Scientists have discovered how sodium influences a group of potassium channels, according to a paper to be published online this week in Nature Chemical Biology. This discovery improves our understanding of ion channels and may offer new insights into the function of known drugs like cardiac glycosides.
Ion channels are proteins that sit in the cell membrane and allow ions such as sodium and chloride to pass from one side of the membrane to the other; this action can cause the buildup of electrical gradients that result in biological processes like the firing of neurons. The activity of inwardly rectifying potassium (Kir) channels is further controlled by a specific lipid in the membrane. Some of the Kir channels are also controlled by sodium, termed 'dual gating', but it was not clear how these two signals would both be needed for channel activity.
Diomedes Logothetis and colleagues used a combined computational-experimental approach to show that sodium prevents the interaction of an aspartate amino acid with an arginine amino acid by binding to the aspartate amino acid. This frees the arginine amino acid to interact with the lipid, which explains how the signals coordinate. This molecular-level insight expands our view of the function of these important channels, represents a potential new avenue for drug design.