title: Identification and characterization of a novel BASH N terminus-associated protein, BNAS2.
abstract: A B cell-specific adaptor protein, BASH (also known as BLNK or SLP-65), is crucial for B cell receptor (BCR) signaling. BASH binds to various signaling intermediates, such as Btk, PLCgamma2, Vav, and Grb2, through its well defined motifs. Although functional significance of such interactions has been documented, BASH-mediated signal transduction mechanism is not fully understood. Using the yeast two-hybrid system, we have identified a novel protein that binds to a conserved N-terminal domain of BASH, which we named BNAS2 (BASH N terminus associated protein 2). From its deduced amino acid sequence, BNAS2 is presumed to contain four transmembrane domains, which are included in a central MARVEL domain, and to localize to endoplasmic reticulum. BNAS2 was co-precipitated with BASH as well as Btk and ERK2 from a lysate of mouse B cell line. In the transfected cells, the exogenous BNAS2 was localized in a mesh-like structure in the cytoplasm resembling that of endoplasmic reticulum (ER) and nuclear membrane. BASH was co-localized with BNAS2 in a manner dependent on its N-terminal domain. RT-PCR analysis indicated that BNAS2 mRNA is expressed ubiquitously except for plasma cells. In chicken B cell line DT40, overexpression of BNAS2 resulted in an enhancement of BCR ligation-mediated transcriptional activation of Elk1, but not of NF-kappaB, in a manner dependent on the dose of BNAS2. Thus BNAS2 may serve as a scaffold for signaling proteins such as BASH, Btk, and ERK at the ER and nuclear membrane and may facilitate ERK activation by signaling from cell-surface receptors.
authors.affiliation: Research Institute for Biological Sciences, Tokyo University of Science, 2669 Yamazaki, Noda-city, Chiba 278-0022, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Imamura
authors.forename: Takashi
authors.initials: T
authors.lastname: Katahira
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kitamura
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000077329:Agammaglobulinaemia Tyrosine Kinase; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism; D015153:Blotting, Western; D019556:COS Cells; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D002645:Chickens; D004268:DNA-Binding Proteins; D004721:Endoplasmic Reticulum / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000502:physiology*; D051379:Mice; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D008969:Molecular Sequence Data; D016328:NF-kappa B / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014157:Transcription Factors; D015533:Transcriptional Activation; D014162:Transfection; D020798:Two-Hybrid System Techniques; D050807:ets-Domain Protein Elk-1
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C113939:B cell linker protein; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C494113:Elk1 protein, mouse; D008565:Membrane Proteins; D016328:NF-kappa B; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; D000077329:Agammaglobulinaemia Tyrosine Kinase; D019950:Mitogen-Activated Protein Kinase 1