title: The LMP2A ITAM is essential for providing B cells with development and survival signals in vivo.
abstract: In Epstein-Barr virus-transformed B cells, known as lymphoblastoid cell lines (LCLs), LMP2A binds the tyrosine kinases Syk and Lyn, blocking B-cell receptor (BCR) signaling and viral lytic replication. SH2 domains in Syk mediate binding to a phosphorylated immunoreceptor tyrosine-based activation motif (ITAM) in LMP2A. Mutation of the LMP2A ITAM in LCLs eliminates Syk binding and allows for full BCR signaling, thereby delineating the significance of the LMP2A-Syk interaction. In transgenic mice, LMP2A causes a developmental alteration characterized by a block in surface immunoglobulin rearrangement resulting in BCR-negative B cells. Normally B cells lacking cognate BCR are rapidly apoptosed; however, LMP2A transgenic B cells develop and survive without a BCR. When bred into the recombinase activating gene 1 null (RAG(-/-)) background, all LMP2A transgenic lines produce BCR-negative B cells that develop and survive in the periphery. These data indicate that LMP2A imparts developmental and survival signals to B cells in vivo. In this study, LMP2A ITAM mutant transgenic mice were generated to investigate whether the LMP2A ITAM is essential for the survival phenotype in vivo. LMP2A ITAM mutant B cells develop normally, although transgene expression is comparable to that in previously described nonmutated LMP2A transgenic B cells. Additionally, LMP2A ITAM mutant mice are unable to promote B-cell development or survival when bred into the RAG(-/-) background or when grown in methylcellulose containing interleukin-7. These data demonstrate that the LMP2A ITAM is required for LMP2A-mediated developmental and survival signals in vivo.
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
authors.forename: M
authors.initials: M
authors.lastname: Merchant
authors.forename: R G
authors.initials: RG
authors.lastname: Caldwell
authors.forename: R
authors.initials: R
authors.lastname: Longnecker
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology* / Q000821:virology*; D001483:Base Sequence; D002472:Cell Transformation, Viral / Q000235:genetics / Q000276:immunology; D004854:Herpesvirus 4, Human; D008213:Lymphocyte Activation; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011971:Receptors, Immunologic / Q000235:genetics / Q000276:immunology*; D014763:Viral Matrix Proteins / Q000235:genetics / Q000276:immunology*
chemical_list: C037662:EBV-associated membrane antigen, Epstein-Barr virus; D011971:Receptors, Immunologic; D014763:Viral Matrix Proteins