title: Functional requirements for inhibitory signal transmission by the immunomodulatory receptor CD300a.
abstract: BACKGROUND
  Activation signals can be negatively regulated by cell surface receptors bearing immunoreceptor tyrosine-based inhibitory motifs (ITIMs). CD300a, an ITIM bearing type I transmembrane protein, is expressed on many hematopoietic cells, including subsets of lymphocytes.
  
  
  RESULTS
  We have taken two approaches to further define the mechanism by which CD300a acts as an inhibitor of immune cell receptor signaling. First, we have expressed in Jurkat T cells a chimeric receptor consisting of the extracellular domains of killer-cell immunoglobulin-like receptor (KIR)2DL2 fused to the transmembrane and cytoplasmic segments of CD300a (KIR-CD300a) to explore surrogate ligand-stimulated inhibition of superantigen stimulated T cell receptor (TCR) mediated cell signaling. We found that intact CD300a ITIMs were essential for inhibition and that the tyrosine phosphorylation of these ITIMs required the src tyrosine kinase Lck. Tyrosine phosphorylation of the CD300a ITIMs created docking sites for both src homology 2 domain containing protein tyrosine phosphatase (SHP)-1 and SHP-2. Suppression of SHP-1 and SHP-2 expression in KIR-CD300a Jurkat T cells with siRNA and the use of DT40 chicken B cell lines expressing CD300a and deficient in several phosphatases revealed that SHP-1, but not SHP-2 or the src homology 2 domain containing inositol 5' phosphatase SHIP, was utilized by CD300a for its inhibitory activity.
  
  
  CONCLUSIONS
  These studies provide new insights into the function of CD300a in tuning T and B cell responses.
authors.affiliation: Laboratory of Molecular and Developmental Immunology, Division of Monoclonal Antibodies HFD-123, OBP/CDER/FDA, 29 Lincoln Drive; Bldg 29B, Room 3NN18, Bethesda, MD 20892, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: DeBell
authors.forename: Venkateswara R
authors.initials: VR
authors.lastname: Simhadri
authors.forename: John L
authors.initials: JL
authors.lastname: Mariano
authors.forename: Francisco
authors.initials: F
authors.lastname: Borrego
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism*; D001402:B-Lymphocytes / Q000378:metabolism*; D002460:Cell Line; D002645:Chickens; D006801:Humans; D000072181:Inositol Polyphosphate 5-Phosphatases; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000378:metabolism; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000378:metabolism; D011971:Receptors, Immunologic / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; C515070:CD300A protein, human; D011971:Receptors, Immunologic; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D010744:Phosphoric Monoester Hydrolases; C516724:PTPN11 protein, human; C509249:PTPN6 protein, human; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D000072181:Inositol Polyphosphate 5-Phosphatases