Discovery of lipophilic two‐pore channel agonists

Two‐pore channels (TPCs) have been a hot topic in recent literature. Their involvement in various diseases such as viral infections and cancer is of great interest for drug research. Due to their localization in the endolysosomal system and the lack of cell‐permeable activators, complex techniques were required for studying channel functions. Here, we review the first published lipophilic small‐molecule activators of TPCs. In independent high‐throughput screens, several new agonists were discovered, which now allow simple and fast investigation of TPCs in more detail in intact cells and in vivo. Zhang et al. identified tricyclic and phenothiazine antidepressants as TPC1 and TPC2 activators by screening a library of approved drugs. In contrast, Gerndt et al. screened an extensive compound library with mostly new chemotypes and drug structures. The latter resulted in two structurally distinct high‐affinity agonists, which are able to selectively activate TPC2 in either an NAADP‐ or PI(3,5)P2‐like manner. Here, we discuss the advantages and drawbacks of the identified molecules and their structural features. The versatility by which TPCs can be activated indicates many opportunities for future studies. The intracellular two‐pore channels (TPCs), residing on endosomes and lysosomes, are increasingly being implicated in physiology and pathophysiology. The development of TPC activators has lagged behind, for example, the development of TRPML agonists. Recently, two independent papers described the discovery of distinct TPC agonists, for example, the PI(3,5)P2‐mimicking TPC2‐A1‐P (depicted) or voltage‐dependent tricyclic antidepressants. Herein, we review the novel tools developed to study the increasingly relevant two‐pore channels.