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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 Am+J+Physiol+Renal+Physiol
2016 ; 311
(5
): F890-F900
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Activation of the metabolic sensor AMP-activated protein kinase inhibits
aquaporin-2 function in kidney principal cells
#MMPMID27534994
Al-Bataineh MM
; Li H
; Ohmi K
; Gong F
; Marciszyn AL
; Naveed S
; Zhu X
; Neumann D
; Wu Q
; Cheng L
; Fenton RA
; Pastor-Soler NM
; Hallows KR
Am J Physiol Renal Physiol
2016[Nov]; 311
(5
): F890-F900
PMID27534994
show ga
Aquaporin-2 (AQP2) is essential to maintain body water homeostasis. AQP2 traffics
from intracellular vesicles to the apical membrane of kidney collecting duct
principal cells in response to vasopressin [arginine vasopressin (AVP)], a
hormone released with low intravascular volume, which causes decreased kidney
perfusion. Decreased kidney perfusion activates AMP-activated kinase (AMPK), a
metabolic sensor that inhibits the activity of several transport proteins. We
hypothesized that AMPK activation also inhibits AQP2 function. These putative
AMPK effects could protect interstitial ionic gradients required for urinary
concentration during metabolic stress when low intravascular volume induces AVP
release. Here we found that short-term AMPK activation by treatment with
5-aminoimidazole-4-carboxamide-1-?-d-ribofuranoside (AICAR; 75 min) in kidney
tissue prevented baseline AQP2 apical accumulation in principal cells, but did
not prevent AQP2 apical accumulation in response to the AVP analog desmopressin
(dDAVP). Prolonged AMPK activation prevented AQP2 cell membrane accumulation in
response to forskolin in mouse collecting duct mpkCCD(c14) cells. Moreover, AMPK
inhibition accelerated hypotonic lysis of Xenopus oocytes expressing AQP2. We
performed phosphorylation assays to elucidate the mechanism by which AMPK
regulates AQP2. Although AMPK weakly phosphorylated immunoprecipitated AQP2 in
vitro, no direct AMPK phosphorylation of the AQP2 COOH-terminus was detected by
mass spectrometry. AMPK promoted Ser-261 phosphorylation and antagonized
dDAVP-dependent phosphorylation of other AQP2 COOH-terminal sites in cells. Our
findings suggest an increasing, time-dependent antagonism of AMPK on AQP2
regulation with AICAR-dependent inhibition of cAMP-dependent apical accumulation
and AVP-dependent phosphorylation of AQP2. This inhibition likely occurs via a
mechanism that does not involve direct AQP2 phosphorylation by AMPK.