HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Supplemental Figures All Versions of this Article: 296/4/C900    most recent 00526.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Riquier, A. D. M. Articles by McDonough, A. A. Search for Related Content PubMed PubMed Citation Articles by Riquier, A. D. M. Articles by McDonough, A. A.

MEMBRANE TRANSPORTERS, ION CHANNELS, AND PUMPS

Renal NHE3 and NaPi2 partition into distinct membrane domains

Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California

Submitted 15 October 2008 ; accepted in final form 16 January 2009

Hypertension provokes differential trafficking of the renal proximal tubule Na⁺/H⁺ exchanger 3 (NHE3) to the base of the apical microvilli and Na⁺-P_i cotransporter 2 (NaPi2) to endosomes. The resultant diuresis and natriuresis are key to blood pressure control. We tested the hypothesis that this differential trafficking of NHE3 vs. NaPi2 was associated with partitioning to distinct membrane domains. In anesthetized rats, arterial pressure was increased (104 ± 2 to 142 ± 4 mmHg, 15 min) by arterial constriction and urine output increased 23-fold. Renal membranes were fractionated by cold 1% Triton X-100 extraction then centrifugation through OptiPrep flotation gradients. In controls, 84 ± 9% of NHE3 localized to flotillin-enriched lipid raft domains and 69 ± 5% of NaPi2 localized to transferrin receptor-enriched nonrafts. MyosinVI and dipeptidyl peptidase IV, associated with NHE3 regulation, coenriched in lipid rafts with NHE3, while NHE regulatory factor-1 coenriched in nonrafts with NaPi2. Partitioning was not altered by hypertension. Detergent insoluble membranes were pelleted after detergent extraction. NHE3 detergent insolubility decreased as it redistributed from body (80 ± 10% detergent insoluble) to base (75 ± 3%) of the apical microvilli, while NaPi2 partitioned into more insoluble domains as it moved from the microvilli (45 ± 7% detergent insoluble) to endosomes (82 ± 1%). In conclusion, NHE3 and NaPi2, while both localized to apical microvilli, are segregated into domains: NHE3 to lipid rafts and NaPi2 to nonrafts. These domain properties may play a role in the distinct trafficking patterns observed during elevated pressures: NHE3 remains in rafts and settles to the base of the microvilli while NaPi2 is freely endocytosed.

subcellular fractionation; hypertension; lipid raft; kidney; proximal tubule