The Inner Ear Battery and Cx26

So much for weekly updates! In my last blog entry (51 weeks ago) I wrote about how the Connexin 26 protein was used to make Gap Junctions, which in turn allow things to pass between cells. But I wasn't really sure of the role they had in hearing. I thought it might be to do with allowing electrical signals to pass between cells. Turns out I may have been wrong 😲.

I've done a bit more reading in the year since. turns out these so-called experts don't really know. There's a few theories out there though. Some researchers now think that the main role of Cx26 in hearing is to do with the Potassium cycle, and the Inner Ear Battery.

Part of the ear acts like a big battery. The energy from this battery is used to turn small hair vibrations into big electrical pulses that the brain converts to our perception of sound. The charge in the 'ear battery' is carried by Potassium ions. The theory is that without Cx26, the Potassium ions build up in the hair cells, and they die.

Potassium ions are usually referred to as K+. (K is the atomic symbol for Potassium, and the + means it has a positive charge because it is missing an electron). There is a membrane in the ear, one one side you have lots of K+, the other side has less. The K+ wants to get to the side with less. This happens when you hear something, and it causes the Voltage across that membrane to change. This change in voltage drives a signal along the nerve cells to the brain.

The process of how K+ gets across the membrane, and back again, is called the Potassium Cycle. K+ ions pass through the hair cells in the ear and back again. How exactly this happens is uncertain, but some think Gap junctions play a major role, specifically those built using Cx26, and possibly Cx30 as well.

I am not sure exactly why K+ build up causes the hair cells to die, maybe the charge form the ions interferes with other chemical reactions necessary for cell life. I have read that Cx mutations cause inner ear cells to die soon after the onset of hearing (while the fetus is still in the womb), so it doesn't take them long to die.

I'll finish on something cool - scientists have already tapped the 'ear battery' to get an electrical current, which was used to power electronics. Maybe one day they can use this to power hearing aids and cochlear implants. Read about it in the LA times

There you have it - more confused ramblings! If you want more authoritative info on the ear battery, check out this page from Baylor College of medicine. And if you want to know why I'm so confused check out this paper on Gap junctions and the Potassium Cycle