Inhibition mechanism of pancreatic KATP channels by centipede toxins

Abstract

The pancreatic ATP-sensitive potassium (KATP) channel acts as a crucial metabolic sensor by regulating insulin secretion to maintain whole-body energy homeostasis. Gain-of-functional mutations in this channel lead to neonatal diabetes mellitus, a rare disorder in which certain mutants demonstrate resistance to standard sulfonylurea therapy. Recent studies have identified a centipede toxin, SpTx1, as a potent inhibitor of both human pancreatic KATP channels and their gain-of-functional mutants. This toxin stimulates insulin secretion, offering a promising therapeutic strategy for neonatal diabetes. Nevertheless, the molecular mechanism by which SpTx1 inhibits the KATP channel has remained elusive. Here, we report the crystal structure of SpTx1 and the cryo-electron microscopy (cryo-EM) structure of the KATP channel in complex with SpTx1. Our results demonstrate that SpTx1 binds to the extracellular surface of the Kir6.2 pore-forming subunit of the KATP channel. Multiple interactions at the SpTx1-Kir6.2 interface underpin the high affinity and specificity of SpTx1 for human Kir6.2. We show that SpTx1 inhibits potassium currents by physically blocking the ion conduction pore. Furthermore, a structure-guided search identified another centipede toxin, Sm3a, as a novel KATP channel blocker. Together, these findings provide key insights into the inhibitory mechanism of centipede toxins against the human Kir6.2-containing KATP channel and establish a foundation for developing these toxins into potential therapeutics targeting KATP channel-related diseases.