The Importance Of Membrane Channels-- Previously Totally Underestimated By Me

I guess if I had stopped to think about it for a few minutes I would have maybe realized the extreme importance of membrane channels. It's not like I didn't have an awesome biochem course to drive all that stuff home. But if I didn't get it back then, both mammalian physiology and genetics have brought it into stark definition for me this week.

In genetics today we learned that a mutation in a gene called cystic fibrosis trans-membrane conductance regulator (CFTR) is responsible for the disease cystic fibrosis. The mutated gene produces a trans-membrane channel protein that does not allow chloride ions to pass out of the cell. This causes a build-up of chloride ions within the cell (changing the cell membrane's electrochemical gradient) which in turn causes the thick mucus that is characteristic of cystic fibrosis and wreaks havoc on the respiratory system and interferes with the normal function of the GI tract.

I could have told you that preventing chloride ions from exiting the cell as they normally do would have a major impact on an organism, but I wouldn't have predicted it would affect the quality of the mucus (nor do I understand even now exactly why that is the case). Thought provoking stuff. Never underestimate an electrochemical gradient. Electronics (due to the charge on ions), it'll come back to bite you every time.

At the end of the chapter on the electrophysiology of the cell membrane, my mammalian physio book makes reference to Charcot-Marie-Tooth disease, in which a mutated gene causes a defect in the protein connexin 32 that makes up the gap junction between Schwann cell membranes. As a result, the axon is compromised and affected individuals suffer from progressive peripheral nerve degeneration. This example seems more logical, although I'm not sure how a defective gap junction interferes with the myelin insulation around the nerve, which is what my book seems to indicate.

Lots to ponder...