A yeast-based phenotypic screen for aquaporin inhibitors.

Aquaporins mediate transport of water or small, uncharged solutes across cellular membranes according to the prevailing osmotic and chemical gradients. Because of their implication in human diseases and pathophysiological states, aquaporins are considered as potential drug targets. Yet, specific aquaporin inhibitors for in vivo studies are not available. Common functional aquaporin assays that monitor biophysical parameters related to volume changes, such as light scattering or fluorescence quenching, are time consuming and require costly equipment. Hence, they are not well geared for screening large numbers of compounds. In this paper, we describe a less demanding phenotypic yeast-based assay on 96-well microplates. The assay uses a methylamine-sensitive yeast strain in which a methylamine-permeable test aquaporin is expressed to rescue proliferation on selection plates. Specific inhibition of the aquaporin directly correlates to reduced cell proliferation.