Feeling the heat: TRPV1, receptor for hot, capsaicin, and also salt and ethanol!

You probably know about sensitivity to the bitterness of PTC (phenylthiocarbamide) and PROP (6-n-propylthiouracil), and how your sensitivity is genetically programmed. You may even have tried the paper coated with PTC in class in middle or high school. 

Other taste sensitivities are genetically determined as well. As someone who is very sensitive to the burn of chili peppers, I was interested in the genetics of TRPV1, the receptor that causes the burn sensation.

This sensation is created by the binding of the capsaicin in chili peppers to TRPV1, the "hot" receptor. This receptor is designed to respond to temperatures in excess of about 100ºF (40ºC). TRPV1 has numerous genetic variants, which lead to greater or lesser sensitivity, not just to capsaicin, but also to a number of other food components. Here are two examples:

Salt: while a very different receptor in taste buds responds to low salt concentrations, TRPV1 responds to high concentrations with a slight to not-so-slight burning feeling — that's why salt goes so well with caramel. Both caramel and salt at high concentration activates TRPV1, and thereby turns up the volume on caramel flavor perception.

If salt at higher concentrations starts to burn for you it is probably because you have a gain-of-function mutation in your TRPV1 gene that increases salt's ability to activate TRPV1. The original form of the gene leads to moderate sensitivity, while the mutated form leads to greater sensitivity to salt. If you inherit this mutated form from each of your parents, as I did, you are really really sensitive to the "burn" of salt!*

A "burning" heart for Valentine's Day!

Ethanol: Does ethanol (alcohol) burn as it goes down your throat? This burn, too, is due to activation of TRPV1.  Some people experience more of the burn than others, again due to mutations in TRPV1.** In at least one case, the mutation is gain-of-function. This one is a rare mutation, different from the salt burn mutation. I happen to have inherited this mutation from both my parents as well, one of the many reasons I don't tolerate a cabernet sauvignon at 16% alcohol, or even one at 14% alcohol...


* Dias AG, Rousseau D, Duizer L, Cockburn M, Chiu W, Nielsen D, El-Sohemy A. Genetic variation in putative salt taste receptors and salt taste perception in humans. Chem Senses. 2013 Feb;38(2):137-45. doi: 10.1093/chemse/bjs090. Epub 2012 Nov 1.

** Allen AL, McGeary JE, Hayes JE. Polymorphisms in TRPV1 and TAS2Rs associate with sensations from sampled ethanol. Alcohol Clin Exp Res. 2014 Oct;38(10):2550-60. doi: 10.1111/acer.12527. Epub 2014 Sep 25.