title: Role of tyrosine phosphorylation of HS1 in B cell antigen receptor-mediated apoptosis.
abstract: The 75-kD HS1 protein is highly tyrosine-phosphorylated during B cell antigen receptor (BCR)-mediated signaling. Owing to low expression of HS1, WEHI-231-derived M1 cells, unlike the parental cells, are insensitive to BCR-mediated apoptosis. Here, we show that BCR-associated tyrosine kinases Lyn and Syk synergistically phosphorylate HS1, and that Tyr-378 and Tyr-397 of HS1 are the critical residues for its BCR-induced phosphorylation. In addition, unlike wild-type HS1, a mutant HS1 carrying the mutations Phe-378 and Phe-397 was unable to render M1 cells sensitive to apoptosis. Wild-type HS1, but not the mutant, localized to the nucleus under the synergy of Lyn and Syk. Thus, tyrosine phosphorylation of HS1 is required for BCR-induced apoptosis and nuclear translocation of HS1 may be a prerequisite for B cell apoptosis.
authors.affiliation: Department of Oncology, Institute of Medical Science, University of Tokyo, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamanashi
authors.forename: T
authors.initials: T
authors.lastname: Fukuda
authors.forename: H
authors.initials: H
authors.lastname: Nishizumi
authors.forename: T
authors.initials: T
authors.lastname: Inazu
authors.forename: K
authors.initials: K
authors.lastname: Higashi
authors.forename: D
authors.initials: D
authors.lastname: Kitamura
authors.forename: T
authors.initials: T
authors.lastname: Ishida
authors.forename: H
authors.initials: H
authors.lastname: Yamamura
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001402:B-Lymphocytes / Q000378:metabolism*; D001798:Blood Proteins / Q000378:metabolism*; D019556:COS Cells; D004792:Enzyme Precursors / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D015398:Signal Transduction; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001798:Blood Proteins; D004792:Enzyme Precursors; C061909:HCLS1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D011947:Receptors, Antigen, B-Cell; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; C000606897:Syk protein, mouse; D019061:src-Family Kinases