ABSTRACT
The initial event in arsenic toxicity is uptake into cells. We identified two major pathways of As(OH)3 [the solution form of As(III)] uptake: aqualgyceroporin channels and glucose permeases. First, we identified aquaglyceroporins, channels that transport water and uncharged organic solutes such as glycerol and urea, as transporters for As(OH)3 and Sb(OH)3 (Sanders et al., 1997). Aquaglyceroporins are found in nearly every organism (Bhattacharjee et al., 2008). They are responsible for metalloid conduction, not only of arsenic and antimony, but also boron (Takano et al., 2006) and silicon (Ma et al., 2006), which are especially important for plants, and probably germanium (Ma et al., 2002). Second, we showed that glucose permeases from yeast, rat and humans efficiently transport arsenite (Liu et al., 2004, Jiang et al., 2010). A major pathway of arsenic detoxification is extrusion from cells or sequestration in intracellular compartments. Arsenite efflux is best characterized in bacteria and yeast, where two unrelated extrusion systems have been identified, the ArsAB pump and Acr3 permease (Fu et al., 2011). Recently homologues of the bacterial ArsB (Ma et al., 2008) and Acr3 (Indriolo et al.) arsenic efflux proteins have been identified in plants as well.
