Protein phosphatase 1 inhibitor-1 deficiency reduces phosphorylation of renal NaCl cotransporter and causes arterial hypotension.
The thiazide-sensitive NaCl cotransporter (NCC) of the renal distal convoluted tubule (DCT) controls ion homeostasis and arterial BP. Loss-of-function mutations of NCC cause renal salt wasting with arterial hypotension (Gitelman syndrome). Conversely, mutations in the NCC-regulating WNK kinases or kelch-like 3 protein cause familial hyperkalemic hypertension. Here, we performed automated sorting of mouse DCTs and microarray analysis for comprehensive identification of novel DCT-enriched gene products, which may potentially regulate DCT and NCC function. This approach identified protein phosphatase 1 inhibitor-1 (I-1) as a DCT-enriched transcript, and immunohistochemistry revealed I-1 expression in mouse and human DCTs and thick ascending limbs. In heterologous expression systems, coexpression of NCC with I-1 increased thiazide-dependent Na(+) uptake, whereas RNAi-mediated knockdown of endogenous I-1 reduced NCC phosphorylation. Likewise, levels of phosphorylated NCC decreased by approximately 50% in I-1 (I-1(-/-)) knockout mice without changes in total NCC expression. The abundance and phosphorylation of other renal sodium-transporting proteins, including NaPi-IIa, NKCC2, and ENaC, did not change, although the abundance of pendrin increased in these mice. The abundance, phosphorylation, and subcellular localization of SPAK were similar in wild-type (WT) and I-1(-/-) mice. Compared with WT mice, I-1(-/-) mice exhibited significantly lower arterial BP but did not display other metabolic features of NCC dysregulation. Thus, I-1 is a DCT-enriched gene product that controls arterial BP, possibly through regulation of NCC activity.
Institute of Anatomy, University of Zurich, Zurich, Switzerland;
Nicolas
N
Picard
Katja
K
Trompf
Chao-Ling
CL
Yang
R Lance
RL
Miller
Monique
M
Carrel
Dominique
D
Loffing-Cueni
Robert A
RA
Fenton
David H
DH
Ellison
Johannes
J
Loffing
D000818:Animals; D027321:Anion Transport Proteins / Q000378:metabolism; D001794:Blood Pressure; D005260:Female; D006801:Humans; D007022:Hypotension / Q000201:enzymology*; D007686:Kidney Tubules, Distal / Q000201:enzymology*; D008138:Loop of Henle / Q000201:enzymology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D064466:Solute Carrier Family 12, Member 1 / Q000378:metabolism; D064486:Solute Carrier Family 12, Member 3 / Q000378:metabolism*; D000076988:Sulfate Transporters; D015854:Up-Regulation; D014981:Xenopus
D027321:Anion Transport Proteins; D011506:Proteins; C494849:Slc26a4 protein, mouse; D064466:Solute Carrier Family 12, Member 1; D064486:Solute Carrier Family 12, Member 3; D000076988:Sulfate Transporters; C073882:phosphoprotein phosphatase inhibitor 1; C486407:Stk39 protein, mouse; D017346:Protein Serine-Threonine Kinases