Palmer C P, Zhou X L, Lin J, Loukin S H, Kung C, Saimi Y
Laboratory of Molecular Biology, University of Wisconsin, Madison, WI 53706, USA.
Proc Natl Acad Sci U S A. 2001 Jul 3;98(14):7801-5. doi: 10.1073/pnas.141036198. Epub 2001 Jun 26.
The molecular identification of ion channels in internal membranes has made scant progress compared with the study of plasma membrane ion channels. We investigated a prominent voltage-dependent, cation-selective, and calcium-activated vacuolar ion conductance of 320 pS (yeast vacuolar conductance, YVC1) in Saccharomyces cerevisiae. Here we report on a gene, the deduced product of which possesses significant homology to the ion channel of the transient receptor potential (TRP) family. By using a combination of gene deletion and re-expression with direct patch clamping of the yeast vacuolar membrane, we show that this yeast TRP-like gene is necessary for the YVC1 conductance. In physiological conditions, tens of micromolar cytoplasmic Ca(2+) activates the YVC1 current carried by cations including Ca(2+) across the vacuolar membrane. Immunodetection of a tagged YVC1 gene product indicates that YVC1 is primarily localized in the vacuole and not other intracellular membranes. Thus we have identified the YVC1 vacuolar/lysosomal cation-channel gene. This report has implications for the function of TRP channels in other organisms and the possible molecular identification of vacuolar/lysosomal ion channels in other eukaryotes.
与质膜离子通道的研究相比，内膜中离子通道的分子鉴定进展甚微。我们研究了酿酒酵母中一种突出的电压依赖性、阳离子选择性且由钙激活的320 pS的液泡离子电导（酵母液泡电导，YVC1）。在此，我们报道了一个基因，其推导产物与瞬时受体电位（TRP）家族的离子通道具有显著同源性。通过基因缺失与重新表达相结合，并直接对酵母液泡膜进行膜片钳记录，我们表明这个酵母TRP样基因是YVC1电导所必需的。在生理条件下，数十微摩尔的细胞质Ca(2+)可激活包括Ca(2+)在内的阳离子跨液泡膜所携带的YVC1电流。对标记的YVC1基因产物进行免疫检测表明，YVC1主要定位于液泡而非其他细胞内膜。因此，我们鉴定出了YVC1液泡/溶酶体阳离子通道基因。本报告对TRP通道在其他生物体中的功能以及其他真核生物中液泡/溶酶体离子通道的可能分子鉴定具有启示意义。
