Structural determinants for the activation mechanism of the angiotensin II type 1 receptor differ for phosphoinositide hydrolysis and mitogen-activated protein kinase pathways
Structural determinants for the activation mechanism of the angiotensin II type 1 receptor differ for phosphoinositide hydrolysis and mitogen-activated protein kinase pathways
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DOI：
10.1016/s0006-2952(03)00257-0
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发表时间：
2003-07-15
影响因子：
5.8
通讯作者：
Yee, DK
中科院分区：
文献类型：
--
作者：
Hines, J;Fluharty, SJ;Yee, DK
虽然血管紧张素II I型受体（AT(1)受体）激活其经典效应物磷脂酶c - β (plc - β)的机制已经在很大程度上被阐明，但对于这种受体如何激活最近发现的效应物p42/44有丝分裂原激活蛋白激酶（p42/44(MAPK)），人们几乎没有达成共识。使用转染的COS-1细胞，我们在受体水平上研究了这一信号通路的激活。先前的突变研究依赖于磷酸肌苷周转率作为受体激活的指标，表明第二和第七跨膜结构域的关键残基参与AT(1)受体激活机制。因此，我们引入了多种突变-AT(1)[D74N]， AT(1)[Y292F]， AT(1)[N295S]和AT(1)[AT(2) TM7]，它们由AT(1)第七跨膜结构域与AT(1)对应物的嵌合取代组成。这些突变强烈削弱了受体激活plc - β的能力，但对其激活p42/44的能力几乎没有影响，这不仅表明p42/44并不完全位于G蛋白G(q)/ plc - β途径的下游，而且表明AT(1)受体可能存在不止一种激活状态。蛋白激酶C抑制剂无法阻断AT(1)受体对p42/44 MAPK的激活，进一步证实了受体对p42/44（MAPK）的激活在很大程度上独立于G(q)/ plc - β /PKC途径。综上所述，实验证据强烈表明，AT(1)受体激活p42/44 MAPK的机制与plc - β的机制根本不同，即使在受体本身的水平上也是如此。(C) 2003爱思唯尔科学有限公司版权所有。
While the mechanism whereby the angiotensin II type I receptor (AT(1) receptor) activates its classical effector phospholipase C-beta (PLC-beta) has largely been elucidated, there is little consensus on how this receptor activates a more recently identified effector, the p42/44 mitogen-activated protein kinases (p42/44(MAPK)). Using transfected COS-1 cells, we investigated the activation of this signaling pathway at the receptor level itself. Previous mutational studies that relied on phosphoinositide turnover as an index of receptor activation have indicated that key residues in the second and seventh transmembrane domains participate in AT(1) receptor activation mechanisms. Thus, we introduced a variety of mutations-AT(1)[D74N], AT(1)[Y292F], AT(1)[N295S], and AT(1)[AT(2) TM7], which is composed of a chimeric substitution of the AT(1) seventh transmembrane domain with its AT(1) counterpart. These mutations that strongly diminished the receptor's ability to activate PLC-beta had little to no effect on its ability to activate p42/44, which not only suggests that p42/44 does not exclusively lie downstream of the G-protein G(q)/PLC-beta pathway but also indicates that more than one activation state may exist for the AT(1) receptor. The failure of a protein kinase C inhibitor to block AT(1) receptor activation of p42/44 MAPK further corroborated evidence that the receptor's activation of p42/44(MAPK) is largely independent of the G(q)/PLC-beta/PKC pathway. Taken together, the experimental evidence strongly suggests that the mechanism whereby the AT(1) receptor activates p42/44 MAPK is fundamentally different from that for PLC-beta, even at the level of the receptor itself. (C) 2003 Elsevier Science Inc. All rights reserved.