Regulator of electrical activity in brain and heart found

Scientists have discovered an outer shield above the entrance of T-type channels that can change the electrochemical signalling of heart and brain cells.

T-type channels can shift from using calcium ions to using sodium ions to generate the electrical signal because of an outer shield of amino acids called a turret, the researchers discovered.

As over-active T-type channels are linked to epilepsy, cardiac problems, neuropathic pain, as well as the spreading of several kinds of cancer, understanding how these shields work could help researchers eventually develop a new class of drugs for treating these diseases.

Low voltage T-type channels generate tiny pulses of current at regular intervals by selectively passing positively charged cations across the membranes of cells through a gate-like channel.

The channels are normally extremely selective, allowing just one sodium ion to pass for every 10,000 calcium ions.

The resulting rhythmic signals produced by this transfer of cations are what support the synchronous contraction of our heart muscles and neuronal firing in parts of the brain, like the thalamus, which helps regulate our sleep-wake cycle, or circadian rhythm.

"We wanted to understand the molecular structures of T-type channels," said David Spafford, a professor at University of Waterloo in Canada.

"How they pass ionic currents to generate electrical activity, and to identify drug binding sites, and the drugs which may block these channels to treat neurological disease or heart complications," added Spafford.

The researchers studied T-type channels in the pond snail lymnaea stagnalis as these channels in pond snails and other invertebrates are similar to those found in humans.

They also found that the shield-like turrets in pond snails restrict access of therapeutic drugs to the channel.

The study appeared in the Journal of Biological Chemistry.