Inhibition of cyclic AMP-dependent kinase by expression of a protein kinase inhibitor/enhanced green fluorescent fusion protein attenuates angiotensin II-induced type 1 AT1 receptor mRNA down-regulation in vascular smooth muscle cells.
Expression of the angiotensin II type 1 receptor (AT1-R) mRNA in vascular smooth muscle cells (VSMC) is down-regulated by a variety of agonists, including growth factors, agonists of Galphaq protein-coupled receptors, and activators of adenylyl cyclase. To determine whether cAMP-dependent protein kinases (PKA) participates in AT1-R mRNA down-regulation controlled by multiple classes of receptors, a PKA inhibitor peptide (PKIalpha) was developed and expressed in rat VSMC as a fusion with the enhanced green fluorescent protein (eGFP). PKA activity elicited both by forskolin and angiotensin II is suppressed in cells expressing this fusion protein (PKIalpha-eGFP), but platelet-derived growth factor-BB does not stimulate PKA activity in this preparation. PKIalpha-eGFP expression fully inhibits the forskolin-stimulated down-regulation of AT1-R mRNA levels and blocks 50% of the effect elicited by angiotensin II. This indicates that PKA plays a substantial role in angiotensin II-stimulated AT1-R mRNA down-regulation. However, inhibition of PKA has no effect on AT1-R mRNA down-regulation caused by platelet-derived growth factor-BB. These findings show how agonists such as angiotensin II that are not normally considered as activators of PKA can use PKA-dependent processes to modulate gene expression. These findings also provide definitive evidence that PKA-dependent pathways are involved in modulation of AT1-R mRNA levels in VSMC.
Wang
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Department of Pharmacology, Emory University School of Medicine, and Program in Molecular Therapeutics and Toxicology, Graduate Division of Biological and Biomedical Sciences, Emory University, Atlanta, Georgia 30322, USA.
Murphy
T J
TJ
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D000077214:Becaplermin; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors*; D015536:Down-Regulation / Q000502:physiology; D049452:Green Fluorescent Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000096:biosynthesis*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D015533:Transcriptional Activation / Q000502:physiology
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D011993:Recombinant Fusion Proteins; C015482:protein kinase modulator; D000804:Angiotensin II; D049452:Green Fluorescent Proteins; D000077214:Becaplermin; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases