Minerals Inhibit Aquaporin-mediated Water and CO₂ Gas Transport

抄録

Aquaporin (AQP) water channels facilitate the rapid movement across the plasma membrane throughout animal and plant kingdoms. A plant AQP, NtAQP has also shown to CO₂ gas permeability, enhancing photosynthesis and leaf growth, using NtAQP null tobacco. However, to elucidate the physiological role of AQPs, it would be worthwhile to identify AQP inhibitors. Hg²⁺ is the most popular inhibitor for AQPs so far, and the inhibitory effects of Ag²⁺ on AQP1 and Ni⁺ on AQP3 have been recently reported, suggesting AQPs are sensitive to minerals. We, therefore, studied the effects of various minerals on AQP1-AQP5-mediated water and CO₂ gas transport in Xenopus oocyte expression system. We found new AQP inhibitors, Zn²⁺ as an isoform-nonselective inhibitor, and Mn²⁺ as an AQP4 and AQP5 selective inhibitors. Further, the mineral sensitivity of AQPs-mediated water and CO₂ gas transports were different, showing that AQP transport CO₂ gas by different mechanism from that for water.