This document, p. 78) In other words, aquaporins regulate the water flux in our skin (specifically in our epidermis, or outer layer of our skin). They are embedded in our cell membranes to help with the transport of water. The one that interests us is listed as aquaglyceroporin-3, or AQP3 for short.
Why do we care about AQP3? Because it's interesting, and because it could be the reason you're suffering from dry skin that doesn't seem to get better no matter how much lotion you apply. "AQP3 is expressed in the basal layer of mammalian skin and is responsible for the epidermal water/glycerol transport. The hydration of SC [stratum corneum], evaluated by high-frequency skin surface conductometry and the estimation of radioactive 3H2O, was reduced in AQP3-deficient mice." (Page 25, this document). What can you do about this dry skin? "Although AQP3 acts as a water channel in the basal keratinocytes, the reduced SC hydration could not be corrected by skin occlusion or exposure to a highly humid environment." (page 25, same document).
Join me tomorrow for more fun with skin chemistry!