Tonantzitlolone is a nanomolar potency activator of transient receptor potential canonical 1/4/5 channels

• Published in: British journal of pharmacology 2018-08, Vol.175 (16), p.3361-3368
• Main Authors: Rubaiy, Hussein N, Ludlow, Melanie J, Siems, Karsten, Norman, Katherine, Foster, Richard, Wolf, Dietmar, Beutler, John A, Beech, David J
• Format: Article
• Language: English
• Subjects: Animals; Antineoplastic Agents - pharmacology; Calcium - physiology; Cell Line, Tumor; CHO Cells; Cricetulus; Diterpenes - pharmacology; HEK293 Cells; Humans; Macrocyclic Compounds - pharmacology; Research Paper; Research Papers; TRPC Cation Channels - agonists; TRPC Cation Channels - physiology
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/bph.14379

Background and Purpose The diterpene ester tonantzitlolone (TZL) is a natural product, which displays cytotoxicity towards certain types of cancer cell such as renal cell carcinoma cells. The effect is similar to that of (‐)‐englerin A, and so, although it is chemically distinct, we investigated whether TZL also targets transient receptor potential canonical (TRPC) channels of the 1, 4 and 5 type (TRPC1/4/5 channels). Experimental Approach The effects of TZL on renal cell carcinoma A498 cells natively expressing TRPC1 and TRPC4, modified HEK293 cells overexpressing TRPC4, TRPC5, TRPC4‐TRPC1 or TRPC5‐TRPC1 concatemer, TRPC3 or TRPM2, or CHO cells overexpressing TRPV4 were studied by determining changes in intracellular Ca2+, or whole‐cell or excised membrane patch‐clamp electrophysiology. Key Results TZL induced an elevation of intracellular Ca2+ in A498 cells, similar to that evoked by englerin A. TZL activated overexpressed channels with EC50 values of 123 nM (TRPC4), 83 nM (TRPC5), 140 nM (TRPC4‐TRPC1) and 61 nM (TRPC5‐TRPC1). These effects of TZL were reversible on wash‐out and potently inhibited by the TRPC1/4/5 inhibitor Pico145. TZL activated TRPC5 channels when bath‐applied to excised outside‐out but not inside‐out patches. TZL failed to activate endogenous store‐operated Ca2+ entry or overexpressed TRPC3, TRPV4 or TRPM2 channels in HEK 293 cells. Conclusions and Implications TZL is a novel potent agonist for TRPC1/4/5 channels, which should be useful for testing the functionality of this type of ion channel and understanding how TRPC1/4/5 agonists achieve selective cytotoxicity against certain types of cancer cell.