title: The B lymphocyte adaptor molecule of 32 kD (Bam32) regulates B cell antigen receptor signaling and cell survival.
abstract: The B lymphocyte-associated adaptor protein 32 kD in size (Bam32) is expressed at high levels in germinal center (GC) B cells. It has an NH(2)-terminal src homology 2 (SH2) domain which binds phospholipase C (PLC)gamma 2, and a COOH-terminal pleckstrin homology (PH) domain. Thus, Bam32 may function to integrate protein tyrosine kinase (PTK) and phosphatidylinositol 3-kinase (PI3K) signaling pathways in B cells. To further define the role Bam32 plays in B cells, we generated Bam32-deficient DT40 cells. These Bam32(-/-) cells exhibited lower levels of B cell antigen receptor (BCR)-induced calcium mobilization with modest decreases in tyrosine phosphorylation of phospholipase C (PLC)gamma 2. Moreover, BCR-induced activation of extracellular signal-regulated kinase (ERK), c-jun NH2-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) pathways was impaired in Bam32(-/-) cells but not the activation of Akt-related pathways. Activation of downstream transcription factors such as nuclear factor of activated T cells (NF-AT) and nuclear factor of kappa binding (NF-kappa B) was also impaired in Bam32(-/-) cells. Furthermore, Bam32(-/-) cells were more susceptible to BCR-induced death. Taken together, these findings suggest that Bam32 functions to regulate BCR-induced signaling and cell survival most likely in germinal centers.
authors.affiliation: Department of Microbiology, University of Washington, Seattle, WA 98195, USA.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Niiro
authors.forename: Akito
authors.initials: A
authors.lastname: Maeda
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Kurosaki
authors.forename: Edward A
authors.initials: EA
authors.lastname: Clark
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology*; D001798:Blood Proteins; D020013:Calcium Signaling; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D002470:Cell Survival; D002478:Cells, Cultured; D002645:Chickens; D004268:DNA-Binding Proteins / Q000378:metabolism; D018858:Germinal Center / Q000276:immunology; D007527:Isoenzymes / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D051966:Phospholipase C gamma; D010750:Phosphoproteins; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D008565:Membrane Proteins; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011947:Receptors, Antigen, B-Cell; D014157:Transcription Factors; C039077:platelet protein P47; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D010738:Type C Phospholipases; D051966:Phospholipase C gamma