title: BCR targets cyclin D2 via Btk and the p85alpha subunit of PI3-K to induce cell cycle progression in primary mouse B cells.
abstract: The p85alpha subunit of PI3-K and Btk are two crucial components of the B-cell receptor (BCR) signalling pathway. In the present study, we showed that primary splenic B cells from p85alpha null and xid (Btk-deficient) mice fail to induce cyclin D2 expression and enter early G1, but not S phase of the cell cycle in response to BCR engagement. Furthermore, these Btk or p85alpha null B cells displayed increased cell death compared with wild type following BCR engagement. These findings are further confirmed by studies showing that specific pharmacological inhibitors of Btk (LFM-A13), PI3-K (LY294002 and Wortmannin) and PLCgamma (U73122) also block cyclin D2 expression and S phase entry following BCR stimulation, as well as triggering apoptosis. Collectively, these data provide evidence for the concept that the B-cell signalosome (p85alpha, Btk, BLNK and PLCgamma) is involved in regulating cyclin D2 expression in response to BCR engagement. PKC and intracellular calcium are two major downstream effectors of the B-cell signalosome and can be activated by PMA and ionomycin, respectively. In small resting (G0) B cells, costimulation with PMA and ionomycin, but not PMA or ionomycin alone, induces cyclin D2 expression and cell-cycle progression. Consistent with this, we also showed that the BCR-mediated cyclin D2 induction could be abolished by pretreatment of resting B cells with specific inhibitors of capacitative Ca(2+) entry (SK&F 96365) or PKC (Gö6850). Our present results lead us to propose a model in which the B-cell signalosome targets cyclin D2 via the Ca(2+) and PKC-dependent signalling cascades to mediate cell-cycle progression in response to BCR engagement.
authors.affiliation: Cancer Research-UK Labs and Section of Cancer Cell Biology, Department of Cancer Medicine, Imperial College School of Medicine at Hammersmith Hospital, Londom, UK.
authors.forename: Janet
authors.initials: J
authors.lastname: Glassford
authors.forename: Inês
authors.initials: I
authors.lastname: Soeiro
authors.forename: Sara M
authors.initials: SM
authors.lastname: Skarell
authors.forename: Lolita
authors.initials: L
authors.lastname: Banerji
authors.forename: Mary
authors.initials: M
authors.lastname: Holman
authors.forename: Gerry G B
authors.initials: GG
authors.lastname: Klaus
authors.forename: Takashi
authors.initials: T
authors.lastname: Kadowaki
authors.forename: Shigeo
authors.initials: S
authors.lastname: Koyasu
authors.forename: Eric W-F
authors.initials: EW
authors.lastname: Lam
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000577:Amides / Q000494:pharmacology; D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology; D017209:Apoptosis; D001402:B-Lymphocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology; D002453:Cell Cycle / Q000502:physiology; D002867:Chromones / Q000494:pharmacology; D058544:Class Ib Phosphatidylinositol 3-Kinase; D003433:Crosses, Genetic; D056742:Cyclin D2; D016213:Cyclins / Q000096:biosynthesis* / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D007093:Imidazoles / Q000494:pharmacology; D007153:Immunologic Deficiency Syndromes / Q000235:genetics / Q000276:immunology / Q000473:pathology*; D007211:Indoles / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D046911:Macromolecular Substances; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D018448:Models, Immunological; D009025:Morpholines / Q000494:pharmacology; D009570:Nitriles / Q000494:pharmacology; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D010750:Phosphoproteins / Q000502:physiology; D010766:Phosphorylation; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D011947:Receptors, Antigen, B-Cell / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000502:physiology; D019061:src-Family Kinases / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000077329:Agammaglobulinaemia Tyrosine Kinase; D000577:Amides; D000888:Antibodies, Anti-Idiotypic; D002352:Carrier Proteins; D002867:Chromones; D058544:Class Ib Phosphatidylinositol 3-Kinase; D056742:Cyclin D2; D016213:Cyclins; D004791:Enzyme Inhibitors; D007093:Imidazoles; D007211:Indoles; D015759:Ionomycin; D007527:Isoenzymes; D046911:Macromolecular Substances; D008301:Maleimides; D009025:Morpholines; D009570:Nitriles; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051966:Phospholipase C gamma; D010750:Phosphoproteins; D021122:Protein Subunits; D011505:Protein-Tyrosine Kinases; D011947:Receptors, Antigen, B-Cell; D013755:Tetradecanoylphorbol Acetate; D010738:Type C Phospholipases; D019061:src-Family Kinases; C113939:B cell linker protein; C486196:Ccnd2 protein, mouse; C118451:LFM A13; C044203:anti-IgM; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C546764:Pik3cg protein, mouse; C000625951:Btk protein, mouse; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C070515:bisindolylmaleimide I