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.jpg): Failed to open stream: No such file or directory in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 117 J+Physiol
2016 ; 594
(17
): 4945-66
Nephropedia Template TP
gab.com Text
Twit Text FOAVip
Twit Text #
English Wikipedia
SPAK and OSR1 play essential roles in potassium homeostasis through actions on
the distal convoluted tubule
#MMPMID27068441
Ferdaus MZ
; Barber KW
; López-Cayuqueo KI
; Terker AS
; Argaiz ER
; Gassaway BM
; Chambrey R
; Gamba G
; Rinehart J
; McCormick JA
J Physiol
2016[Sep]; 594
(17
): 4945-66
PMID27068441
show ga
KEY POINTS: STE20 (Sterile 20)/SPS-1 related proline/alanine-rich kinase (SPAK)
and oxidative stress-response kinase-1 (OSR1) phosphorylate and activate the
renal Na(+) -K(+) -2Cl(-) cotransporter 2 (NKCC2) and Na(+) Cl(-) cotransporter
(NCC). Mouse models suggest that OSR1 mainly activates NKCC2-mediated sodium
transport along the thick ascending limb, while SPAK mainly activates NCC along
the distal convoluted tubule, but the kinases may compensate for each other. We
hypothesized that disruption of both kinases would lead to polyuria and severe
salt-wasting, and generated SPAK/OSR1 double knockout mice to test this. Despite
a lack of SPAK and OSR1, phosphorylated NKCC2 abundance was still high,
suggesting the existence of an alternative activating kinase. Compensatory
changes in SPAK/OSR1-independent phosphorylation sites on both NKCC2 and NCC and
changes in sodium transport along the collecting duct were also observed.
Potassium restriction revealed that SPAK and OSR1 play essential roles in the
emerging model that NCC activation is central to sensing changes in plasma [K(+)
]. ABSTRACT: STE20 (Sterile 20)/SPS-1 related proline/alanine-rich kinase (SPAK)
and oxidative stress-response kinase-1 (OSR1) activate the renal cation
cotransporters Na(+) -K(+) -2Cl(-) cotransporter (NKCC2) and Na(+) -Cl(-)
cotransporter (NCC) via phosphorylation. Knockout mouse models suggest that OSR1
mainly activates NKCC2, while SPAK mainly activates NCC, with possible
cross-compensation. We tested the hypothesis that disrupting both kinases causes
severe polyuria and salt-wasting by generating SPAK/OSR1 double knockout (DKO)
mice. DKO mice displayed lower systolic blood pressure compared with SPAK
knockout (SPAK-KO) mice, but displayed no severe phenotype even after dietary
salt restriction. Phosphorylation of NKCC2 at SPAK/OSR1-dependent sites was lower
than in SPAK-KO mice, but still significantly greater than in wild type mice. In
the renal medulla, there was significant phosphorylation of NKCC2 at
SPAK/OSR1-dependent sites despite a complete absence of SPAK and OSR1, suggesting
the existence of an alternative activating kinase. The distal convoluted tubule
has been proposed to sense plasma [K(+) ], with NCC activation serving as the
primary effector pathway that modulates K(+) secretion, by metering sodium
delivery to the collecting duct. Abundance of phosphorylated NCC (pNCC) is
dramatically lower in SPAK-KO mice than in wild type mice, and the additional
disruption of OSR1 further reduced pNCC. SPAK-KO and kidney-specific OSR1 single
knockout mice maintained plasma [K(+) ] following dietary potassium restriction,
but DKO mice developed severe hypokalaemia. Unlike mice lacking SPAK or OSR1
alone, DKO mice displayed an inability to phosphorylate NCC under these
conditions. These data suggest that SPAK and OSR1 are essential components of the
effector pathway that maintains plasma [K(+) ].