Upregulation of swelling-activated Cl- channel sensitivity to cell volume by activation of EGF receptors in murine mammary cells
Upregulation of swelling-activated Cl- channel sensitivity to cell volume by activation of EGF receptors in murine mammary cells
复制标题
DOI：
10.1113/jphysiol.2003.039784
复制
发表时间：
2003-06-15
影响因子：
5.5
通讯作者：
Okada, Y
中科院分区：
文献类型：
--
作者：
Abdullaev, IF;Sabirov, RZ;Okada, Y
全细胞记录表明，在小鼠乳腺C127细胞转染的牛乳头状瘤病毒（BPV）的全基因组，低渗的挑战诱导激活的外向整流Cl-电流的峰值振幅比对照C127细胞的2.7倍。细胞贴附单通道记录表明，BPV诱导的全细胞电流的峰值振幅的增强不能主要由单位电导的小幅增加（1.2倍）来解释。对照组和BPV转染细胞的渗透性细胞肿胀率没有差异，因此渗透性水渗透性也没有差异。然而，全细胞电流密度作为细胞体积的函数的曲线图，同时测量，显示BPV转染的细胞具有比对照细胞显著更大的体积敏感性。由于已报道BPV的E5蛋白在包括C127细胞在内的多种细胞系中诱导表皮生长因子（EGF）受体和血小板衍生生长因子（PDGF）受体的组成性激活，因此在C127细胞中检查了生长因子对体积敏感性外向整流（VSOR）Cl-电流的影响。应用PDGF肽未能影响对照和BPV转染细胞中的Cl-电流，尽管已知C127细胞内源性表达PDGF受体。与此相反，EGF肽显着增加对照细胞的VSOR Cl-电流。然而，它们未能诱导BPV转染细胞中电流的进一步增强。在对照和BPV转染的细胞中，酪氨酸磷酸化抑制剂B46（EGF受体酪氨酸激酶的抑制剂）抑制VSOR Cl-电流。BPV转染细胞的IC 50值（12 μ m）低于对照细胞（31 μ m）。然而，在这两种细胞类型的VSOR Cl-电流不敏感tyrphostin AG 1296，PDGF受体酪氨酸激酶的抑制剂。酪氨酸磷酸化抑制剂B46可显著降低调节性容积减少率（RVD），但对酪氨酸磷酸化抑制剂AG 1296无显著影响。因此，我们得出结论，EGF受体酪氨酸激酶上调VSOR Cl-通道的活性，主要是通过增强体积敏感性。
Whole-cell recordings showed that, in mouse mammary C127 cells transfected with the full genome of the bovine papilloma virus (BPV), a hypotonic challenge induced the activation of outwardly rectifying Cl- currents with a peak amplitude 2.7 times greater than that in control C127 cells. Cell-attached single-channel recordings showed that BPV-induced augmentation of the peak amplitude of the whole-cell current could not chiefly be explained by a small increase (1.2 times) in unitary conductance. There was no difference between control and BPV-transfected cells in the osmotic cell swelling rate, and hence, osmotic water permeability. However, a plot of the whole-cell current density as a function of cell volume, which was measured simultaneously, showed that the BPV-transfected cells had a strikingly greater volume sensitivity than control cells. Since the E5 protein of BPV has been reported to induce constitutive activation of the epidermal growth factor (EGF) receptor and platelet-derived growth factor (PDGF) receptor in a variety of cell lines including C127 cells, effects of the growth factors on volume-sensitive outwardly rectifying (VSOR) Cl- currents were examined in C127 cells. Application of PDGF peptides failed to affect the Cl- currents in control and BPV-transfected cells, although C127 cells are known to endogenously express PDGF receptors. In contrast, EGF peptides significantly increased the VSOR Cl- current in control cells. However, they failed to induce further augmentation of the current in BPV-transfected cells. VSOR Cl- currents were inhibited by tyrphostin B46, an inhibitor of the EGF receptor tyrosine kinase, in both control and BPV-transfected cells. The IC50 value in BPV-transfected cells (12 mum) was lower than that in control cells (31 mum). However, the VSOR Cl- currents in both cell types were insensitive to tyrphostin AG1296, an inhibitor of the PDGF receptor tyrosine kinase. The rate of regulatory volume decrease (RVD) was markedly diminished by tyrphostin B46 but not significantly affected by tyrphostin AG1296. We thus conclude that the EGF receptor tyrosine kinase upregulates the activity of the VSOR Cl- channel, mainly by enhancing the volume sensitivity.