Maitotoxin Is a Potential Selective Activator of the Endogenous Transient Receptor Potential Canonical Type 1 Channel in Xenopus laevis Oocytes

Abstract

Maitotoxin (MTX) is the most potent marine toxin known to date. It is responsible for a particular human intoxication syndrome called ciguatera fish poisoning (CFP). Several reports indicate that MTX is an activator of non-selective cation channels (NSCC) in different cell types. The molecular identity of these channels is still an unresolved topic, and it has been proposed that the transient receptor potential (TRP) channels are involved in this effect. In Xenopus laevis oocytes, MTX at picomolar (pM) concentrations induces the activation of NSCC with functional and pharmacological properties that resemble the activity of TRP channels. The purpose of this study was to characterize the molecular identity of the TRP channel involved in the MTX response, using the small interference RNA (siRNA) approach and the two-electrode voltage-clamp technique (TEVC). The injection of a specifically designed siRNA to silence the transient receptor potential canonical type 1 (TRPC1) protein expression abolished the MTX response. MTX had no effect on oocytes, even at doses 20-fold higher compared to cells without injection. Total mRNA and protein levels of TRPC1 were notably diminished. The TRPC4 siRNA did not change the MTX effect, even though it was important to note that the protein level was reduced by the silencing of TRPC4. Our results suggest that MTX could be a selective activator of TRPC1 channels in X. laevis oocytes and a useful pharmacological tool for further studies on these TRP channels.

Structure Elucidation and Biological Evaluation of Maitotoxin-3, a Homologue of Gambierone, from Gambierdiscus belizeanus

“…For instance, we and others have previously described that the toxin induces a rapid and sustained rise in the cytosolic calcium concentration in several cellular models, and this effect, in conjunction with the cellular acidification induced by this toxin could led to a rapid cell death [ 22 ]. However the exact cellular target of this toxin is yet unknown and several options including nonselective cation channels [ 8 , 20 ], voltage-gated calcium channels [ 45 ] and TRP channels [ 21 , 33 ] have been investigated. In contrast, ciguatoxins are potent activators of voltage-gated sodium channels and some of the analogs (P-CTX-1B), but not all of them, have a modest effect on the levels of cytosolic calcium.…”

“…The diversity in the chemical structures and biological activities of the molecules involved in CFP could reflect their different mechanisms of action. Thus, while MTX-like activity is associated with a massive calcium influx and rapid cell death [ 20 , 21 , 22 , 23 ], ciguatoxins and gambierone cause voltage-gated sodium channel activation at negative membrane potentials leading to cell depolarization at rest and to the disruption of peripheral and central nerve transmission [ 3 , 19 ]. Finally, gambierol acts mainly by blocking voltage dependent potassium channels [ 24 , 25 ].…”

TRPC channels: Structure, function, regulation and recent advances in small molecular probes

“…In addition, microinjection of ML204 into amygdala of neuropathic pain rats suppressed mechanical hypersensitivity of the injured limb, as well as affective-like pain behavior, in a dose-dependent manner, without obvious side effects (Wei, Sagalajev, Yüzer, Koivisto, & Pertovaara, 2015). Furthermore, ML204 blocked Ca 2+ entry and cytotoxicity induced by maitotoxin in human neuronal stem cells (Boente-Juncal, Vale, Alfonso, & Botana, 2018), although maitotoxin has been reported to evoke non-selective cation currents in mammalian cells and Xenopus oocytes in a manner that depends on the expression of TRPC1, but not TRPC4 (Brereton, Chen, Rychkov, Harland, & Barritt, 2001;Flores et al, 2017).…”

Marine Heterocyclic Compounds That Modulate Intracellular Calcium Signals: Chemistry and Synthesis Approaches

“…Ca 2+ and Na + influx induced by activation of these channels may lead to plasma membrane depolarization, which, in excitable cells, may, in turn, recruit voltage-gated Ca 2+ channels leading to massive Ca 2+ influx in neurons, muscle or endocrine cells. Recent evidence shows that siRNA-mediated silencing of the TRPC1 channel, the first member of the canonical family of channels, abolishes Ca 2+ influx induced by MTX, thus suggesting that MTX targets and activates TRPC1 channels [ 43 ].…”