a novel member of the human CD300 family of immune receptors.
abstract: Herein we present the cloning and molecular characterization of CD300d, a member of the human CD300 family of immune receptors. CD300d cDNA was cloned from RNA obtained from human peripheral blood mononuclear cells, and RT-PCR revealed the gene to be expressed in cells of myeloid lineage. The cloned cDNA encoded for a type I protein with a single extracellular Ig V-type domain and a predicted molecular mass of 21.5 kDa. The short cytoplasmic tail is lacking in any known signaling motif, but there is a negatively charged residue (glutamic acid) within the transmembrane domain. CD300d forms complexes with the CD300 family members, with the exception of CD300c. Contrary to other activating members of the CD300 family of receptors, surface expression of CD300d in COS-7-transfected cells required the presence of an immunoreceptor tyrosine-based activating motif-bearing adaptor (FcεRγ). Accordingly, we found that CD300d was able to recruit FcεRγ. Unexpectedly, we could not detect CD300d on the surface of cells expressing FcεRγ, suggesting the existence of unknown mechanisms regulating the trafficking of this molecule. The presence of other CD300 molecules also did not modify the intracellular expression of CD300d. In fact, the presence of CD300d decreased the levels of surface expression of CD300f but not CD300c. Our data suggest that the function of CD300d would be related to the regulation of the expression of other CD300 molecules and the composition of CD300 complexes on the cell surface.
authors.affiliation: Immunobiology Group, CIBBIM-Nanomedicine Program, Hospital Universitari Vall d'Hebrón, Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona 08035, Spain; Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine, Instituto de Salud Carlos III, Barcelona 08035, Spain.
authors.forename: Emma
authors.initials: E
authors.lastname: Comas-Casellas
authors.affiliation: Immunobiology Group, CIBBIM-Nanomedicine Program, Hospital Universitari Vall d'Hebrón, Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona 08035, Spain; Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine, Instituto de Salud Carlos III, Barcelona 08035, Spain,. Electronic address: agueda.martinez@vhir.org.
authors.forename: Águeda
authors.initials: Á
authors.lastname: Martínez-Barriocanal
authors.affiliation: Gene Translation Laboratory, Institute for Research in Biomedicine, Barcelona Science Park, Barcelona 08028, Spain, and.
authors.forename: Francesc
authors.initials: F
authors.lastname: Miró
authors.affiliation: Immunobiology Group, CIBBIM-Nanomedicine Program, Hospital Universitari Vall d'Hebrón, Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona 08035, Spain; Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine, Instituto de Salud Carlos III, Barcelona 08035, Spain.
authors.forename: Aroa
authors.initials: A
authors.lastname: Ejarque-Ortiz
authors.affiliation: Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine, Instituto de Salud Carlos III, Barcelona 08035, Spain,; Drug Delivery and Targeting Group, CIBBIM-Nanomedicine Program, Hospital Universitari Vall d'Hebrón, Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona 08035, Spain.
authors.forename: Simo
authors.initials: S
authors.lastname: Schwartz
authors.affiliation: Biochemistry Unit, Faculty of Medicine, Institut d'Investigacions Biomèdiques August Pi i Sunyer, University of Barcelona, Barcelona 08036, Spain.
authors.forename: Margarita
authors.initials: M
authors.lastname: Martín
authors.affiliation: Immunobiology Group, CIBBIM-Nanomedicine Program, Hospital Universitari Vall d'Hebrón, Institut de Recerca, Universitat Autònoma de Barcelona, Barcelona 08035, Spain; Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine, Instituto de Salud Carlos III, Barcelona 08035, Spain,. Electronic address: joan.sayos@vhir.org.
authors.forename: Joan
authors.initials: J
authors.lastname: Sayós
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005786:Gene Expression Regulation / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism*; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D017455:Receptors, IgE / Q000235:genetics / Q000378:metabolism; D011971:Receptors, Immunologic / Q000096:biosynthesis* / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: C572120:CD300LD protein, human; D018076:DNA, Complementary; C543372:FcepsilonRI gamma-chain, human; D046912:Multiprotein Complexes; D017455:Receptors, IgE; D011971:Receptors, Immunologic