Angiotensin-(3-4) counteracts the Angiotensin II inhibitory action on renal Cap>2 +p>-ATPase through a cAMP/PKA pathway

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• 作者：Flavia Axelb ; Juliana Dias ; Filipe Mir ; a ; Fern ; a M. Ferr?o ; Rosana I. Reis ; Claudio M. Costa-Neto ; Lucienne S. Lara ; Adalberto Vieyra
• 关键词：ACE ; angiotensin converting enzyme ; Ang II ; angiotensin II ; Ang-(1&minus ; 7) ; angiotensin-(1&minus ; 7) ; Ang-(3&minus ; 4) ; Val3&minus ;   ; Tyr4 ; AT1R ; type 1 angiotensin II receptors ; AT2R ; type 2 angiotensin II receptors ; AT(1&minus ; 7)R(MAS) ; angiotensin-(1
• 刊名：Regulatory Peptides
• 出版年：2012
• 出版时间：20 August, 2012
• 年：2012
• 卷：177
• 期：1-3
• 页码：27-34
• 全文大小：615 K

文摘

We recently demonstrated that Angiotensin-(3?4) [Ang-(3?4)], an Ang II-derived dipeptide, overcomes inhibition of plasma membrane Cap>2 +p>-ATPase promoted by nanomolar concentrations of Ang II in basolateral membranes of renal proximal tubule cells, with involvement of a so far unknown AT₂R-dependent and NO-independent mechanism. The present study investigates the signaling pathway triggered by Ang-(3?4) that is responsible for counteracting the inhibitory effect of Ang II, and attempts to elucidate the functional interaction of the dipeptide with Ang II at the level of AT₂R. Stimulation by cholera toxin of G_s¦Á protein structurally linked to AT₂R ? as revealed by their co-immunoprecipitation ? mimicked the effect of Ang-(3?4) on Cap>2 +p>-ATPase activity. Furthermore, addition of dibutyril-cAMP (db-cAMP) mimicked Ang-(3?4), whereas the specific PKA inhibitor, PKAi_(5-24) peptide, suppressed the counter-regulatory effect of Ang-(3?4) and the AT₂R agonist, CGP42112A. Membrane-associated PKA activity was stimulated by Ang-(3?4) or CGP42112A to comparable levels as db-cAMP, and the Ang-(3-4) effect was abrogated by the AT₂R antagonist PD123319, whereas the AT₁R antagonist Losartan had no effect. Ang-(3?4) stimulated PKA-mediated phosphorylation of Cap>2 +p>-ATPase and activated PKA to comparable levels. Binding assays demonstrated that Ang-(3?4) could not displace p>p>3p>p>H-Ang II from HEK 293T cells expressing AT₂R, but 10p>? 10p> mol/L Ang-(3?4) resulted in the appearance of a probable higher-affinity site (picomolar range) for Ang II. The results presented herein demonstrate that Ang-(3?4), acting as an allosteric enhancer, suppresses Ang II-mediated inhibition of Cap>2 +p>-ATPase through an AT₂R/cAMP/PKA pathway, after inducing conformational changes in AT₂R that results in generation of higher-affinity sites for Ang II.