Combining electrical and optical measurements on voltage-gated sodium channel toxins

Ion channels in the membranes of neuronal cells are the key regulators of neuronal signaling. An ion channel works as a gate that can open and close to allow specific molecules to enter or leave the cell. One important type of ion channels are voltage-gated sodium channels (NaVs), which are essential for many processes in our brain. Malfunction of NaVs has been ascribed to a number of diseases, including neuropathic pain and epilepsy. Furthermore, they are key medical targets for local anesthetics and pain medication, as well as the target of dangerous natural toxins.

Although we can target NaVs with drugs, we still don’t fully understand how NaVs work and how certain toxins or drugs open or lock the ion channel gate. The problem is that it is technically challenging to combine techniques probing the function of an ion channel, like electrophysiology, with techniques that provide information about the structure of the channel and the position of toxin binding.

My goal is to understand the mechanism of activation and blocking of ion channels by toxins and drugs. I developed a chip in which I can perform both ultra-high resolution fluorescence microscopy and electrical measurements on single, functional ion channels in a well-controlled environment. This enables me to study both changes in structure and function of ion channels upon toxin or drug binding.

The toxin I am currently interested in is batrachotoxin (BTX), a toxin from poisonous frogs. When BTX binds to NaVs, it keeps the ion channel in the open position. Recently, our collaborators in the Du Bois lab made and modified BTX. They found that small chemical changes of the BTX molecule resulted in changes in its functionality, and even in a change of its function from an activator, keeping the channel open, into a blocker of NaVs.

Using the chip that I developed, I will analyze the binding of BTX and various modified BTX molecules to NaVs, and the effect of BTX binding on the function of the ion channel. A better understanding of the dynamics of NaVs and toxin binding is essential to understand how NaV activity can be influenced. In the future, the chip can also be used to study other ion channels, drugs and toxins. This will not only increase our knowledge of ion channel gating and blocking, but also provide a way forward to design better and more specific drugs.