Structural characterization of a Kir potassium channel and its involvement in Andersen’s syndrome

The inward rectifier potassium (Kir) channels belong to a family of integral membrane proteins that selectively control the K+ ion permeation in cell membranes.

They are ubiquitously expressed throughout the human body and regulate the membrane electrical excitability and K+ transport in many cell types.

The gating of Kir channels is modulated by various intracellular ligands, with phosphatidylinositol-4,5-bisphosphate (PIP2) being an essential molecule to Kir channel activity in eukaryotes.

The physiological importance of the Kir channels is highlighted by the fact that genetically-inherited defects in the Kir channels are responsible for a number of human diseases, such as Andersens syndrome (AS), Bartters syndrome, and neonatal diabetes, which are often chronically debilitating and for which there are no efficient therapeutic treatments.

This project goals to obtain high-resolution structures of the human Kir2.1 channel wild type (WT) and an AS-causing mutant (R312H) located at interaction site of PIP2, in the presence and absence of PIP2 as well as the description of the molecular mechanisms allowing gating of the channels in the WT and mutated forms with/without PIP2 using advanced molecular dynamics simulations techniques.

For this, this project proposes the integration of cryo-microscopy (cryo-EM) combined with image analysis (single particle analysis or 2D crystallography) with a recently developed molecular dynamics simulations approach (MDeNM), which is a powerful tool to structurally characterize functional motions occurring over long time scales.

The description of full gating mechanism of human Kir2.1 channel and the PIP2 role on its dynamics, as well as the understanding of the clinically-relevant disease-causing mutation impact on the structure, dynamics, and function of Kir channels can provide the structural basis for investigating potential rationally-designed therapeutic modulators for the AS treatment.