Activation of FoxO transcription factors contributes to the antiproliferative effect of cAMP.
cAMP is a potent inhibitor of cell proliferation in a variety of cell lines. Downregulation of cyclin D1 and upregulation of the cell cycle inhibitor p27Kip1 are two mechanisms by which cAMP may induce a G1-arrest. Here we show that cAMP inhibits proliferation of cells that constitutively express cyclin D1 or are deficient for Rb, demonstrating that changes in these cell cycle regulators do not account for the cAMP-induced growth effects in mouse embryo fibroblasts (MEFs). Interestingly, the antiproliferative effect of cAMP mimics the effect previously observed for FoxO transcription factors. These transcription factors are under negative control of protein kinase B (PKB). We show that in MEFs cAMP strongly induces transcriptional activation of FoxO4 through the inhibition of PKB. Accordingly, not only p27Kip1 but also the FoxO target MnSOD is upregulated by cAMP. Importantly, introduction of dominant-negative FoxO partially rescues cAMP-induced inhibition of proliferation. From these results we conclude that inhibition of PKB and subsequent activation of FoxO transcription factors mediates an antiproliferative effect of cAMP.
Kuiperij
H Bea
HB
Department of Physiological Chemistry and Centre for Biomedical Genetics, University Medical Center Utrecht, Universiteitsweg 100, 3584 CG Utrecht, The Netherlands.
van der Horst
Armando
A
Raaijmakers
Judith
J
Weijzen
Sanne
S
Medema
Rene H
RH
Bos
Johannes L
JL
Burgering
Boudewijn M T
BM
Zwartkruis
Fried J T
FJ
D016475:3T3 Cells; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D000242:Cyclic AMP / Q000494:pharmacology*; D019938:Cyclin D1 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051858:Forkhead Transcription Factors; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection
C436291:CDKN1B protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C108803:FOXO4 protein, human; D051858:Forkhead Transcription Factors; D047908:Intracellular Signaling Peptides and Proteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D000242:Cyclic AMP; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt