Boric acid transport activity of human aquaporins expressed in Xenopus oocytes. Issue 1 (10th January 2022)

• Record Type: Journal Article
• Authors: Ushio, Kazutaka; Watanabe, Erika; Kamiya, Takehiro; Nagashima, Ayumi; Furuta, Tadaomi; Imaizumi, Genki; Fujiwara, Toru; Romero, Michael F.; Kato, Akira
• Is Part Of: Physiological reports. Volume 10:Issue 1(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-01-10
• Subjects: aquaglyceroporin -- aquaporin -- boric acid channel -- electrophysiology -- Xenopus oocyte; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.15164
• Languages: English
• ISSNs: 2051-817X

Abstract

Abstract: Boric acid is a vital micronutrient that is toxic at high concentrations in animals. However, the mechanisms underlying boric acid transport in animal cells remain unclear. To identify the plasma membrane boric acid channels in animals, we analyzed the function of human aquaporins (AQPs), which are homologous to the nodulin‐like intrinsic protein family of plant boric acid channels. When human AQPs were expressed in Xenopus laevis oocytes, the results of the swelling assay showed that boric acid permeability significantly increased in oocytes expressing AQP3, 7, 8, 9, and 10, but not in those expressing AQP1, 2, 4, and 5. The boric acid influxes of these oocytes were also confirmed by elemental quantification. Electrophysiological analysis using a pH microelectrode showed that these AQPs transported boric acid (B(OH)3 ) but not borate ions (B(OH)4 – ). These results indicate that AQP3, 7, 8, 9, and 10 act as boric acid transport systems, likely as channels in humans. Abstract : Boric acid transport activities of human aquaporins (AQPs) were analyzed by Xenopus oocyte swelling assay, elemental quantification, and electrophysiological analysis using a pH microelectrode. The results indicate that human AQP3, 7, 8, 9 and 10 act as boric acid channels. This is the first demonstration of identification of boric acid channels in mammals.