(-)-Englerin A-evoked Cytotoxicity Is Mediated by Na+ Influx and Counteracted by Na+/K+-ATPase
Melanie J Ludlow1, Hannah J Gaunt1, Hussein N Rubaiy1
1From the Leeds Institute of Cardiovascular and Metabolic Medicine, School of Medicine, University of Leeds, Leeds LS2 9JT, United Kingdom and.
Abstract:
(-)-Englerin A ((-)-EA) has a rapid and potent cytotoxic effect on several types of cancer cell that is mediated by plasma membrane ion channels containing transient receptor potential canonical 4 (TRPC4) protein. Because these channels are Ca2+-permeable, it was initially thought that the cytotoxicity arose as a consequence of Ca2+ overload. Here we show that this is not the case and that the effect of (-)-EA is mediated by a heteromer of TRPC4 and TRPC1 proteins. Both TRPC4 and TRPC1 were required for (-)-EA cytotoxicity; however, although TRPC4 was necessary for the (-)-EA-evoked Ca2+ elevation, TRPC1 was not. TRPC1 either had no role or was a negative regulator of Ca2+ entry. By contrast, both TRPC4 and TRPC1 were necessary for monovalent cation entry evoked by (-)-EA, and (-)-EA-evoked cell death was dependent upon entry of the monovalent cation Na+ We therefore hypothesized that Na+/K+-ATPase might act protectively by counteracting the Na+ load resulting from sustained Na+ entry. Indeed, inhibition of Na+/K+-ATPase by ouabain potently and strongly increased (-)-EA-evoked cytotoxicity. The data suggest that (-)-EA achieves cancer cell cytotoxicity by inducing sustained Na+ entry through heteromeric TRPC1/TRPC4 channels and that the cytotoxic effect of (-)-EA can be potentiated by Na+/K+-ATPase inhibition.
Insights
(-)-Englerin A ((-)-EA) kills cancer cells by triggering sodium (Na+) entry via TRPC1/TRPC4 channels. Inhibiting Na+/K+-ATPase enhances this potent anti-cancer effect, offering new therapeutic strategies.
Area of Science:
- Molecular Biology
- Cell Biology
- Pharmacology
Background:
- (-)-Englerin A ((-)-EA) exhibits potent cytotoxicity against various cancer cells.
- Initial studies suggested Ca2+ overload via TRPC4 channels mediated this effect.
- The precise ion channel mechanisms and cellular targets of (-)-EA remained unclear.
Purpose of the Study:
- To elucidate the specific ion channels and ion transport mechanisms underlying (-)-EA-induced cancer cell cytotoxicity.
- To investigate the roles of TRPC1 and TRPC4 proteins in (-)-EA's action.
- To explore the potential involvement of Na+/K+-ATPase in regulating (-)-EA's cytotoxic effects.
Main Methods:
- Utilized cell-based assays to assess cytotoxicity and ion flux.
- Employed molecular biology techniques to study TRPC1 and TRPC4 protein expression and function.
- Investigated the effects of TRPC4 and TRPC1 channel activity on Ca2+ and monovalent cation (Na+) entry.
- Examined the impact of Na+/K+-ATPase inhibition on (-)-EA cytotoxicity.
Main Results:
- (-)-EA cytotoxicity is mediated by a heteromeric complex of TRPC4 and TRPC1 channels, not solely TRPC4.
- While TRPC4 is essential for Ca2+ elevation, TRPC1 is not; TRPC1 may negatively regulate Ca2+ entry.
- Both TRPC4 and TRPC1 are crucial for (-)-EA-evoked monovalent cation entry, specifically Na+.
- Inhibition of Na+/K+-ATPase significantly potentiates (-)-EA-induced cancer cell death.
- (-)-EA cytotoxicity is dependent on sustained Na+ influx through TRPC1/TRPC4 heteromers.
Conclusions:
- (-)-EA induces cancer cell death by promoting sustained Na+ entry via TRPC1/TRPC4 heteromeric channels.
- The cytotoxic mechanism does not rely on Ca2+ overload but on Na+ influx.
- Na+/K+-ATPase plays a protective role against (-)-EA's effects, and its inhibition can enhance cytotoxicity.
- Targeting TRPC1/TRPC4 channels and modulating Na+/K+-ATPase activity represent potential therapeutic strategies for cancer treatment.
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