Activation of protein kinase C alpha increases phosphorylation of the UT-A1 urea transporter at serine 494 in the inner medullary collecting duct

作者：Blount Mitsi A^*; Cipriani Penelope; Redd Sara K; Ordas Ronald J; Black Lauren N; Gumina Diane L; Hoban Carol A; Klein Janet D; Sands Jeff M

来源：American Journal of Physiology - Cell Physiology, 2015, 309(9): C608-C615.

DOI：10.1152/ajpcell.00171.2014

• vasopressin
• urea transport
• cAMP
• UT-A1
• PKC

Hypertonicity increases urea transport, as well as the phosphorylation and membrane accumulation of UT-A1, the transporter responsible for urea permeability in the inner medullary collect duct (IMCD). Hypertonicity stimulates urea transport through PKC-mediated phosphorylation. To determine whether PKC phosphorylates UT-A1, eight potential PKC phosphorylation sites were individually replaced with alanine and subsequently transfected into LLC-PK1 cells. Of the single mutants, only ablation of the S494 site dampened induction of total UT-A1 phosphorylation by the PKC activator phorbol dibutyrate (PDBu). This result was confirmed using a newly generated antibody that specifically detected phosphorylation of UT-A1 at S494. Hypertonicity increased UT-A1 phosphorylation at S494. In contrast, activators of cAMP pathways (PKA and Epac) did not increase UT-A1 phosphorylation at S494. Activation of both PKC and PKA pathways increased plasma membrane accumulation of UT-A1, although activation of PKC alone did not do so. However, ablating the PKC site S494 decreased UT-A1 abundance in the plasma membrane. This suggests that the cAMP pathway promotes UT-A1 trafficking to the apical membrane where the PKC pathway can phosphorylate the transporter, resulting in increased UT-A1 retention at the apical membrane. In summary, activation of PKC increases the phosphorylation of UT-A1 at a specific residue, S494. Although there is no cross talk with the cAMP-signaling pathway, phosphorylation of S494 through PKC may enhance vasopressin-stimulated urea permeability by retaining UT-A1 in the plasma membrane.

• 出版日期2015-11-1