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Annexin A2 mediates apical trafficking of renal Na(+)-K(+)-2Cl(-)-cotransporter

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Item Type:Article
Title:Annexin A2 mediates apical trafficking of renal Na(+)-K(+)-2Cl(-)-cotransporter
Creators Name:Dathe, C., Daigeler, A.L., Seifert, W., Jankowski, V., Mrowka, R., Kalis, R., Wanker, E., Mutig, K., Bachmann, S. and Paliege, A.
Abstract:The furosemide-sensitive Na(+)-K(+)-2Cl(-)-cotransporter (NKCC2) is responsible for urine concentration, and helps maintain systemic salt homeostasis. Its activity depends on trafficking to, and insertion into, the apical membrane, as well as on phosphorylation of conserved N-terminal serine and threonine residues. Vasopressin (AVP), signaling via PKA and other kinases, activates NKCC2. Association of NKCC2 with lipid rafts facilitates its AVP-induced apical translocation and activation at the surface. Lipid raft microdomains typically serve as platforms for membrane proteins to facilitate their interactions with other proteins, but little is known about partners that interact with NKCC2. Yeast two-hybrid screening identified an interaction between NKCC2 and the cytosolic protein, annexin A2 (AnxA2). Annexins mediate lipid raft-dependent trafficking of transmembrane proteins, including the AVP-regulated water channel, aquaporin 2. Here, we demonstrate that AnxA2, which binds to phospholipids in a Ca(2+)-dependent manner and may organize microdomains, is co-distributed with NKCC2 to promote its apical translocation in response to AVP stimulation and low chloride hypotonic stress. NKCC2 and AnxA2 interact in a phosphorylation-dependent manner. Phosphomimetic AnxA2 carrying a mutant, Src-dependent phosphoacceptor (AnxA2-Y24D-GFP), enhanced surface expression and raft association of NKCC2 by 5-fold upon AVP stimulation, whereas PKC-dependent AnxA2-S26D-GFP did not. As the AnxA2 effect involved only non-phosphorylated NKCC2, it appears to affect NKCC2 trafficking. Overexpression or knockdown experiments further supported the role of AnxA2 in the apical translocation and surface expression of NKCC2. In summary, this study identifies AnxA2 as a lipid raft-associated trafficking factor for NKCC2 and provides mechanistic insight into the regulation of this essential cotransporter.
Keywords:Annexin, Kidney, Phosphorylation, Trafficking, Chloride Channels, Animals, Rats
Source:Journal of Biological Chemistry
Publisher:American Society for Biochemistry and Molecular Biology
Page Range:9983-9997
Date:4 April 2014
Official Publication:https://doi.org/10.1074/jbc.M113.540948
PubMed:View item in PubMed

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