| First Author | Klein JD | Year | 2012 |
| Journal | Am J Physiol Renal Physiol | Volume | 302 |
| Issue | 9 | Pages | F1098-103 |
| PubMed ID | 22301620 | Mgi Jnum | J:183420 |
| Mgi Id | MGI:5318647 | Doi | 10.1152/ajprenal.00664.2011 |
| Citation | Klein JD, et al. (2012) Protein kinase C-alpha mediates hypertonicity-stimulated increase in urea transporter phosphorylation in the inner medullary collecting duct. Am J Physiol Renal Physiol 302(9):F1098-103 |
| abstractText | The UT-A1 urea transporter plays a critical role in the production of concentrated urine. Both vasopressin and hypertonicity increase urea permeability in rat terminal inner medullary collecting ducts (IMCD). Each agonist independently increases UT-A1 phosphorylation and apical plasma membrane accumulation. Vasopressin activates PKA and phosphorylates UT-A1 at serines 486 and 499. Hypertonicity stimulates urea permeability through protein kinase C (PKC) and intracellular calcium. To determine whether the hypertonic stimulation of urea permeability results from a PKC-mediated phosphorylation of UT-A1, rat IMCDs were metabolically labeled with [(32)P]. Hypertonicity stimulated UT-A1 phosphorylation, and this increase was blocked by preincubation with a PKC inhibitor. IMCDs were biotinylated to assess plasma membrane UT-A1. Hypertonicity increased biotinylated UT-A1, and this increase was blocked by preincubation with a PKC inhibitor. When PKC was directly activated using a phorbol ester, total UT-A1 phosphorylation increased, but phosphorylation at serine 486 was not increased, indicating that PKC did not phosphorylate UT-A1 at the same residue as PKA. Since PKC-alpha is a calcium-dependent PKC isoform and PKC-alpha knockout mice have a urine-concentrating defect, it suggested that PKC-alpha may mediate the response to hypertonicity. Consistent with this hypothesis, hypertonicity increased phospho-PKC-alpha in rat IMCDs. Finally, PKC-alpha knockout mice were used to determine whether hypertonicity could stimulate UT-A1 phosphorylation in the absence of PKC-alpha. Hypertonicity significantly increased UT-A1 phosphorylation in wild-type mice but not in PKC-alpha knockout mice. We conclude that PKC-alpha mediates the hypertonicity-stimulated increase in UT-A1 phosphorylation in the IMCD. |
