Mechanisms of hyperactivity and C-type inactivation in the diabetic-prone TALK1 L114P mutant potassium channel

The gain-of-function TALK1-L114P mutation, associated with maturity-onset of diabetes of the young (MODY), inhibits insulin secretion via suppressing pancreatic β-cell excitability. However, the structural mechanisms underlying this pathological hyperactivity have remained unclear. By combining molecular dynamics (MD) simulations and electrophysiological analysis, we show that the L114P mutation destabilizes a key interaction network and abolishes a critical hydrogen bond connecting L114 to the selectivity filter (SF). This destabilization increases the flexibility of the S1 K+-binding site, promoting K+ occupancy even under low external K⁺ conditions. Consequently, the mutation enhances channel activity and introduces C-type inactivation, a gating property not previously reported in TALK1. Interestingly, heterodimeric channels formed by TALK1 wild-type and L114P subunits exhibit intermediate activity, consistent with the milder diabetic phenotype observed in MODY patients carrying this TALK1-L114P mutation. These findings reveal the molecular basis of L114P-driven TALK1 hyperactivity and highlight S1 site destabilization as a critical mechanism in K2P channel gating. This work also provides a potential structural framework for the development of therapeutic strategies targeting dysfunctional β-cell excitability in MODY.