Novel insights regarding the operational characteristics and teleological purpose of the renal Na+-K+-Cl2 cotransporter (NKCC2s) splice variants.
The absorptive Na(+)-K(+)-Cl(-) cotransporter (NKCC2) is a polytopic protein that forms homooligomeric complexes in the apical membrane of the thick ascending loop of Henle (TAL). It occurs in at least four splice variants (called B, A, F, and AF) that are identical to one another except for a short region in the membrane-associated domain. Although each of these variants exhibits unique functional properties and distributions along the TAL, their teleological purpose and structural organization remain poorly defined. In the current work, we provide additional insight in these regards by showing in mouse that the administration of either furosemide or an H(2)O-rich diet, which are predicted to alter NKCC2 expression in the TAL, exerts differential effects on mRNA levels for the variants, increasing those of A (furosemide) but decreasing those of F and AF (furosemide or H(2)O). Based on a yeast two-hybrid mapping analysis, we also show that the formation of homooligomeric complexes is mediated by two self-interacting domains in the COOH terminus (residues 671 to 816 and 910 to 1098), and that these complexes could probably include more than one type of variant. Taken together, the data reported here suggest that A, F, and AF each play unique roles that are adapted to specific physiological needs, and that the accomplishment of such roles is coordinated through the splicing machinery as well as complex NKCC2-NKCC2 interactions.
Brunet
Geneviève M
GM
Department of Medicine, Faculty of Medicine, Nephrology Group, L'Hôtel-Dieu de Research Center, Laval University, Québec, Canada G1R 2J6.
Gagnon
Edith
E
Simard
Charles F
CF
Daigle
Nikolas D
ND
Caron
Luc
L
Noël
Micheline
M
Lefoll
Marie-Hélène
MH
Bergeron
Marc J
MJ
Isenring
Paul
P
D017398:Alternative Splicing; D000818:Animals; D005455:Fluorescent Antibody Technique; D005665:Furosemide / Q000008:administration & dosage / Q000494:pharmacology; D006801:Humans; D007668:Kidney / Q000378:metabolism*; D008138:Loop of Henle / Q000378:metabolism; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D009865:Oocytes; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000378:metabolism; D012754:Sharks; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D028021:Sodium-Potassium-Chloride Symporters / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D064466:Solute Carrier Family 12, Member 1; D064506:Solute Carrier Family 12, Member 2; D014162:Transfection; D020798:Two-Hybrid System Techniques; D014867:Water / Q000008:administration & dosage; D014982:Xenopus laevis
D020033:Protein Isoforms; D012333:RNA, Messenger; C578714:SLC12A1 protein, human; C578877:SLC12A2 protein, human; C578715:Slc12a1 protein, mouse; C578878:Slc12a2 protein, mouse; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D064466:Solute Carrier Family 12, Member 1; D064506:Solute Carrier Family 12, Member 2; D014867:Water; D005665:Furosemide