Gildea John J, Wang Xiaoli, Jose Pedro A, Felder Robin A
Department of Pathology, University of Virginia, Charlottesville, VA 22908, USA.
Hypertension. 2008 Feb;51(2):360-6. doi: 10.1161/HYPERTENSIONAHA.107.100099. Epub 2008 Jan 2.
Renal sodium transport is increased by the angiotensin type 1 receptor (AT(1)R), which is counterregulated by dopamine via unknown mechanisms involving either the dopamine type 1 (D(1)R) or dopamine type 5 receptor (D(5)R) that belong to the D(1)-like receptor family of dopamine receptors. We hypothesize that the D(1)R and D(5)R differentially regulate AT(1)R protein expression and signaling, which may have important implications in the pathogenesis of essential hypertension. D(1)R and D(5)R share the same agonists and antagonists; therefore, the selective effects of either D(1)R or D(5)R stimulation on AT(1)R expression in human renal proximal tubule cells were determined using antisense oligonucleotides selective to either D(1)R or D(5)R. We also determined the role of receptor tyrosine kinase and the proteosome on the D(1)R/D(5)R-mediated effects on AT(1)R expression and internalization. In renal proximal tubule cells, D(5)R (not D(1)R) decreased AT(1)R expression (half-life: 0.47+/-0.18 hours) and AT(1)R-mediated extracellular signal-regulated kinase 1/2 phosphorylation (232+/-18.9 U with angiotensin II [10(-7) mol/L] versus 81+/-8.9 U with angiotensin II [10(-7) mol/L] and fenoldopam [D(1)R/D(5)R agonist; 10(-6) mol/L; P<0.05; n=6). The fenoldopam-induced decrease in AT(1)R expression was reversed by 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo (3,4-d) pyrimidine (c-Src tyrosine-kinase inhibitor) and clasto-lactacystin beta-lactone (proteasome inhibitor), demonstrating that the fenoldopam-mediated decrease in total cell AT(1)R expression is a result of a c-Src- and proteasome-dependent process. D(5)R stimulation decreases AT(1)R expression and is c-Src and proteasome dependent. The discovery of differential regulation by D(1)R and D(5)R opens new avenues for the development of agonists selective to either receptor subtype as targeted antihypertensive agents that can decrease AT(1)R-mediated antinatriuresis.
1型血管紧张素受体（AT(1)R）可增加肾脏钠转运，多巴胺通过涉及多巴胺1型（D(1)R）或多巴胺5型受体（D(5)R）的未知机制对其进行反向调节，D(1)R和D(5)R属于多巴胺受体的D(1)样受体家族。我们假设D(1)R和D(5)R对AT(1)R蛋白表达和信号传导有不同的调节作用，这可能对原发性高血压的发病机制具有重要意义。D(1)R和D(5)R具有相同的激动剂和拮抗剂；因此，使用对D(1)R或D(5)R具有选择性的反义寡核苷酸，确定了D(1)R或D(5)R刺激对人肾近端小管细胞中AT(1)R表达的选择性作用。我们还确定了受体酪氨酸激酶和蛋白酶体在D(1)R/D(5)R介导的对AT(1)R表达和内化的影响中的作用。在肾近端小管细胞中，D(5)R（而非D(1)R）降低了AT(1)R表达（半衰期：0.47±0.18小时）以及AT(1)R介导的细胞外信号调节激酶-1/2磷酸化（血管紧张素II [10(-7) mol/L]时为232±18.9 U，而血管紧张素II [10(-7) mol/L]和非诺多泮[D(1)R/D(5)R激动剂；10(-6) mol/L]时为81±8.9 U；P<0.05；n = 6）。4-氨基-5-（4-氯苯基）-7-（叔丁基）吡唑并（3,4-d）嘧啶（c-Src酪氨酸激酶抑制剂）和氯抑素β-内酯（蛋白酶体抑制剂）可逆转非诺多泮诱导的AT(1)R表达降低，表明非诺多泮介导的总细胞AT(1)R表达降低是c-Src和蛋白酶体依赖性过程的结果。D(5)R刺激可降低AT(1)R表达，且是c-Src和蛋白酶体依赖性的。D(1)R和D(5)R的差异调节发现为开发对任一受体亚型具有选择性的激动剂开辟了新途径，这些激动剂可作为靶向抗高血压药物，减少AT(1)R介导的尿钠排泄减少。
