Boric acid transport activity of human aquaporins expressed in Xenopus oocytes

Kazutaka Ushio, Erika Watanabe, Takehiro Kamiya, Ayumi Nagashima, Tadaomi Furuta, Genki Imaizumi, Toru Fujiwara, Michael F. Romero, Akira Kato

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Article numbere15164
JournalPhysiological reports
Issue number1
StatePublished - Jan 2022

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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