Transcriptional modulation of platelet-activating factor receptor gene expression by cyclic AMP.
We examined the effects of increasing intracellular cyclic AMP levels on the expression of human PAF receptor (hPAF-R). Peripheral blood monocytes constitutively expressed hPAF-R mRNA transcripts. A transiently elevated intracellular concentration of AMP induced with prostaglandin E2, cholera toxin, or forskolin was a sufficient signal to inhibit PAF-R expression. To determine the mechanisms of this inhibition, human monocytes were treated with dibutyryl cAMP, a cell-permeable cAMP analogue. cAMP reduced the expression of hPAF-R in a concentration- and a time-dependent manner. The effect was seen as early as 1 h and was essentially total by 4 h. Stability of hPAF-R mRNA was not markedly decreased by cAMP, as assessed by measuring the half-lives of the transcripts. Moreover, the nuclear transcription rate of the hPAF-R gene was reduced as early as 30 min after stimulation with cAMP. The inhibition of hPAF-R mRNA accumulation was associated with diminished responsiveness to PAF, as assayed by intracellular Ca2+ fluxes, decreased number of binding sites, and decreased hPAF-R protein expression on the cell surface, as assessed by flow cytometry using a polyclonal anti-hPAF-R antibody. These data indicate that PAF-R expression can be regulated at the transcriptional and possibly post-transcriptional levels by elevation of intracellular cAMP.
Department of Pediatrics, Faculty of Medicine, University of Sherbrooke, Québec, Canada.
M
M
Thivierge
N
N
Alami
E
E
Müller
A J
AJ
de Brum-Fernandes
M
M
Rola-Pleszczynski
D000818:Animals; D001381:Azepines / Q000378:metabolism; D003994:Bucladesine / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D006224:Cricetinae; D000242:Cyclic AMP / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D015232:Dinoprostone / Q000502:physiology; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D009000:Monocytes / Q000378:metabolism; D010972:Platelet Activating Factor / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger / Q000096:biosynthesis; D011956:Receptors, Cell Surface / Q000096:biosynthesis / Q000235:genetics*; D043562:Receptors, G-Protein-Coupled; D014158:Transcription, Genetic; D014230:Triazoles / Q000378:metabolism
D001381:Azepines; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D012333:RNA, Messenger; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D014230:Triazoles; C039351:platelet activating factor receptor; C052518:WEB 2086; D003994:Bucladesine; D003513:Cycloheximide; D000242:Cyclic AMP; D015232:Dinoprostone; D002118:Calcium