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Author Notes:

Address for reprint requests and other correspondence: J. D. Klein, Emory Univ. School of Medicine, Renal Div., 1639 Pierce Dr., WMB Rm. 3319B, Atlanta, GA 30322 (e-mail: janet.klein@emory.edu).

Subject:

Research Funding:

This work was supported by the National Institutes of Health Grants R01-DK-41707 and P01-DK-61521.

Keywords:

  • urea transporter
  • phospho-specific
  • IMCD3
  • vasopressin
  • forskolin

Phosphorylation of UT-A1 on serine 486 correlates with membrane accumulation and urea transport activity in both rat IMCDs and cultured cells

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Journal Title:

American Journal of Physiology - Renal Physiology

Volume:

Volume 298, Number 4

Publisher:

, Pages F935-F940

Type of Work:

Article | Post-print: After Peer Review

Abstract:

Vasopressin is the primary hormone regulating urine-concentrating ability. Vasopressin phosphorylates the UT-A1 urea transporter in rat inner medullary collecting ducts (IMCDs). To assess the effect of UT-A1 phosphorylation at S486, we developed a phospho-specific antibody to S486-UT-A1 using an 11 amino acid peptide antigen starting from amino acid 482 that bracketed S486 in roughly the center of the sequence. We also developed two stably transfected mIMCD3 cell lines: one expressing wild-type UT-A1 and one expressing a mutated form of UT-A1, S486A/S499A, that is unresponsive to protein kinase A. Forskolin stimulates urea flux in the wild-type UT-A1-mIMCD3 cells but not in the S486A/S499A-UT-A1-mIMCD3 cells. The phospho-S486-UT-A1 antibody identified UT-A1 protein in the wild-type UT-A1-mIMCD3 cells but not in the S486A/S499A-UT-A1-mIMCD3 cells. In rat IMCDs, forskolin increased the abundance of phospho-S486-UT-A1 (measured using the phospho-S486 antibody) and of total UT-A1 phosphorylation (measured by 32P incorporation). Forskolin also increased the plasma membrane accumulation of phospho-S486-UT-A1 in rat IMCD suspensions, as measured by biotinylation. In rats treated with vasopressin in vivo, the majority of the phospho-S486-UT-A1 appears in the apical plasma membrane. In summary, we developed stably transfected mIMCD3 cell lines expressing UT-A1 and an S486-UT-A1 phospho-specific antibody. We confirmed that vasopressin increases UT-A1 accumulation in the apical plasma membrane and showed that vasopressin phosphorylates UT-A1 at S486 in rat IMCDs and that the S486-phospho-UT-A1 form is primarily detected in the apical plasma membrane.

Copyright information:

© 2010 the American Physiological Society

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