N‐(2‐Methoxyphenyl) Benzenesulfonamide, a Novel Agonist of Neuronal G Protein‐Gated Inward Rectifier K+ Channels

Abstract

G protein-gated inward rectifier K+ (GIRK) channels are members of the super-family of proteins known as inward rectifier K+ (Kir) channels and are expressed throughout the peripheral and central nervous systems. Neuronal GIRK channels are the downstream targets of a number of neuromodulators including opioids, somatostatin (SST), dopamine and cannabinoids. Previous studies have demonstrated that the ATP-sensitive K+ channel, another member of the Kir channel family, is regulated by sulfonamide drugs such as tolbutamide and diazoxide. Therefore, to determine if sulfonamides also modulate GIRK channels, we screened a library of arylsulfonamide compounds using a GIRK channel fluorescent assay that utilized pituitary AtT20 cells expressing GIRK channels along with the SST type-2 and 5 receptors. Enhancement of the GIRK channel fluorescent signal by one compound, N-(2-methoxyphenyl) benzenesulfonamide (MPBS), was dependent on the activation of the channel by SST. In order to determine the mechanism for the augmentation in the fluorescent signal, GIRK currents were recorded in the AtT20 cells using the whole-cell patch clamp technique (Figure 1). In control solution, application of a low concentration (0.5 nM) of SST produced little if any activation of the GIRK channel (Figure 1a). As expected, the subsequent addition of a high concentration (100 nM) of SST caused a robust activation of the current. In contrast, application of 0.5 nM SST caused a strong activation of the current in cells pretreated with MPBS (Figure 1b). In conclusion, MPBS represents a novel prototypic SST-dependent agonist of neuronal GIRK channels. Structural analogs of MPBS are currently being tested for GIRK channel potency, selectivity and mechanism of action. Support or Funding InformationSupported by NSF grant CBET-1606882 to KW. Figure 1Open in figure viewerPowerPoint GIRK currents measured in AtT20 cells during stimulation by somatostatin (SST). Currents were recorded during voltage steps applied from a holding potential of −40 mV to −100 mV during stimulation with either 0.5 or 100 nM SST.