The BASH/BLNK/SLP-65-associated protein BNAS1 regulates antigen-receptor signal transmission in B cells.
BASH/BLNK/SLP-65 is an adaptor protein necessary for the B cell receptor (BCR) signal transduction. Here we report the identification through the yeast two-hybrid system of a novel 26-kDa protein, BASH N-terminus-associated protein 1 (BNAS1), which interacts with the conserved and functionally important N-terminal domain of BASH/BLNK/SLP-65. BNAS1 presumably contains four transmembrane domains and the leucine zipper (LZ) motif, and is expressed ubiquitously. The association of BNAS1 with BASH/BLNK/SLP-65 through its LZ motif in vertebrate cells was demonstrated by immunoprecipitation assay. Confocal microscopy revealed that exogenously expressed BNAS1 is localized to the endoplasmic reticulum (ER) and the nuclear envelope. BASH/BLNK/SLP-65 alone was present diffusely in the cytoplasm, but localized to the same position as BNAS1 when co-expressed with BNAS1. Their co-localization was dependent on the domains containing the LZ motif of both molecules. BCR-signaled transcriptional activation of Elk-1 was suppressed by over-expression of BNAS1 in DT40 chicken B cells, and conversely augmented in the BNAS1-deficient DT40 cells, which was restored by BNAS1 reconstitution. This augmentation of Elk-1 activation in the BNAS1-deficient cells was abolished selectively by Jun N-terminal kinase (JNK) inhibitor, suggesting that BNAS1 regulates Elk-1 activation through JNK. Taken together, these results suggest that BNAS1 interacts with BASH/BLNK/SLP-65 at the ER and/or the outer nuclear membrane and is involved in the regulation of the signal transmission via mitogen-activated protein kinases leading to Elk-1 activation.
Katahira
Takashi
T
Division of Molecular Biology, Research Institute for Biological Sciences, Tokyo University of Science, 2669 Yamazaki, Noda, Chiba 278-0022, Japan.
Imamura
Yasuhiro
Y
Kitamura
Daisuke
D
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D015153:Blotting, Western; D002352:Carrier Proteins / Q000276:immunology*; D002467:Cell Nucleus / Q000378:metabolism; D002645:Chickens; D004721:Endoplasmic Reticulum / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000276:immunology; D018390:Gene Targeting; D006801:Humans; D008213:Lymphocyte Activation / Q000276:immunology*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D051379:Mice; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010750:Phosphoproteins / Q000276:immunology*; D021381:Protein Transport / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000276:immunology*; D020798:Two-Hybrid System Techniques; D050807:ets-Domain Protein Elk-1 / Q000276:immunology
D048868:Adaptor Proteins, Signal Transducing; C113939:B cell linker protein; D002352:Carrier Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D050807:ets-Domain Protein Elk-1; D048049:Extracellular Signal-Regulated MAP Kinases