Negative regulation of gamma-globin gene expression by cyclic AMP-dependent pathway in erythroid cells.
OBJECTIVE
Fetal hemoglobin inducers such as hemin, butyrate, and hydroxyurea stimulate gamma-globin gene expression by activating the cyclic GMP (cGMP)-dependent pathway. Although cGMP activates the cyclic AMP (cAMP)-dependent pathway by suppressing cGMP-inhibited phosphodiesterase 3 (PDE3), the effects of the cAMP-dependent pathway on gamma-globin gene expression are unknown.


METHODS
The cAMP-dependent pathway was activated in K562 cells using the adenylate cyclase activator forskolin. Expression of gamma-globin mRNA was examined by primer extension, and transcriptional activity of the gamma-globin gene promoter was determined by reporter gene assays.


RESULTS
PDE3 was expressed in K562 cells at a high level. The cAMP-dependent pathway was found to be activated in K562 cells in which the cGMP-dependent pathway was activated by hemin. Activation of the cAMP-dependent pathway by forskolin inhibited hemin-induced expression of gamma-globin mRNA and decreased transcriptional activity of the gamma-globin gene promoter. The levels of phosphorylation of mitogen-activated protein kinases (MAPKs) were not affected by the cAMP-dependent pathway.


CONCLUSIONS
These results suggested that the cAMP-dependent pathway, which is independent of MAPK pathways, plays a negative role in gamma-globin gene expression in K562 cells. cAMP and cGMP may have differential roles in the regulation of gamma-globin gene expression in erythroid cells.
Laboratory of Molecular Hematology, Center for Human Genetics, Boston University School of Medicine, Boston, Mass. 02118-2394, USA.
Akio
A
Inoue
Yuichi
Y
Kuroyanagi
Kiminori
K
Terui
Paolo
P
Moi
Tohru
T
Ikuta
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology; D006152:Cyclic GMP / Q000502:physiology; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D015672:Erythroid Precursor Cells / Q000187:drug effects / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005914:Globins / Q000096:biosynthesis* / Q000235:genetics; D006427:Hemin / Q000494:pharmacology; D006801:Humans; D020014:K562 Cells / Q000187:drug effects / Q000378:metabolism; D020935:MAP Kinase Signaling System; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D014158:Transcription, Genetic
D017362:Cyclic AMP Response Element-Binding Protein; D012333:RNA, Messenger; C017759:9-(tetrahydro-2-furyl)-adenine; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D006427:Hemin; D005914:Globins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D054684:Cyclic Nucleotide Phosphodiesterases, Type 3; D000262:Adenylyl Cyclases; D006152:Cyclic GMP; D000225:Adenine