Stimulation by vasopressin of ERK phosphorylation and vector-driven water flux in astrocytes is transactivation-dependent.
Stimulation by vasopressin of ERK phosphorylation and vector-driven water flux in astrocytes is transactivation-dependent.
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DOI：
10.1016/j.ejphar.2008.03.030
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发表时间：
2008-06
影响因子：
5
通讯作者：
Ting Du;D. Song;Hongmei Li;Baoman Li;Liping Cai;L. Hertz;Liang Peng
中科院分区：
文献类型：
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作者：
Ting Du;D. Song;Hongmei Li;Baoman Li;Liping Cai;L. Hertz;Liang Peng
加压素作用于星形胶质细胞Gq蛋白和磷脂酶C偶联的V1受体。在也表达V1受体的系膜细胞中，它通过激活继发于表皮生长因子（EGF）受体反式激活的促分裂原活化蛋白激酶（MAP激酶）来刺激细胞生长。反式激活是细胞内/细胞外过程，其中Gq或Gi/o蛋白偶联受体的激活导致EGF受体激动剂的金属蛋白酶催化的脱落，其刺激相同细胞和/或其邻近细胞上的EGF受体。本研究的目的是调查，如果加压素信号转导介导的反式激活星形胶质细胞和是否需要这样的反式激活的能力，以促进矢量驱动的水通量。加压素浓度在10− 1/2和10− 6 M之间时，会导致细胞外调节激酶1和2（ERK 1/2）的磷酸化（活化）。ERK 1/2的磷酸化可被EGF受体激活的酪氨酸激酶抑制剂AG 1478或Zn ~（2+）激活的金属蛋白酶抑制剂GM 6001完全抑制，表明ERK 1/2的磷酸化与反式激活有关。暴露于低渗培养基中会立即（在1分钟内）导致细胞水体积增加（通过钙黄绿素荧光淬灭的减少来证明），其中一部分依赖于以1×10− 8 M浓度添加的加压素的存在。这种加压素依赖性成分在整个实验期间（22分钟）持续存在。加压素的作用在AG 1478的存在下被消除，表明其依赖于反式激活，并且被MAP激酶/ERK激酶（MEK）的抑制剂U 0126消除，从而消除ERK 1/2磷酸化。
Vasopressin acts on astrocytic Gqprotein- and phospholipase C-coupled V1receptors. In mesangial cells, which also express the V1receptor, it stimulates cell growth by activating mitogen-activated protein kinase (MAP kinase) secondary to transactivation of the epidermal growth factor (EGF) receptor. Transactivation is an intracellular/extracellular process, in which activation of a Gqor a Gi/oprotein-coupled receptor leads to metalloproteinase-catalyzed shedding of an EGF receptor agonist, which stimulates EGF receptors on the same cell and/or its neighbor(s). The goal of the present study was to investigate if vasopressin signaling is mediated by transactivation also in astrocytes and whether such a transactivation is required for its ability to facilitate vector-driven water fluxes. Vasopressin concentrations between 10−12and 10−6M were found to lead to phosphorylation (activation) of extracellular regulated kinase 1 and 2 (ERK1/2). Phosphorylation of ERK1/2could be completely inhibited by either AG1478, an inhibitor of the EGF receptor-activated tyrosine kinase, or GM6001, an inhibitor of Zn2+-activated metalloproteinases, indicating the involvement of transactivation. Exposure to a hypotonic medium caused an immediate (within one min) increase in cell water volume (demonstrated by decrease of fluorescence quenching of calcein), part of which was dependent upon the presence of vasopressin, added at a concentration of 1×10−8M. This vasopressin-dependent component persisted throughout the duration of the experiment (22 min). The effect of vasopressin was abolished in the presence of AG1478, indicating its dependence upon transactivation, and by U0126 an inhibitor of the MAP kinase/ERK kinase (MEK), and thus of ERK1/2phosphorylation.