RESUMO
We describe a novel signaling mechanism mediated by the G-protein-coupled receptor (GPCR) angiotensin II (Ang II) type 2 receptor (AT(2)). Yeast two-hybrid studies and affinity column binding assay show that the isolated AT(2) C-terminus binds to the transcription factor promyelocytic zinc finger protein (PLZF). Cellular studies employing confocal microscopy show that Ang II stimulation induces cytosolic PLZF to co-localize with AT(2) at the plasma membrane, then drives AT(2) and PLZF to internalize. PLZF slowly emerges in the nucleus whereas AT(2) accumulates in the perinuclear region. Nuclear PLZF binds to a consensus sequence of the phosphatidylinositol-3 kinase p85 alpha subunit (p85 alpha PI3K) gene. AT(2) enhances expression of p85 alpha PI3K followed by enhanced p70(S6) kinase, essential to protein synthesis. An inactive mutant of PLZF abolishes this effect. PLZF is expressed robustly in the heart in contrast to many other tissues. This cardiac selective pathway involving AT(2), PLZF and p85 alpha PI3K may explain the absence of a cardiac hypertrophic response in AT(2) gene-deleted mice.
Assuntos
Cardiomegalia/genética , Cardiomegalia/fisiopatologia , Coração/fisiologia , Receptor Tipo 2 de Angiotensina/genética , Transdução de Sinais/fisiologia , Sequência de Aminoácidos , Animais , Células CHO , Cardiomegalia/prevenção & controle , Clonagem Molecular , Sequência Conservada , Cricetinae , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Escherichia coli/genética , Escherichia coli/metabolismo , Humanos , Fatores de Transcrição Kruppel-Like , Camundongos , Camundongos Knockout , Dados de Sequência Molecular , Fosfatidilinositol 3-Quinases/metabolismo , Proteína com Dedos de Zinco da Leucemia Promielocítica , Transporte Proteico , Ratos , Receptor Tipo 2 de Angiotensina/deficiência , Receptor Tipo 2 de Angiotensina/metabolismo , Proteínas Quinases S6 Ribossômicas/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transfecção , Dedos de ZincoRESUMO
Bainiku-ekisu, the fruit-juice concentrate of the Oriental plum (Prunus mume) has recently been shown to improve human blood fluidity. We have shown that angiotensin II (AngII) stimulates growth of vascular smooth muscle cells (VSMCs) through epidermal growth factor (EGF) receptor transactivation that involves reactive oxygen species (ROS) production. To better understanding the possible cardiovascular protective effect of Bainiku-ekisu, we have studied whether Bainiku-ekisu inhibits AngII-induced growth promoting signals in VSMCs. Bainiku-ekisu markedly inhibited AngII-induced EGF receptor transactivation. H(2)O(2)-induced EGF receptor transactivation was also inhibited by Bainiku-ekisu. Thus, Bainiku-ekisu markedly inhibited AngII-induced extracellular signal-regulated kinase (ERK) activation. However, EGF-induced ERK activation was not affected by Bainiku-ekisu. AngII stimulated leucine uptake in VSMCs that was significantly inhibited by Bainiku-ekisu. Also, Bainiku-ekisu possesses a potent antioxidant activity. Since the activation of EGF receptor, ERK and the production of ROS play central roles in mediating AngII-induced vascular remodeling, these data suggest that Bainiku-ekisu could exert a powerful cardiovascular protective effect with regard to cardiovascular diseases.