title: Enhanced angiotensin receptor type 1 mRNA degradation and induction of polyribosomal mRNA binding proteins by angiotensin II in vascular smooth muscle cells.
abstract: Stimulation of cultured rat thoracic aorta vascular smooth muscle cells (VSMCs) with 100 nM angiotensin II (Ang II) reduces angiotensin receptor type 1 (AT1-R) gene expression. mRNA levels are reduced to approximately 30% of control levels 4 hr after the addition of Ang II to the culture medium. The loss of mRNA remains sustained for up to 24 hr after the addition of Ang II. The half-life of the AT1-R mRNA is approximately 2 hr in cells treated with a single dose of 100 nM Ang II. This represents a 3-fold reduction from its half-life of 6 hr in nonstimulated cells, as assessed by treatment with 5,6-dichlorobenzimidazole or actinomycin D to block transcription. Thus, the AT1-R mRNA is moderately unstable in VSMC and destabilized further by treatment with Ang II. Ang II-induced AT1-R mRNA destabilization is prevented by pretreatment with transcriptional inhibitors or the protein synthesis inhibitor cycloheximide, suggesting that Ang II-induced AT1-R mRNA destabilization requires the induction of an unknown factor or factors that are postulated to mediate this effect. AT1-R mRNA levels decrease more rapidly in vitro from a polyribosomal fraction isolated from VSMC exposed for 2 hr to 100 nM Ang II compared with that from vehicle-treated cells, suggesting that polyribosomal-associated AT1-R mRNA is at least one site of action for the mRNA destabilization effect of Ang II. Ang II stimulation induces a complex of polyribosomal proteins that bind specifically in the distal 350 bases of the AT1-R mRNA. Regulation of mRNA stability accounts in part for modulation of AT1-R gene expression by Ang II in VSMCs, and Ang II-induced AT1-R mRNA polyribosomal binding proteins are associated with this phenomenon.
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: G
authors.initials: G
authors.lastname: Nickenig
authors.forename: T J
authors.initials: TJ
authors.lastname: Murphy
mesh_terms: D000803:Angiotensin I / Q000378:metabolism*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D001345:Autoradiography; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004355:Drug Stability; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism*; D011132:Polyribosomes / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000096:biosynthesis*; D051381:Rats; D011945:Receptors, Angiotensin / Q000096:biosynthesis / Q000378:metabolism*; D013268:Stimulation, Chemical; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D000803:Angiotensin I; D003513:Cycloheximide