Acid-sensing ion channel proton sensitivity is modulated by a guanidine containing dietary supplement

Acid-sensing ion channels (ASICs) belong to the epithelial/degenerin family. ASICs are sodium selective and are sensitive to extracellular protons specifically those following ischemia and injury. The ASIC1a subtype has been implicated centrally in the neurodegeneration following ischemic stroke while ASIC3 is involved in pain sensation and is expressed peripherally. Protons and inflammatory mediators can activate or modulate ASIC1a and ASIC3, suggesting that ASICs can be a pharmacological target for ischemic stroke and pain. The large extracellular domain of ASICs offers multiple sites for interacting with protons and guanidinium group containing compounds. Guanidinium compounds such as 2-guanidine-4-methylquinazoline (GMQ), amiloride, and agmatine are known to modulate the electrophysiological properties of ASICs. Here we identified a dietary supplement, GL-001 that shares molecular similarity to these ASIC ligands and modulate ASICs. We utilize whole-cell patch-clamp electrophysiology to determine the interaction of GL-001 with endogenous human ASIC1a (hASIC1a) and transiently expressed rat ASIC3 (rASIC3). Our data suggests that GL-001 reduces the hASIC1a pH sensitivity at physiologically relevant supplement concentrations consistent with suggested dietary supplementation. The rASIC3 peak current amplitude and steady-state current is reduced in the presence of GL-001. In the absence of extracellular calcium, GL-001 reduces the rASIC3 proton sensitivity by shifting pH-activation profile to lower pH. This suggests that the effect of GL-001 on rASIC3 is calcium dependent. Future studies will focus on determining the effect of GL-001 on the rASIC3 window current and other ASIC3 properties to resolve the mechanism of action of the GL-001 influence on channel activity.