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Molecular mechanism of osmosensing and ENaC gene expression by src kinase.

src 激酶渗透传感和 ENaC 基因表达的分子机制。

基本信息

批准号：
17590191
负责人：
NIISATO Naomi
金额：
$ 2.3万
依托单位：
Kyoto Prefectural University of Medicine
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2005
资助国家：
日本
起止时间：
2005 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-17590191/
关键词：
tyrosine dephophorylation [Cl^-]_c src kinase ENaC PTP hypotonic stress Na^+ reabsorption cytosolic Cl^-浸透圧センサー Src family kinase クロライド Na^+ 再吸収

项目摘要

Epithelial Na^+ transport in the kidney is important for control of blood pressure and extracellular fluid volume and is regulated by plasma osmolality and hormones. We have indicated that chronic extracellular hypotonicity stimulates Na^+ reabsorption through alpha-ENaC mRNA expression in renal epithelial A6 cell. However, the osmosensing mechanism and the stimulatory mechanism of Na^+ reabsorption through ENaC gene expression are not well understood. We have recently indicated that : 1) the hypotonic stress causes a biphasic reduction of cytosolic Cl^- concentration ([Cl^-]_c), and 2) the hypotonic stress modulates tyrosine phosphorylation of src kinase playing a crucial role in signal transduction. Based on these observations, we hypothesized that cytosolic CL^-acts as a signal molecule to regulate src kinase activity in hypotonic stress and that src kinase plays a crucial role for stimulation of Na^+ reabsorption through ENaC gene expression in renal epithelia. To clarify if the cytosolic Cl^-acts as a signal molecule for the hypotonic stress, we studied the effects of ([Cl^-]_c on phosphorylation of src kinase at Tyr416 which is autophosphorylated for enzymatic activation. In the present study, we found that : 1) both activities of PTP and src kinase decrease at lowered ([Cl^-]_c, and 2) the activity of src kinase is larger than that PTP at lowered ([Cl^-]_c. Furthermore, we study if src kinase activation through reduction of ([Cl^-]_c is involved in stimulation of Na^+ reabsorption by chronic hypotonic stress. Pretreatment with PP2 (a src kinase inhibitor) significantly inhibited chronic hypotonicity-stimulated Na^+ reabsorption through suppression of ENaC mRNA expression. Based on these results, we suggest that hypotonic stress stimulates Na^+ reabsorption through induction of ENaC mRNA expression via src kinase activation by a reduction of ([Cl^-]_c in renal epithelial A6 cells.

肾脏上皮细胞的Na~+转运对血压和细胞外液容量的控制非常重要，并受血浆渗透压和激素的调节。我们发现慢性细胞外低张可通过α-ENaC mRNA的表达刺激肾上皮细胞A6细胞对Na+的重吸收。然而，渗透调节机制和通过ENaC基因表达促进Na+重吸收的机制还不是很清楚。我们最近发现：1)低渗应激引起细胞内氯离子浓度([Cl^-]_c)的双相降低；2)低渗应激调节src激酶的酪氨酸磷酸化，在信号转导中起关键作用。基于这些观察，我们推测细胞内的CL^-作为信号分子调节低渗应激下src激酶的活性，src激酶可能通过ENaC基因的表达在促进肾上皮细胞对Na+的重吸收中起关键作用。为了阐明胞浆中的氯离子是否作为低渗应激的信号分子，我们研究了([Cl^-]c)对酪氨酸酶416处src激酶磷酸化的影响，该酪氨酸酶是自动磷酸化的。在本研究中，我们发现：(1)降低([Cl^-]_c)时，PTP和src激酶活性均下降；(2)降低[[Cl^-]_c时，src激酶活性大于PTP。此外，我们还研究了通过降低([Cl^-]_c而激活的src激酶是否参与了慢性低张应激对Na~+的重吸收。PP2(一种src激酶抑制剂)可通过抑制ENaC mRNA的表达而显著抑制慢性低张刺激的Na+重吸收。根据这些结果，我们认为，低渗应激通过降低肾上皮细胞A6细胞的([Cl^-]_c)激活src激酶，诱导ENaC mRNA的表达，从而刺激Na~+重吸收。