Starkus John G, Poerzgen Peter, Layugan Kristine, Kawabata Kelly Galbraith, Goto Jun-Ichi, Suzuki Sayuri, Myers George, Kelly Michelle, Penner Reinhold, Fleig Andrea, Horgen F David
Laboratory of Cell and Molecular Signaling, Center for Biomedical Research at The Queen's Medical Center , Honolulu, Hawaii 96813, United States.
Laboratory of Marine Biological Chemistry, Department of Natural Sciences, Hawaii Pacific University , Kaneohe, Hawaii 96744, United States.
J Nat Prod. 2017 Oct 27;80(10):2741-2750. doi: 10.1021/acs.jnatprod.7b00515. Epub 2017 Oct 11.
TRPM2 is a Ca-permeable, nonselective cation channel that plays a role in oxidant-induced cell death, insulin secretion, and cytokine release. Few TRPM2 inhibitors have been reported, which hampers the validation of TRPM2 as a drug target. While screening our in-house marine-derived chemical library, we identified scalaradial and 12-deacetylscalaradial as the active components within an extract of an undescribed species of Cacospongia (class Demospongiae, family Thorectidae) that strongly inhibited TRPM2-mediated Ca influx in TRPM2-overexpressing HEK293 cells. In whole-cell patch-clamp experiments, scalaradial (and similarly 12-deacetylscalaradial) inhibited TRPM2-mediated currents in a concentration- and time-dependent manner (∼20 min to full onset; IC 210 nM). Scalaradial inhibited TRPM7 with less potency (IC 760 nM) but failed to inhibit CRAC, TRPM4, and TRPV1 currents in whole-cell patch clamp experiments. Scalaradial's effect on TRPM2 channels was shown to be independent of its well-known ability to inhibit secreted phospholipase A (sPLA) and its reported effects on extracellular signal-regulated kinases (ERK) and Akt pathways. In addition, scalaradial was shown to inhibit endogenous TRPM2 currents in a rat insulinoma cell line (IC 330 nM). Based on its potency and emerging specificity profile, scalaradial is an important addition to the small number of known TRPM2 inhibitors.
瞬时受体电位M型2通道（TRPM2）是一种钙离子通透的非选择性阳离子通道，在氧化应激诱导的细胞死亡、胰岛素分泌及细胞因子释放过程中发挥作用。目前报道的TRPM2抑制剂较少，这妨碍了将TRPM2作为药物靶点进行验证。在筛选我们内部的海洋来源化学文库时，我们从一种未描述的钙质海绵（寻常海绵纲，托雷克海绵科）提取物中鉴定出了司卡勒径向海绵骨针毒素和12-脱乙酰司卡勒径向海绵骨针毒素，它们是强力抑制TRPM2过表达的HEK293细胞中TRPM2介导的钙离子内流的活性成分。在全细胞膜片钳实验中，司卡勒径向海绵骨针毒素（以及类似的12-脱乙酰司卡勒径向海绵骨针毒素）以浓度和时间依赖性方式抑制TRPM2介导的电流（约20分钟达到最大效应；半数抑制浓度[IC]为10 nM）。司卡勒径向海绵骨针毒素对TRPM7的抑制作用较弱（IC为60 nM），但在全细胞膜片钳实验中未能抑制钙释放激活钙通道（CRAC）、TRPM4和瞬时受体电位香草酸亚型1（TRPV1）电流。司卡勒径向海绵骨针毒素对TRPM2通道的作用与其抑制分泌型磷脂酶A2（sPLA2）的已知能力及其对细胞外信号调节激酶（ERK）和蛋白激酶B（Akt）信号通路的报道作用无关。此外，司卡勒径向海绵骨针毒素在大鼠胰岛素瘤细胞系中可抑制内源性TRPM2电流（IC为30 nM）。基于其效力和新出现的特异性特征，司卡勒径向海绵骨针毒素是已知的少数TRPM2抑制剂中的重要补充。
