Roderick C, Reinach P S, Wang L, Lu L
Division of Molecular Medicine, Harbor-UCLA Medical Center, School of Medicine University of California, Los Angeles, Torrance, CA 90502, USA.
J Membr Biol. 2003 Nov 1;196(1):41-50. doi: 10.1007/s00232-003-0623-1.
We characterized the dependence of the mitogenic response by rabbit corneal epithelial (RCE) cells to serum containing growth factors on K(+) channel activation. Using both cell-attached and nystatin-perforated patch-clamp configurations, a K(+) channel was identified whose current-voltage relationship is linear with a single-channel conductance of 31 pS. Its activity was barely detectable following 24 h serum starvation. Exposure of starved cells to either 10% FBS, 5 ng/ml epidermal growth factor (EGF) or 2 n M endothelin-1 (ET-1) continuously increased its activity within 30 min by 40%, 54% and 29%, respectively. EGF and ET-1 in combination had additive effects on such activity. Application of 100 micro M 4-aminopyridine (4-AP), a K(+) channel blocker, inhibited serum-stimulated K(+) channel activity by 85%. DNA synthesis was markedly stimulated by serum, whereas incubation with either 4-AP (200 micro M) or Ba(2+) (1 m M) suppressed this increase by 51% and 23%, respectively, whereas 5 m M tetra ethyl ammonium (TEA) had no effect. Taken together, growth factor-induced increases in proliferation are dependent on K(+) channel stimulation. As the increases in K(+) channel activity induced by ET-1 and EGF were additive, these mitogens may stimulate K(+) channel activity through different signaling pathways linked to their cognate receptors.
我们研究了兔角膜上皮（RCE）细胞对含生长因子血清的促有丝分裂反应对钾离子通道激活的依赖性。使用细胞贴附式和制霉菌素穿孔膜片钳配置，鉴定出一种钾离子通道，其电流-电压关系呈线性，单通道电导为31 pS。血清饥饿24小时后，其活性几乎检测不到。将饥饿细胞暴露于10%胎牛血清、5 ng/ml表皮生长因子（EGF）或2 nM内皮素-1（ET-1）中，在30分钟内其活性分别持续增加40%、54%和29%。EGF和ET-1联合使用对这种活性有相加作用。应用100 μM 4-氨基吡啶（4-AP），一种钾离子通道阻滞剂，可抑制血清刺激的钾离子通道活性85%。血清显著刺激DNA合成，而用4-AP（200 μM）或钡离子（1 mM）孵育分别抑制这种增加51%和23%，而5 mM四乙铵（TEA）则无作用。综上所述，生长因子诱导的增殖增加依赖于钾离子通道刺激。由于ET-1和EGF诱导的钾离子通道活性增加是相加的，这些有丝分裂原可能通过与其同源受体相关的不同信号通路刺激钾离子通道活性。
