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Author Notes:

Correspondence to: Guangping Chen, Ph.D., Department of Physiology, Emory University School of Medicine, Whitehead Research Building Room 615, 615 Michael Street, Atlanta, GA 30322, Tel: 404-727-7494, Fax: 404-727-2648, gchen3@emory.edu, , Xiang Song, MD, Cardiovascular Center, The fourth affiliated hospital, Harbin Medical University, 31 Yinhang Street, Nangang District, Harbin, Heilongjiang 150001, China, song761231@sina.com

Subjects:

Research Funding:

This work was supported by NIH grants R01-DK087838 (to G. Chen), R01-DK89828 (to J. Sands), and by Chinese National Natural Science Foundation Project 81570358, 81300248 (to X. Song), Heilongjiang Science and Technology funding LBH-Q13113 (to X. Song).

Keywords:

  • Science & Technology
  • Life Sciences & Biomedicine
  • Physiology
  • Glycosylation
  • Sialyltransferase
  • Urea transporter
  • Protein kinase C
  • CONCENTRATING DEFECT
  • COLLECTING DUCT
  • MICE LACKING
  • UT-B
  • SIALYLATION
  • PROTEIN
  • GLYCOSYLATION
  • MEMBRANE
  • PHOSPHORYLATION
  • ACCUMULATION

Modulation of kidney urea transporter UT-A3 activity by alpha2,6-sialylation

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Journal Title:

Pflügers Archiv European Journal of Physiology

Volume:

Volume 468, Number 7

Publisher:

, Pages 1161-1170

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Two urea transporters, UT-A1 and UT-A3, are expressed in the kidney terminal inner medullary collecting duct (IMCD) and are important for the production of concentrated urine. UT-A1, as the largest isoform of all UT-A urea transporters, has gained much attention and been extensively studied; however, the role and the regulation of UT-A3 are less explored. In this study, we investigated UT-A3 regulation by glycosylation modification. A site-directed mutagenesis verified a single glycosylation site in UT-A3 at Asn279. Loss of the glycosylation reduced forskolin-stimulated UT-A3 cell membrane expression and urea transport activity. UT-A3 has two glycosylation forms, 45 and 65 kDa. Using sugar-specific binding lectins, the UT-A3 glycosylation profile was examined. The 45-kDa form was pulled down by lectin concanavalin A (Con A) and Galant husnivalis lectin (GNL), indicating an immature glycan with a high amount of mannose (Man), whereas the 65-kDa form is a mature glycan composed of acetylglucosamine (GlcNAc) and poly-N-acetyllactosame (poly-LacNAc) that was pulled down by wheat germ agglutinin (WGA) and tomato lectin, respectively. Interestingly, the mature form of UT-A3 glycan contains significant amounts of sialic acid. We explored the enzymes responsible for directing UT-A3 sialylation. Sialyltransferase ST6GalI, but not ST3GalIV, catabolizes UT-A3 α2,6-sialylation. Activation of protein kinase C (PKC) by PDB treatment promoted UT-A3 glycan sialylation and membrane surface expression. The PKC inhibitor chelerythrine blocks ST6GalI-induced UT-A3 sialylation. Increased sialylation by ST6GalI increased UT-A3 protein stability and urea transport activity. Collectively, our study reveals a novel mechanism of UT-A3 regulation by ST6GalI-mediated sialylation modification that may play an important role in kidney urea reabsorption and the urinary concentrating mechanism.

Copyright information:

© 2016, Springer-Verlag Berlin Heidelberg.

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