Altered regulation of G1 cyclins in oxidant-induced growth arrest of lung alveolar epithelial cells. Accumulation of inactive cyclin E-DCK2 complexes.
The alveolar surface of the lung is a major target for oxidant injury, and its repair following injury is dependent on the ability of its stem cells, the type 2 cells, to initiate proliferation. From previous studies it is likely that events located before the entry into the S phase of the cell cycle and involving several components of the insulin-like growth factor system as well as of transforming growth factor-beta (TGF-beta) play a key role in growth regulation of oxidant-exposed type 2 epithelial cells. To gain further insights into these mechanisms, we explored the effects of O2 exposure on G1 cyclins and their cyclin-dependent kinases (CDKs). We documented an increased expression of these genes in O2-treated type 2 cells. However, despite this induction, a dramatic decrease in cyclin E-CDK2 activity, but not in cyclin D-CDK4 activity, was found. The concomitant induction of CDK inhibitory proteins (CKIs), mainly p21(CIP1), suggests that accumulation of inactive cyclin E-CDK2 activity is due to CKI binding. We also provided evidence that the mechanisms regulating this process involved TGF-beta as anti-TGF-beta antibody treatment was able to reduce the oxidant-induced inhibition of cyclin E-CDK2 activity. Taken together, these results suggest that oxidants may block entry into S phase by acting on a subset of late G1 events whose alterations are sufficient to impair the activation of cyclin E-CDK2 complexes.
Corroyer
S
S
Physiology Department, Trousseau Hospital, St. Antoine Medical School, University of Paris, 75012 Paris, France.
Maitre
B
B
Cazals
V
V
Clement
A
A
D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D019938:Cyclin D1; D056742:Cyclin D2; D056743:Cyclin D3; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis*; D017931:DNA Primers; D004791:Enzyme Inhibitors; D004847:Epithelial Cells; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism; D016193:G1 Phase; D008969:Molecular Sequence Data; D015513:Oncogene Proteins / Q000096:biosynthesis; D016877:Oxidants / Q000494:pharmacology*; D010100:Oxygen / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D011650:Pulmonary Alveoli / Q000166:cytology* / Q000378:metabolism*; D051381:Rats; D018125:Receptors, Transforming Growth Factor beta / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000276:immunology / Q000494:pharmacology
D000906:Antibodies; C486197:Ccnd2 protein, rat; C534698:Ccnd3 protein, rat; C493958:Cdkn1a protein, rat; D056742:Cyclin D2; D056743:Cyclin D3; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D017931:DNA Primers; D004791:Enzyme Inhibitors; D015513:Oncogene Proteins; D016877:Oxidants; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; D019938:Cyclin D1; D010100:Oxygen