Roles of the intracellular regions of angiotensin II receptor AT2 in mediating reduction of intracellular cGMP levels.
Roles of the intracellular regions of angiotensin II receptor AT2 in mediating reduction of intracellular cGMP levels.
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血管紧张素 II 受体 AT2 的细胞内区域在介导细胞内 cGMP 水平降低中的作用。
DOI：
10.1016/j.cellsig.2004.08.007
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Gavini,Nara
中科院分区：
文献类型：
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作者：
Pulakat,Lakshmi;Rahman,Simi;Gray,Amanda;Knowle,Dieter;Gavini,Nara
我们之前已经证明，当被配体结合激活时，血管紧张素II （Ang II）受体AT2降低了非洲爪蟾卵母细胞内cGMP的水平，而AT2的c端细胞质尾部作为该功能的负调节因子。在这里，我们报道了AT2细胞内第2和第3环突变对AT2介导的cGMP还原的影响。突变与激活三聚体g蛋白g α亚基有关的第2 ICL的高度保守的DRY基序（D141G-R142G-Y143A）不影响at2介导的cGMP还原。此外，抗gi α抗体或磷酸二酯酶抑制剂IBMX没有抑制at2介导的cGMP还原，这表明gi α活化和随后的磷酸二酯酶活化与该功能无关。相比之下，位于AT2第3 ICL c端的突变T250R-R251N和L255F-K256R在酵母双杂交实验中保留了野生型AT2的配体结合特性和与ErbB3相互作用的能力，但破坏了AT2介导的cGMP还原。AT2的ICL在AT2介导的卵母细胞cGMP减少和AT2介导的cox -7细胞SHP1激活中的作用相似（需要第三ICL来实现功能和缺乏DRY基序的参与），表明这两种信号机制中的级联事件可能相似，卵母细胞特异性SHP1样蛋白可能参与这些细胞中AT2介导的cGMP减少。
We have shown previously that the angiotensin II (Ang II) receptor AT2 reduces the intracellular levels of cGMP in Xenopus oocytes when activated by ligand binding, and the C-terminal cytoplasmic tail of the AT2 acts as a negative regulator of this function. Here we report the effects of mutations in the 2nd and 3rd intracellular loops of AT2 on AT2-mediated cGMP reduction. Mutating the highly conserved DRY motif (D141G-R142G-Y143A) of the 2nd ICL implicated in activating Gαsubunit of trimeric G-proteins did not affect AT2-mediated cGMP reduction. Moreover, anti-Giαantibody or phosphodiesterase inhibitor IBMX did not inhibit AT2-mediated cGMP reduction, suggesting that Giαactivation and subsequent phosphodiesterase activation are not involved in this function. In contrast, mutations T250R-R251N and L255F-K256R located in the C-terminus of the 3rd ICL of AT2 retained ligand-binding properties of the wild-type AT2, and its ability to interact with the ErbB3 in yeast two-hybrid assay, but abolished AT2-mediated cGMP reduction. Similarities in the roles of ICLs of AT2 in AT2-mediated cGMP reduction in oocytes, and AT2-mediated SHP1 activation in COS-7 cells, (need of 3rd ICL for both functions and lack of involvement of DRY motif), suggest that the cascade of events in these two signaling mechanisms could be similar, and that an oocyte-specific SHP1-like protein may be involved in AT2-mediated cGMP reduction in these cells.