Aquaporins and CO2 diffusion across biological membrane
Junyu Chen, Ke Yue, Lulu Shen, Chuncui Zheng, Yiyong Zhu, Kun Han, Lei Kai
Abstract
Despite the physiological significance of effective CO 2 diffusion across biological membranes, the underlying mechanism behind this process is not yet resolved. Particularly debatable is the existence of CO 2 -permeable aquaporins. The lipophilic characteristic of CO 2 should, according to Overton’s rule, result in a rapid flux across lipid bilayers. However, experimental evidence of limited membrane permeability poses a challenge to this idea of free diffusion. In this review, we summarized recent progress with regard to CO 2 diffusion, and discussed the physiological effects of altered aquaporin expression, the molecular mechanisms of CO 2 transport via aquaporins, and the function of sterols and other membrane proteins in CO 2 permeability. In addition, we highlight the existing limits in measuring CO 2 permeability and end up with perspectives on resolving such argument either by determining the atomic resolution structure of CO 2 permeable aquaporins or by developing new methods for measuring permeability.