title: cAMP-mediated growth inhibition of lymphoid cells in G1: rapid down-regulation of cyclin D3 at the level of translation.
abstract: cAMP is an important physiological mediator of lymphoid growth inhibition. The purpose of the present study was to establish the link between cAMP and the cell cycle machinery leading to inhibition of G1/S transition in human peripheral blood lymphocytes (PBL). To unravel immediate effects of cAMP on this part of the cell cycle machinery, lymphocytes were synchronized in mid to late G1 after stimulation with phytohemaglutenin (PHA) for 32 h. We report that addition of forskolin or cAMP analogues to the cells resulted in dephosphorylation of retinoblastoma protein commencing as early as 30 min. A rapid effect of forskolin was noted on the activity of cyclin-dependent kinase (cdk) 4, which decreased significantly within 30 min of treatment. The decrease in cdk4 activity was concurrent with reduced levels of cyclin D3 protein and a decrease in the fraction of cdk4 associated with cyclin D3. The down-regulation of cyclin D3 was at the level of translation, and this event was preceded by a pronounced inhibition of Akt/protein kinase B phosphorylation at Ser 473. Taken together, our data imply that cyclin D3 is a major effector of cAMP-mediated inhibition of cell cycle progression in PBL, and that cAMP exerts its effect on cyclin D3 expression at the level of translation.
authors.affiliation: Institute of Medical Biochemistry, University of Oslo, Norway.
authors.forename: S
authors.initials: S
authors.lastname: Naderi
authors.forename: K B
authors.initials: KB
authors.lastname: Gützkow
authors.forename: J
authors.initials: J
authors.lastname: Christoffersen
authors.forename: E B
authors.initials: EB
authors.lastname: Smeland
authors.forename: H K
authors.initials: HK
authors.lastname: Blomhoff
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D056743:Cyclin D3; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000096:biosynthesis / Q000378:metabolism; D016213:Cyclins / Q000096:biosynthesis*; D015536:Down-Regulation; D016193:G1 Phase; D006801:Humans; D008214:Lymphocytes / Q000166:cytology* / Q000187:drug effects; D008869:Microtubule-Associated Proteins / Q000096:biosynthesis; D010766:Phosphorylation; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D016160:Retinoblastoma Protein / Q000378:metabolism; D016196:S Phase; D013873:Thionucleotides / Q000378:metabolism / Q000494:pharmacology; D025521:Tumor Suppressor Proteins
chemical_list: C105593:8-bromoadenosine-3',5'-cyclic monophosphorothioate; C534696:CCND3 protein, human; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D056743:Cyclin D3; D019927:Cyclin E; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D008869:Microtubule-Associated Proteins; D011518:Proto-Oncogene Proteins; D016160:Retinoblastoma Protein; D013873:Thionucleotides; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; C015929:8-((4-chlorophenyl)thio)cyclic-3',5'-AMP; D000242:Cyclic AMP; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D042846:CDC2-CDC28 Kinases; C495894:CDK2 protein, human; C495900:CDK4 protein, human; C495911:CDK6 protein, human; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D018844:Cyclin-Dependent Kinases