title: B cell antigen receptor-induced activation of Akt promotes B cell survival and is dependent on Syk kinase.
abstract: Signaling through the B cell Ag receptor (BCR) is a key determinant in the regulation of B cell physiology. Depending on additional factors, such as microenvironment and developmental stage, ligation of the BCR can trigger B lymphocyte activation, proliferation, or apoptosis. The regulatory mechanisms determining B cell apoptosis and survival are not known. Using the chicken B lymphoma cell line DT40 as a model system, we investigated the role of the serine/threonine kinase Akt in B cell activation. While parental DT40 cells undergo apoptosis in response to BCR cross-linking, cells overexpressing Akt show a greatly diminished apoptotic response. By contrast, limiting the activation of Akt, either by inhibiting phosphatidylinositol 3-kinase or by ectopic expression of the phospholipid phosphatase MMAC1, results in a significant increase in the percentage of apoptotic cells after BCR cross-linking. Using various DT40 knockout cell lines, we further demonstrate that the tyrosine kinase Syk is required for Akt activation and that Lyn tyrosine kinase inhibits Akt activation. Taken together, the data demonstrate that Akt plays an important role in B cell survival and that Akt is activated in a Syk-dependent pathway.
authors.affiliation: Department of Cell Signaling, DNAX Research Institute, Palo Alto, CA 94304, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Pogue
authors.forename: T
authors.initials: T
authors.lastname: Kurosaki
authors.forename: J
authors.initials: J
authors.lastname: Bolen
authors.forename: R
authors.initials: R
authors.lastname: Herbst
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000276:immunology; D001402:B-Lymphocytes / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000276:immunology; D002645:Chickens; D002867:Chromones / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects / Q000276:immunology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004792:Enzyme Precursors / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D009025:Morpholines / Q000494:pharmacology; D051059:PTEN Phosphohydrolase; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000096:biosynthesis; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt; D011947:Receptors, Antigen, B-Cell / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000276:immunology; D000072377:Syk Kinase; D025521:Tumor Suppressor Proteins
chemical_list: D002867:Chromones; D004791:Enzyme Inhibitors; D004792:Enzyme Precursors; D047908:Intracellular Signaling Peptides and Proteins; D009025:Morpholines; D011518:Proto-Oncogene Proteins; D011947:Receptors, Antigen, B-Cell; D025521:Tumor Suppressor Proteins; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D010744:Phosphoric Monoester Hydrolases; D051059:PTEN Phosphohydrolase