Role of EGF receptor activation in angiotensin II-induced renal epithelial cell hypertrophy
Role of EGF receptor activation in angiotensin II-induced renal epithelial cell hypertrophy
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DOI：
10.1681/asn.2005111163
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发表时间：
2006-06-01
影响因子：
13.6
通讯作者：
Harris, Raymond C.
中科院分区：
文献类型：
--
作者：
Chen, Jianchun;Chen, Jian-Kang;Harris, Raymond C.
为了确定血管紧张素II（Ang II）诱导上皮细胞肥大的分子机制，用编码Ang II亚型1受体（AT 1 R/Cl 4）的cDNA转染了一个特征良好的猪肾近端小管细胞系LLCPKc 14，该细胞不表达内源性Ang II受体亚型。Ang Ⅱ可反式激活AT 1 R/Cl 4细胞的EGF受体（EGFR），AT 1 R拮抗剂Losartan可阻断Ang Ⅱ的反式激活，AT 2 R拮抗剂PD 123319则不能阻断Ang Ⅱ的反式激活。Ang II在空载体转染的LLCPKcl 4细胞（Vector/Cl 4）中不反式激活EGFR。血管紧张素II引起释放的可溶性肝素结合EGF样生长因子（HB-EGF）从AT 1 R/Cl 4细胞，和血管紧张素II诱导的EGFR激活被阻止预处理与特定的HB-EGF抑制剂CRM 197或金属蛋白酶抑制剂巴马司他或菲咯啉，没有任何影响EGFR激活外源性EGF。血管紧张素II刺激蛋白质合成和细胞肥大的AT 1 R/Cl 4细胞，而不增加细胞数量，和信号转导研究表明，血管紧张素II刺激磷酸化的40 S核糖体蛋白S6和真核翻译起始因子4 E结合蛋白1，两个下游靶蛋白的哺乳动物靶雷帕霉素，这是一个中央调节蛋白质合成和细胞大小。血管紧张素II诱导的哺乳动物雷帕霉素靶点激活、[H-3]亮氨酸掺入和细胞肥大可通过巴马司他或CRM 197预处理或雷帕霉素或EGFR酪氨酸激酶抑制剂AG 1478预处理来抑制。Ang II还刺激Smad 2/3磷酸化，其被选择性TGF-β受体I激酶抑制剂阻断，但不被CRM 197阻断。通过阻断TGF-β受体，Ang II介导的肥大转化为细胞增殖，这被CRM 197阻断。总之，这是第一次证明HB-EGF脱落依赖性EGFR反式激活，沿着TGF-β信号通路的激活，介导Ang II诱导的肾小管上皮细胞肥大。
For determination of the molecular mechanisms underlying the induction of epithelial cell hypertrophy by angiotensin II (Ang II), a well-characterized porcine renal proximal tubular cell line LLCPKc14, which does not express endogenous Ang II receptor subtypes, was transfected with cDNA encoding Ang II subtype 1 receptor (AT1R/Cl4). Ang II transactivated the EGF receptor (EGFR) in these AT1R/Cl4 cells, which was blocked by the selective AT1R antagonist losartan but not by the selective AT2R antagonist PD123319. Ang II did not transactivate EGFR in empty vector-transfected LLCPKcl4 cells (Vector/Cl4). Ang II elicited release of soluble heparin-binding EGF-like growth factor (HB-EGF) from AT1R/Cl4 cells, and Ang II-induced EGFR activation was prevented by pretreatment with the specific HB-EGF inhibitor CRM197 or the metalloproteinase inhibitors batimastat or phenanthroline, none of which had any effect on EGFR activation by exogenously administered EGF. Ang II stimulated protein synthesis and cell hypertrophy in AT1R/Cl4 cells without increasing cell number, and signaling studies revealed that Ang II stimulated phosphorylation of the 40S ribosomal protein S6 and the eukaryotic translation initiation factor 4E-binding protein 1, the two downstream target proteins of the mammalian target of rapamycin, which is a central regulator of protein synthesis and cell size. Ang II-induced mammalian target of rapamycin activation, [H-3]leucine incorporation, and cellular hypertrophy were inhibited by pretreatment with either batimastat or CRM197 or by pretreatment with rapamycin or the EGFR tyrosine kinase inhibitor AG1478. Ang II also stimulated Smad 2/3 phosphorylation, which was blocked by a selective TGF-beta receptor I kinase inhibitor but not by CRM197. With blockade of TGF-beta receptor, Ang II-mediated hypertrophy was converted into cell proliferation, which was blocked by CRM197. In summary, this is the first demonstration that HB-EGF shedding-dependent EGFR transactivation, along with activation of TGF-beta signaling pathways, mediates Ang II-induced renal tubular epithelial cell hypertrophy.