Expression of LRRC8/VRAC Currents in Xenopus Oocytes: Advantages and Caveats.

Volume-regulated anion channels (VRACs) play a role in controlling cell volume by opening upon cell swelling. Apart from controlling cell volume, their function is important in many other physiological processes, such as transport of metabolites or drugs, and extracellular signal transduction. VRACs are formed by heteromers of the pannexin homologous protein LRRC8A (also named Swell1) with other LRRC8 members (B, C, D, and E). LRRC8 proteins are difficult to study, since they are expressed in all cells of our body, and the channel stoichiometry can be changed by overexpression, resulting in non-functional heteromers. Two different strategies have been developed to overcome this issue: complementation by transient transfection of LRRC8 genome-edited cell lines, and reconstitution in lipid bilayers. Alternatively, we have used Xenopus oocytes as a simple system to study LRRC8 proteins. Here, we have reviewed all previous experiments that have been performed with VRAC and LRRC8 proteins in Xenopus oocytes. We also discuss future strategies that may be used to perform structure-function analysis of the VRAC in oocytes and other systems, in order to understand its role in controlling multiple physiological functions.