Reconstitution of angiotensin receptor mRNA down-regulation in vascular smooth muscle. Post-transcriptional control by protein kinase a but not mitogenic signaling directed by the 5'-untranslated region.
Cell surface receptor activation generally leads to changes in mRNA abundance, which may involve regulatory targets in processes working at the post-transcriptional level. Many types of agonists down-regulate vascular smooth muscle angiotensin receptor (AT(1)-R) gene expression, but it is unclear which of these activate post-transcriptional mechanisms. To reconstitute faithfully the normal AT(1)-R mRNA regulatory environment, tetracycline-suppressible promoters drive highly accurate recombinant AT(1)-R mRNA mimics in vascular smooth muscle cells that co-express an endogenous AT(1)-R mRNA. Down-regulation of the latter occurs shortly after stimulating mitogenic receptors or by using forskolin, but only cAMP signaling reduces expression of the recombinant AT(1)-R mRNA. Transcription of the recombinant mRNA is unaffected by cAMP signaling. Deletions of the AT(1)-R mRNA 3'-untranslated region do not impair cAMP-mediated down-regulation. Both loss of function and gain of function mutants show the response is mediated by the 5'-untranslated region. These observations provide the first direct functional evidence for modulation of vascular AT(1)-R gene expression by a mechanism involving a protein kinase A-regulated post-transcriptional process.
Xu
K
K
Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Murphy
T J
TJ
D000818:Animals; D001011:Aorta / Q000166:cytology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D015536:Down-Regulation; D006207:Half-Life; D008934:Mitogens / Q000494:pharmacology; D008938:Mitosis; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009154:Mutation; D012323:RNA Processing, Post-Transcriptional; D020871:RNA Stability; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000235:genetics*; D015398:Signal Transduction; D013754:Tetracyclines / Q000494:pharmacology; D020506:Untranslated Regions / Q000378:metabolism
D008934:Mitogens; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D013754:Tetracyclines; D020506:Untranslated Regions; D005576:Colforsin; C016229:4-epianhydrotetracycline; D017868:Cyclic AMP-Dependent Protein Kinases