Localization and interaction of NHERF isoforms in the renal proximal tubule of the mouse.
In expression systems and in yeast, Na/H exchanger regulatory factor (NHERF)-1 and NHERF-2 have been demonstrated to interact with the renal brush border membrane proteins NHE3 and Npt2. In renal tissue of mice, however, NHERF-1 is required for cAMP regulation of NHE3 and for the apical targeting of Npt2 despite the presence of NHERF-2, suggesting another order of specificity. The present studies examine the subcellular location of NHERF-1 and NHERF-2 and their interactions with target proteins including NHE3, Npt2, and ezrin. The wild-type mouse proximal tubule expresses both NHERF-1 and NHERF-2 in a distinct pattern. NHERF-1 is strongly expressed in microvilli in association with NHE3, Npt2, and ezrin. Although NHERF-2 can be detected weakly in the microvilli, it is expressed predominantly at the base of the microvilli in the vesicle-rich domain. NHERF-2 appears to associate directly with ezrin and NHE3 but not Npt2. NHERF-1 is involved in the apical expression of Npt2 and the presence of other Npt2-binding proteins does not compensate totally for the absence of NHERF-1 in NHERF-1-null mice. Although NHERF-1 links NHE3 to the actin cytoskeleton through ezrin, the absence of NHERF-1 does not result in a generalized disruption of the architecture of the cell. Thus the mistargeting of Npt2 seen in NHERF-1-null mice likely represents a specific disruption of pathways mediated by NHERF-1 to achieve targeting of Npt2. These findings suggest that the organized subcellular distribution of the NHERF isoforms may play a role in the specific interactions mediating physiological control of transporter function.
Wade
James B
JB
Dept. of Physiology, 655 W, Baltimore St., Univ. of Maryland, Baltimore, MD 21201, USA. jwade@umaryland.edu
Liu
Jie
J
Coleman
Richard A
RA
Cunningham
Rochelle
R
Steplock
Deborah A
DA
Lee-Kwon
Whaseon
W
Pallone
Thomas L
TL
Shenolikar
Shirish
S
Weinman
Edward J
EJ
D000818:Animals; D015153:Blotting, Western; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000502:physiology* / Q000648:ultrastructure*; D051379:Mice; D008817:Mice, Mutant Strains; D008854:Microscopy, Electron; D008871:Microvilli / Q000378:metabolism / Q000648:ultrastructure; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011233:Precipitin Tests; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; D027981:Symporters / Q000378:metabolism; D000099149:Ezrin
D003598:Cytoskeletal Proteins; D010750:Phosphoproteins; D020033:Protein Isoforms; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D050608:Sodium-Phosphate Cotransporter Proteins; D050609:Sodium-Phosphate Cotransporter Proteins, Type I; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; D027981:Symporters; D000099149:Ezrin; C493549:Slc17a2 protein, mouse; C000613386:Slc9a3 protein, mouse; C093376:sodium-hydrogen exchanger regulatory factor