Ko Juyeon, Myeong Jongyun, Yang Dongki, So Insuk
Department of Physiology, Seoul National University College of Medicine, Seoul 03080, Korea.
Department of Physiology, College of Medicine, Gachon University, Incheon 21936, Korea.
Korean J Physiol Pharmacol. 2017 Jan;21(1):133-140. doi: 10.4196/kjpp.2017.21.1.133. Epub 2016 Dec 21.
Conflicting evidence has been obtained regarding whether transient receptor potential cation channels (TRPC) are store-operated channels (SOCs) or receptor-operated channels (ROCs). Moreover, the Ca/Na permeability ratio differs depending on whether the current-voltage (I-V) curve has a doubly rectifying shape or inward rectifying shape. To investigate the calcium permeability of TRPC4 channels, we attached GCaMP6s to TRPC4 and simultaneously measured the current and calcium signals. A TRPC4 specific activator, (-)-englerin A, induced both current and calcium fluorescence with the similar time course. Muscarinic receptor stimulator, carbachol, also induced both current and calcium fluorescence with the similar time course. By forming heteromers with TRPC4, TRPC1 significantly reduced the inward current with outward rectifying I-V curve, which also caused the decrease of calcium fluorescence intensity. These results suggest that GCaMP6s attached to TRPC4 can detect slight calcium changes near TRPC4 channels. Consequently, TRPC4-GCaMP6s can be a useful tool for testing the calcium permeability of TRPC4 channels.
关于瞬时受体电位阳离子通道（TRPC）是储存操纵性通道（SOC）还是受体操纵性通道（ROC），已经获得了相互矛盾的证据。此外，钙/钠渗透比取决于电流-电压（I-V）曲线是具有双整流形状还是内向整流形状。为了研究TRPC4通道的钙渗透性，我们将GCaMP6s连接到TRPC4上，并同时测量电流和钙信号。TRPC4特异性激活剂（-）-恩格勒菌素A以相似的时间进程诱导电流和钙荧光。毒蕈碱受体刺激剂卡巴胆碱也以相似的时间进程诱导电流和钙荧光。通过与TRPC4形成异源二聚体，TRPC1显著降低了具有外向整流I-V曲线的内向电流，这也导致钙荧光强度降低。这些结果表明，连接到TRPC4上的GCaMP6s可以检测TRPC4通道附近的轻微钙变化。因此，TRPC4-GCaMP6s可以成为测试TRPC4通道钙渗透性的有用工具。
