Department of Physiology and HeartOtago, University of Otago, Dunedin, New Zealand.
Sci Rep. 2019 May 1;9(1):6781. doi: 10.1038/s41598-019-43097-7.
Acid-sensing ion channels (ASICs) belong to the degenerin/epithelial sodium channel protein family that form mechanosensitive ion channels. Evidence as to whether or not ASICs activity is directly modulated by mechanical force is lacking. Human ASICs (hASIC1, hASIC2a and hASIC3a) were heterologously expressed as homomeric channels in Xenopus oocytes and two-electrode voltage-clamp recordings were performed. hASIC3a was expressed in HEK-293 cells and currents measured by whole-cell patch-clamp recordings. ASIC currents in response to shear force (SF) were measured at pH 7.4, acidic pH, or in the presence of non-proton ligands at pH 7.4. SF was applied via a fluid stream generated through a pressurized perfusion system. No effect was observed at pH 7.4. Increased transient currents for each homomeric channel were observed when elevated SF was applied in conjunction with acidic pH (6.0-4.0). The sustained current was not (hASIC2a) or only slightly increased (hASIC1 and hASIC3a). SF-induced effects were not seen in water injected oocytes and were blocked by amiloride. Non-proton ligands activated a persistent current in hASIC1 and cASIC1 (MitTx) and hASIC3a (GMQ) at pH 7.4. Here SF caused a further current increase. Results suggest that ASICs do have an intrinsic ability to respond to mechanical force, supporting their role as mechanosensors in certain local environments.
酸敏离子通道(ASICs)属于机械敏感离子通道的 DEG/ENaC 蛋白家族。目前还缺乏关于 ASICs 活性是否直接受到机械力调节的证据。将人源性 ASICs(hASIC1、hASIC2a 和 hASIC3a)作为同源通道异源表达在非洲爪蟾卵母细胞中,并进行双电极电压钳记录。在 HEK-293 细胞中表达 hASIC3a,并通过全细胞膜片钳记录测量电流。在 pH 7.4、酸性 pH 或在 pH 7.4 时存在非质子配体的情况下测量对切应力(SF)的 ASIC 电流。SF 通过加压灌注系统产生的流体流施加。在 pH 7.4 时没有观察到效果。当升高的 SF 与酸性 pH(6.0-4.0)一起施加时,观察到每个同源通道的瞬态电流增加。持续电流没有增加(hASIC2a)或仅略有增加(hASIC1 和 hASIC3a)。在注入水的卵母细胞中未观察到 SF 诱导的作用,并且被阿米洛利阻断。在 pH 7.4 时,非质子配体激活 hASIC1 和 cASIC1(MitTx)和 hASIC3a(GMQ)中的持续电流。在这里,SF 引起进一步的电流增加。结果表明,ASICs 确实具有对机械力做出反应的内在能力,支持它们在某些局部环境中作为机械感受器的作用。