Resin-acid derivatives as potent electrostatic openers of voltage-gated K channels and suppressors of neuronal excitability

Abstract

Voltage-gated ion channels generate cellular excitability, cause diseases when mutated, and act as drug targets in hyperexcitability diseases, such as epilepsy, cardiac arrhythmia and pain. Unfortunately, many patients do not satisfactorily respond to the present-day drugs. We found that the naturally occurring resin acid dehydroabietic acid (DHAA) is a potent opener of a voltage-gated K channel and thereby a potential suppressor of cellular excitability. DHAA acts via a non-traditional mechanism, by electrostatically activating the voltage-sensor domain, rather than directly targeting the ion-conducting pore domain. By systematic iterative modifications of DHAA we synthesized 71 derivatives and found 32 compounds more potent than DHAA. The most potent compound, Compound 77, is 240 times more efficient than DHAA in opening a K channel. This and other potent compounds reduced excitability in dorsal root ganglion neurons, suggesting that resin-acid derivatives can become the first members of a new family of drugs with the potential for treatment of hyperexcitability diseases.

Structural basis of Nav1.7 inhibition by an isoform-selective small-molecule antagonist

“…All clinically used Nav channel inhibitors are functionally selective, where their time-and statedependence of block favors patterns of electrical activity seen in pathological conditions. Our structural studies define the mechanism of action of a new class of compounds (31,38) that possess both functional and molecular selectivity, a phenomenon previously unknown among small-molecule ligands of the Nav channel family (32)(33)(34). Inhibition by the aryl sulfonamides is exquisitely sensitive to channel activation, which derives from the requisite movement of the R4 gating charge into the extracellular cleft of VSD4 to form pivotal contacts with the antagonist's anionic warhead.…”

“…Indeed, we have observed a unique phospholipid-antagonist-VSD4 tripartite interaction that may expand the importance of the lipid bilayer in ion channel biology and pharmacology. Ultimately, we anticipate that our new crystallization strategy will form the basis for drug design efforts aimed at other voltage-gated ion channels (32)(33)(34) and hope that the Nav1.7 structures reported here will accelerate the development of superior treatments for pain. General Medical Sciences.…”

“…Here, we describe the structural basis of Nav1.7 inhibition by this class of small-molecule antagonist using x-ray crystallography, and thus present important experimental structures of a small-molecule gating modifier in complex with a voltage-gated ion channel. Our study reveals the details of how an isoform-selective antagonist binds to VSD4 in a membrane environment to inhibit Nav1.7 (movie 1), and therefore highlights VSDs as untapped potential therapeutic targets (32)(33)(34). To enable these unique mammalian Nav channel crystal structures, we exploited the established portability of VSDs (11,(35)(36)(37) and the presumed structural relatedness between human and bacterial Nav channels (3) to develop a robust protein production and crystallization strategy.…”

Polyunsaturated fatty acids are potent openers of human M‐channels expressed in Xenopus laevis oocytes

“…DRG neurons were dissected and cultured for 1-2 days as previously described (Ottosson et al 2015). Recordings were done at room temperature in whole-cell current-clamp mode.…”

Molecular Mechanisms of Resin Acids and Their Derivatives on the Opening of a Potassium Channel

“…If there is no alteration in slope or amplitude, as sometimes reported for polyunsaturated fatty acids (PUFAs) (Xu et al 2008), the shift can be measured at any level of the G(V) curve, always giving the same results. However, for some compounds and mutated channels the effect cannot be described by a simple shift of the G(V) curve along the voltage axis; there is a combination of an amplitude increase and a shift of the G(V) curve (Ottosson et al 2014, Ottosson et al 2015. The shift of the G(V) curve can either be determined by (i) calculating the difference between V½ in control solution and V½ in test solution, or by (ii) determining the shift at the foot of the curve without a normalization of the curve ).…”