title: Regulation of p27Kip1 accumulation in murine B-lymphoma cells: role of c-Myc and calcium.
abstract: IgM cross-linking induces G1 arrest and apoptosis in murine B-lymphoma cells. It prevents pRb phosphorylation by decreasing cyclin-dependent kinase 2 activity via the up-regulation of cyclin kinase inhibitor p27Kip1. Anti-IgM also causes an increase in cytosolic free calcium and a loss of c-myc mRNA and protein. This down-regulation of c-Myc is prevented by CD40L, which rescues cells from anti-IgM-induced apoptosis. In this study, we addressed the mechanism(s) of anti-IgM-induced p27Kip1 accumulation. We examined effects of early events in B-cell receptor-mediated signaling, c-Myc down-regulation, and an increase in free calcium on p27Kip1. Down-regulation of c-myc alone had no effect on p27Kip1; neither did an increase in free calcium alone. Together, these two events led to p27Kip1 induction, growth arrest, and apoptosis. CD40L, the calcium chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester, and cyclosporin A all prevented anti-IgM-induced p27Kip1 accumulation, suggesting that both the decrease in c-Myc expression and an increase in free calcium are necessary for p27Kip1 up-regulation.
authors.affiliation: Department of Immunology, Holland Laboratory for the Biomedical Sciences, American Red Cross, Rockville, Maryland 20855, USA.
authors.forename: D
authors.initials: D
authors.lastname: Donjerković
authors.forename: L
authors.initials: L
authors.lastname: Zhang
authors.forename: D W
authors.initials: DW
authors.lastname: Scott
mesh_terms: D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D023201:CD40 Ligand; D002118:Calcium / Q000378:metabolism*; D061945:Caspase Inhibitors; D018797:Cell Cycle Proteins; D002460:Cell Line; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016572:Cyclosporine / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000378:metabolism; D016193:G1 Phase; D016147:Genes, Tumor Suppressor; D007075:Immunoglobulin M / Q000494:pharmacology; D016393:Lymphoma, B-Cell / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D007075:Immunoglobulin M; D008562:Membrane Glycoproteins; D008869:Microtubule-Associated Proteins; D016271:Proto-Oncogene Proteins c-myc; D025521:Tumor Suppressor Proteins; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D023201:CD40 Ligand; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016572:Cyclosporine; D018844:Cyclin-Dependent Kinases; D002118:Calcium