MAL/VIP17, a new player in the regulation of NKCC2 in the kidney.
The renal-specific Na+-K+-2Cl- cotransporter (NKCC2) is the major salt transport pathway of the apical membrane of the mammalian thick ascending limb of Henle's loop. Here, we analyze the role of the tetraspan protein myelin and lymphocytes-associated protein (MAL)/VIP17 in the regulation of NKCC2. We demonstrated that 1) NKCC2 and MAL/VIP17 colocalize and coimmunoprecipitate in Lilly Laboratories cell porcine kidney cells (LLC-PK1) as well as in rat kidney medullae, 2) a 150-amino acid stretch of NKCC2 C-terminal tail is involved in the interaction with MAL/VIP17, 3) MAL/VIP17 increases the cell surface retention of NKCC2 by attenuating its internalization, and 4) this coincides with an increase in cotransporter phosphorylation. Interestingly, overexpression of MAL/VIP17 in the kidney of transgenic mice results in cysts formation in distal nephron structures consistent with the hypothesis that MAL/VIP17 plays an important role in apical sorting or in maintaining the stability of the apical membrane. The NKCC2 expressed in these mice was highly glycosylated and phosphorylated, suggesting that MAL/VIP17 also is involved in the stabilization of NKCC2 at the apical membrane in vivo. Thus, the involvement of MAL/VIP17 in the activation and surface expression of NKCC2 could play an important role in the regulated absorption of Na+ and Cl- in the kidney.
Carmosino
Monica
M
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06511, USA. carmosino@yale.edu
Rizzo
Federica
F
Procino
Giuseppe
G
Basco
Davide
D
Valenti
Giovanna
G
Forbush
Biff
B
Schaeren-Wiemers
Nicole
N
Caplan
Michael J
MJ
Svelto
Maria
M
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D004705:Endocytosis; D004847:Epithelial Cells / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D018374:LLC-PK1 Cells; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009185:Myelin Proteins / Q000235:genetics / Q000378:metabolism*; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D010766:Phosphorylation; D011485:Protein Binding; D011510:Proteolipids / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D011921:Rats, Inbred WKY; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism*; D064466:Solute Carrier Family 12, Member 1; D013552:Swine
C569026:MAL protein, human; C569027:Mal protein, mouse; C569028:Mal protein, rat; D026901:Membrane Transport Proteins; D009185:Myelin Proteins; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D011510:Proteolipids; C578714:SLC12A1 protein, human; C578715:Slc12a1 protein, mouse; C578716:Slc12a1 protein, rat; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1