title: CD229 (Ly9) lymphocyte cell surface receptor interacts homophilically through its N-terminal domain and relocalizes to the immunological synapse.
abstract: CD229 is a member of the CD150 family of the Ig superfamily expressed on T and B cells. Receptors of this family regulate cytokine production and cytotoxicity of lymphocytes and NK cells. The cytoplasmic tail of CD229 binds to SAP, a protein that is defective in X-linked lymphoproliferative syndrome. To identify the CD229 ligand, we generated a soluble Ig fusion protein containing the two N-terminal extracellular domains of human CD229 (CD229-Ig). CD229-Ig bound to CD229-transfected cells, whereas no binding was detected on cells expressing other CD150 family receptors, showing that CD229 binds homophilically. Both human and mouse CD229 interacted with itself. Domain deletion mutants showed that the N-terminal Ig-domain mediates homophilic adhesion. CD229-CD229 binding was severely compromised when the charged amino acids E27 and E29 on the predicted B-C loop and R89 on the F-G loop of the N-terminal domain were mutated to alanine. In contrast, one mutation, R44A, enhanced the homophilic interaction. Confocal microscopy image analysis revealed relocalization of CD229 to the contact area of T and B cells during Ag-dependent immune synapse formation. Thus, CD229 is its own ligand and participates in the immunological synapse.
authors.affiliation: Immunology Unit, Department of Cellular Biology and Pathology, Medical School, University of Barcelona, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Romero
authors.forename: Nuria
authors.initials: N
authors.lastname: Zapater
authors.forename: María
authors.initials: M
authors.lastname: Calvo
authors.forename: Susana G
authors.initials: SG
authors.lastname: Kalko
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: de la Fuente
authors.forename: Victoria
authors.initials: V
authors.lastname: Tovar
authors.forename: Charlotte
authors.initials: C
authors.lastname: Ockeloen
authors.forename: Pilar
authors.initials: P
authors.lastname: Pizcueta
authors.forename: Pablo
authors.initials: P
authors.lastname: Engel
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D017951:Antigen Presentation / Q000235:genetics / Q000276:immunology; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism; D015703:Antigens, CD / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D019556:COS Cells; D002450:Cell Communication / Q000235:genetics / Q000276:immunology*; D045744:Cell Line, Tumor; D006801:Humans; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000235:genetics; D051379:Mice; D016297:Mutagenesis, Site-Directed; D010449:Peptide Mapping; D011485:Protein Binding / Q000235:genetics / Q000276:immunology; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary / Q000235:genetics; D000071176:Signaling Lymphocytic Activation Molecule Family; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D014162:Transfection
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; C430423:LY9 protein, human; C498972:Ly9 protein, mouse; D000071176:Signaling Lymphocytic Activation Molecule Family