1.A.8.9.14
Glycerolaquaporin 9, Aqp9 of 295 aas and 6 TMSs.  Transports water, glycerol and arsenic trioxide, As₂O₃ (Palmgren et al. 2017) as well as urea and lactic acid (but not lactate) (Geistlinger et al. 2022). Primary APL cells express AQP9 significantly (2-3 logs) higher than other acute myeloid leukemia cells (AMLs), explaining their exquisite As₂O₃ sensitivity (Leung et al. 2007). AQP-7 and AQP-9-mediated glycerol transport in tanycyte cells may be under hormonal control to use glycerol as an energy source during the mouse estrus cycle (Yaba et al. 2017). It transports multiple neutral and ionic arsenic species including arsenic trioxide, monomethylarsenous acid (MAs(III)) and dimethylarsenic acid (DMA(V)). It also transports clinically relevant selenium species including monomethylselenic acid (MSeA), especially at acidic pH. FCCP, valinomycin and nigericin do not significantly inhibit MSeA uptake, but AQP9 also transport ionic selenite and lactate, with low efficiency compared with MSeA uptake. Selenite and lactate uptake is pH dependent and inhibited by FCCP and nigericin but not valinomycin. The selenite and lactate uptake via AQP9 can be inhibited by different lactate analogs. AQP9 transport of MSeA, selenite and lactate is inhibited by an AQP9 inhibitor, phloretin, and the AQP9 substrate, arsenite (As(III)) (Geng et al. 2017). The host aquaporin-9 is required for efficient Plasmodium falciparum sporozoite entry into human hepatocytes (Amanzougaghene et al. 2021). RG100204 is a direct blocker of the AQP9 channel (Florio et al. 2022).