cAMP enhances CSF-1-induced ERK activity and c-fos mRNA expression via a MEK-dependent and Ras-independent mechanism in macrophages.
Inhibition of MAPK by elevated intracellular cAMP has often been correlated with suppression of growth factor-induced proliferation. However, in murine bone marrow-derived macrophages (BMM) we show that the cAMP analogue, 8-bromo cAMP (8BrcAMP) (1mM), despite being a dramatic G1 phase proliferation inhibitor, increased ERK activity both in the absence and presence of CSF-1; these increases were blocked by PD98059 (100 microM) suggesting MEK dependence. In contrast, CSF-1-stimulated p21Ras activity was blocked by 8BrcAMP thus correlating with the inhibition of proliferation. This is the first report to indicate that elevated intracellular cAMP can activate ERK activity while inhibiting proliferation and the data support the concept in CSF-1-treated macrophages of Ras-independent activation of ERK activity. It was also found that the acute but not the sustained elevation of c-fos mRNA expression due to 8BrcAMP was also MEK dependent indicating that there are separate pathways controlling c-fos mRNA expression in BMM.
Wilson
N J
NJ
University of Melbourne, Department of Medicine, Royal Melbourne Hospital, Parkville, Australia.
Jaworowski
A
A
Ward
A C
AC
Hamilton
J A
JA
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D001854:Bone Marrow Cells / Q000187:drug effects / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos; D048369:MAP Kinase Kinase 1; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D008808:Mice, Inbred CBA; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism
D012333:RNA, Messenger; D015124:8-Bromo Cyclic Adenosine Monophosphate; D016173:Macrophage Colony-Stimulating Factor; D000242:Cyclic AMP; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases; D018631:ras Proteins