Ugarte G, Delgado R, O'Day P M, Farjah F, Cid L P, Vergara C, Bacigalupo J
Department of Biology, Faculty of Sciences, University of Chile, Santiago, Chile.
J Membr Biol. 2005 Oct;207(3):151-60. doi: 10.1007/s00232-005-0810-3.
We report that Drosophila retinal photoreceptors express inwardly rectifying chloride channels that seem to be orthologous to mammalian ClC-2 inward rectifier channels. We measured inwardly rectifying Cl(-) currents in photoreceptor plasma membranes: Hyperpolarization under whole-cell tight-seal voltage clamp induced inward Cl(-) currents; and hyperpolarization of voltage-clamped inside-out patches excised from plasma membrane induced Cl(-) currents that have a unitary channel conductance of approximately 3.7 pS. The channel was inhibited by 1 mM: Zn(2+) and by 1 mM: 9-anthracene, but was insensitive to DIDS. Its anion permeability sequence is Cl(-) = SCN(-)> Br(-)>> I(-), characteristic of ClC-2 channels. Exogenous polyunsaturated fatty acid, linolenic acid, enhanced or activated the inward rectifier Cl(-) currents in both whole-cell and excised patch-clamp recordings. Using RT-PCR, we found expression in Drosophila retina of a ClC-2 gene orthologous to mammalian ClC-2 channels. Antibodies to rat ClC-2 channels labeled Drosophila photoreceptor plasma membranes and synaptic regions. Our results provide evidence that the inward rectification in Drosophila retinal photoreceptors is mediated by ClC-2-like channels in the non-transducing (extra-rhabdomeral) plasma membrane, and that this inward rectification can be modulated by polyunsaturated fatty acid.
我们报告称，果蝇视网膜光感受器表达内向整流氯离子通道，这些通道似乎与哺乳动物的ClC-2内向整流通道是直系同源的。我们测量了光感受器质膜中的内向整流Cl⁻电流：在全细胞紧密封电压钳制下的超极化诱导内向Cl⁻电流；从质膜上切除的电压钳制内向外翻膜片的超极化诱导Cl⁻电流，其单通道电导约为3.7 pS。该通道受到1 mM Zn²⁺和1 mM 9-蒽的抑制，但对DIDS不敏感。其阴离子通透序列为Cl⁻ = SCN⁻> Br⁻>> I⁻，这是ClC-2通道的特征。外源性多不饱和脂肪酸亚麻酸在全细胞和膜片钳记录中均增强或激活了内向整流Cl⁻电流。使用RT-PCR，我们在果蝇视网膜中发现了与哺乳动物ClC-2通道直系同源的ClC-2基因的表达。针对大鼠ClC-2通道的抗体标记了果蝇光感受器质膜和突触区域。我们的结果提供了证据，表明果蝇视网膜光感受器中的内向整流是由非转导（横纹肌外）质膜中的ClC-2样通道介导的，并且这种内向整流可以被多不饱和脂肪酸调节。
