Cantú syndrome is a rare condition that is characterized by coarse facial appearance, hypertrichosis, and multiple cardiovascular abnormalities. The syndrome is associated with gain-of-function mutations to ATP-sensitive potassium channels that disrupt the channel’s normal metabolic feedback control.
In a recent study, published in Journal of Biological Chemistry, researchers at Washington University in St. Louis investigated the H60Y mutation to SUR2 subunit, the part of ATP-sensitive potassium channels that is responsible for regulating channel function. This specific mutation represents a long-standing discrepancy in which the ion channel variant appears functionally benign in conventional assays despite patients carrying this mutation presenting typical Cantú syndrome phenotypes.
To resolve this discrepancy the group of researchers, led by Colin G. Nichols, investigated the effect of pairing the H60Y variant of the SUR2 subunit with either of the two channel-forming subunits Kir6.1 and Kir6.2. Using a patch-clamp assay based on intact cells under physiologically relevant conditions, the researchers were able to show that the mutation indeed causes a gain-of-function, as would be expected for clinical data, but only in channels where SUR2 is paired with Kir6.1 and not when paired with Kir6.2.
In their patch-clamp recordings of potassium channel activities, the researchers used Dynaflow Resolve to achieve rapid and reproducible solution exchange during inside-out patch-clamp recordings, particularly when applying varying concentrations ATP.
To more precisely identify the effect-causing regions of the channels, the researchers created chimeric versions of Kir6.1 and Kir6.2. These experiments revealed that the N-terminus, together with a single valine residue, are the parts of Kir6.1 that are involved in generating the observed gain-of-function effect. The authors write that neither the N-terminus of Kir6.1, nor the single valine residue, are close enough to the mutated histidine in SUR2 to imply a direct physical interaction between these regions. Instead, the authors suggest that channel the observed gain-of-function is caused by an allosteric effect that affects nucleotide sensitivity.
Nichols and colleagues conclude that the gain-of-function caused by the SUR2 H60Y mutation in channels containing the Kir6.1 subunit is consistent with clinical observations in patients carrying this specific mutation, and that their results therefore provide a causal link between this mutation and the disease phenotype. Moreover, the authors hypothesize that the results suggest that Cantú syndrome phenotypes not observed in patients with the H60Y mutations result from Kir6.2/SUR2 gain-of-function.
We congratulate Nichols and colleagues on their achievement and are proud that they have chosen to use Dynaflow Resolve in their research.
Read the paper Cantu syndrome–associated SUR2[H60Y] mutation confers selective gain of function on Kir6.1 ATP-sensitive potassium channels on the Journal of Biological Chemistry website.