Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1

Shushi Nagamori, Pattama Wiriyasermkul, Meritxell Espino Guarch, Hirohisa Okuyama, Saya Nakagomi, Kenjiro Tadagaki, Yumiko Nishinaka, Susanna Bodoy, Kazuaki Takafuji, Suguru Okuda, Junko Kurokawa, Ryuichi Ohgaki, Virginia Nunes, Manuel Palacín, Yoshikatsu Kanai

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25 Citations (Scopus)

Abstract

Heterodimeric amino acid transporters play crucial roles in epithelial transport, aswell as in cellular nutrition. Among them, the heterodimer of a membrane protein b0,+AT/SLC7A9 and its auxiliary subunit rBAT/SLC3A1 is responsible for cystine reabsorption in renal proximal tubules. The mutations in either subunit cause cystinuria, an inherited amino aciduria with impaired renal reabsorption of cystine and dibasic amino acids. However, an unsolved paradox is that rBAT is highly expressed in the S3 segment, the late proximal tubules, whereas b0,+AT expression is highest in the S1 segment, the early proximal tubules, so that the presence of an unknown partner of rBAT in the S3 segment has been proposed. In this study, by means of coimmunoprecipitation followed by mass spectrometry, we have found that a membrane protein AGT1/SLC7A13 is the second partner of rBAT. AGT1 is localized in the apical membrane of the S3 segment, where it forms a heterodimer with rBAT. Depletion of rBAT in mice eliminates the expression of AGT1 in the renal apical membrane. We have reconstituted the purified AGT1-rBAT heterodimer into proteoliposomes and showed that AGT1 transports cystine, aspartate, and glutamate. In the apical membrane of the S3 segment, AGT1 is suggested to locate itself in close proximity to sodium-dependent acidic amino acid transporter EAAC1 for efficient functional coupling. EAAC1 is proposed to take up aspartate and glutamate released into luminal fluid by AGT1 due to its countertransport so that preventing the urinary loss of aspartate and glutamate. Taken all together, AGT1 is the long-postulated second cystine transporter in the S3 segment of proximal tubules and a possible candidate to be involved in isolated cystinuria.

Original languageEnglish
Pages (from-to)775-780
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume113
Issue number3
DOIs
Publication statusPublished - 19 Jan 2016
Externally publishedYes

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Keywords

  • Amino acid transporter
  • Cystine reabsorption
  • Cystinuria
  • Kidney

ASJC Scopus subject areas

  • General

Cite this

Nagamori, S., Wiriyasermkul, P., Espino Guarch, M., Okuyama, H., Nakagomi, S., Tadagaki, K., Nishinaka, Y., Bodoy, S., Takafuji, K., Okuda, S., Kurokawa, J., Ohgaki, R., Nunes, V., Palacín, M., & Kanai, Y. (2016). Novel cystine transporter in renal proximal tubule identified as a missing partner of cystinuria-related plasma membrane protein rBAT/SLC3A1. Proceedings of the National Academy of Sciences of the United States of America, 113(3), 775-780. https://doi.org/10.1073/pnas.1519959113