Glucocorticoids induce G1 as well as S-phase lengthening in normal human stimulated lymphocytes: differential effects on cell cycle regulatory proteins.
In order to analyze dexamethasone effects on peripheral blood lymphocyte proliferation, we defined various experimental conditions: dexamethasone introduced (i) at the time of phytohemagglutinin stimulation, (ii) 48 h after the beginning of phytohemagglutinin stimulation, and (iii) on unstimulated lymphocytes. In stimulated lymphocytes, we observed an early G1 accumulation (P < 0.005), a delayed increase in the duration of S-phase (P < 0.03), and a consequent increase in cell-cycle duration. The expression of several cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors (CKIs) was modified. Cyclin D3, CDK4, and CDK6 involved in G1-phase control were significantly decreased under dexamethasone treatment whatever the level of stimulation of lymphocytes (stimulated or unstimulated PBL). Cyclin E and CDK2, acting in G1/ S-phase transition and S-phase regulation, decreased in stimulated lymphocytes before any modification of S-phase (P < 0.002). The expression of CKIs, mainly of p27Kip1, appeared to vary with the degree of cell stimulation: a decrease was observed on treated unstimulated lymphocytes, while p27Kip1 increased in dexamethasone-treated cells during stimulation. Our results indicate sequential modifications of the cell-cycle regulation by dexamethasone starting with an action on G1 followed by S-phase control modifications. The protein analysis pinpoints the major complexes concerned: CDK4 and CDK6/cyclin D are mainly involved in G1-phase modifications, while CDK2 and its partner, cyclin E, might be specifically involved in the lengthening of S-phase. The variations observed for p27Kip1 might amplify the functional effects of dexamethasone on kinasic complexes.
Baghdassarian
N
N
Faculté de Médecine, Laboratoire de Cytologie Analytique, Lyon, France.
Catallo
R
R
Mahly
M A
MA
Ffrench
P
P
Chizat
F
F
Bryon
P A
PA
Ffrench
M
M
D017209:Apoptosis; D016203:CDC2 Protein Kinase / Q000378:metabolism; D042846:CDC2-CDC28 Kinases; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002478:Cells, Cultured; D056743:Cyclin D3; D019927:Cyclin E / Q000378:metabolism; D051357:Cyclin-Dependent Kinase 2; D051358:Cyclin-Dependent Kinase 4; D051361:Cyclin-Dependent Kinase 6; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D016213:Cyclins / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology*; D016193:G1 Phase; D005938:Glucocorticoids / Q000494:pharmacology*; D006131:Growth Inhibitors / Q000494:pharmacology*; D006801:Humans; D008214:Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008934:Mitogens / Q000494:pharmacology; D010835:Phytohemagglutinins / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D016196:S Phase; D025521:Tumor Suppressor Proteins
C534696:CCND3 protein, human; D018797:Cell Cycle Proteins; D056743:Cyclin D3; D019927:Cyclin E; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016213:Cyclins; D005938:Glucocorticoids; D006131:Growth Inhibitors; D008869:Microtubule-Associated Proteins; D008934:Mitogens; D010835:Phytohemagglutinins; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D003907:Dexamethasone; D017346:Protein Serine-Threonine Kinases; D016203:CDC2 Protein Kinase; 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