Primary cilia of renal epithelial cells express several members of the transient receptor potential (TRP) class of cation-conducting channel, including TRPC1, TRPM3, TRPM4, TRPP2, and TRPV4. Some cases of autosomal dominant polycystic kidney disease (ADPKD) are caused by defects in TRPP2 (also called polycystin-2, PC2, or PKD2). A large-conductance, TRPP2-dependent channel in renal cilia has been well described, but it is not known whether this channel includes any other protein subunits. To study this question, we investigated the pharmacology of the TRPP2-dependent channel through electrical recordings from the cilia of mIMCD-3 cells, a murine cell line of renal epithelial origin. The pharmacology was found to match that of TRPM3 channels. The ciliary TRPP2-dependent channel is known to be activated by depolarization and by increasing cytoplasmic Ca2+. This activation was greatly enhanced by external pregnenolone sulfate, an agonist of TRPM3 channels. Pregnenolone sulfate did not change the single-channel current-voltage relation. The channels were effectively blocked by isosakuranetin, a specific inhibitor of TRPM3 channels. Both pregnenolone sulfate and isosakuranetin were effective at concentrations as low as 1 μM. Knocking out TRPM3 by CRISPR/Cas9 genome editing eliminated the ciliary channel. Thus the channel is both TRPM3-dependent and TRPP2-dependent, suggesting that it may include both types of subunit. Knocking out TRPM3 did not change the level of TRPP2 protein in the cilia, so it is unlikely that the absence of functional ciliary channels results from a failure of trafficking.

中文翻译：

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肾原发性纤毛的TRPP2依赖性通道也需要TRPM3。

肾上皮细胞的初级纤毛表达阳离子传导通道的瞬时受体电位（TRP）类的几个成员，包括TRPC1，TRPM3，TRPM4，TRPP2和TRPV4。常染色体显性遗传性多囊肾病（ADPKD）的某些情况是由TRPP2（也称为多囊蛋白2，PC2或PKD2）缺陷引起的。肾纤毛中的大电导，TRPP2依赖性通道已被很好地描述，但尚不清楚该通道是否包含任何其他蛋白质亚基。为了研究这个问题，我们通过电记录来自肾上皮起源的鼠细胞系mIMCD-3细胞的纤毛，研究了TRPP2依赖性通道的药理作用。发现药理学与TRPM3通道的药理学匹配。已知纤毛TRPP2依赖性通道可通过去极化和增加细胞质Ca2 +来激活。外部孕烯醇酮硫酸盐（TRPM3通道的激动剂）大大增强了这种活化作用。硫酸孕烯醇酮并没有改变单通道电流-电压关系。通道被异异草酸苷（TRPM3通道的特异性抑制剂）有效阻断。硫酸孕烯醇酮和异硫氰酸盐都可在低至1μM的浓度下有效。通过CRISPR / Cas9基因组编辑剔除TRPM3，消除了纤毛通道。因此，该通道既依赖于TRPM3，又依赖于TRPP2，表明它可能包括两种类型的亚基。剔除TRPM3并不会改变纤毛中TRPP2蛋白的水平，