Aquaporins in kidney pathophysiology

Noda, Yumi; Sohara, Eisei; Ohta, Eriko; Sasaki, Sei

doi:10.1038/nrneph.2009.231

Cited by 132 publications

(113 citation statements)

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“…This phenotype is clinically relevant, as increasing AQP2 at the apical membrane is the desired therapeutic outcome when treating patients with NDI (8,55). Current treatment options for patients with congenital NDI are limited and relatively ineffective (2). Hence, elucidating the signaling pathways disrupted in AKAP220-KO mice could reveal new pharmacological targets for this disease.…”

Section: Discussionmentioning

confidence: 99%

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AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption

Whiting

Ogier

Forbush

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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Filtration through the kidney eliminates toxins, manages electrolyte balance, and controls water homeostasis. Reabsorption of water from the luminal fluid of the nephron occurs through aquaporin-2 (AQP2) water pores in principal cells that line the kidney-collecting duct. This vital process is impeded by formation of an "actin barrier" that obstructs the passive transit of AQP2 to the plasma membrane. Bidirectional control of AQP2 trafficking is managed by hormones and signaling enzymes. We have discovered that vasopressin-independent facets of this homeostatic mechanism are under the control of A-Kinase Anchoring Protein 220 (AKAP220; product of the Akap11 gene). CRISPR/Cas9 gene editing and imaging approaches show that loss of AKAP220 disrupts apical actin networks in organoid cultures. Similar defects are evident in tissue sections from AKAP220-KO mice. Biochemical analysis of AKAP220-null kidney extracts detected reduced levels of active RhoA GTPase, a well-known modulator of the actin cytoskeleton. Fluorescent imaging of kidney sections from these genetically modified mice revealed that RhoA and AQP2 accumulate at the apical surface of the collecting duct. Consequently, these animals are unable to appropriately dilute urine in response to overhydration. We propose that membrane-proximal signaling complexes constrained by AKAP220 impact the actin barrier dynamics and AQP2 trafficking to ensure water homeostasis. yet only approximately 1.5 L of urine is excreted. The majority of this water is reabsorbed from the luminal fluid of the nephron (1). Regulated water reabsorption in response to dehydration occurs through aquaporin-2 (AQP2) water pores in the principal cells of the collecting duct (2). This is stimulated by the hormone arginine vasopressin (AVP). Vasopressin induces PKA phosphorylation of serine 256 on AQP2 and stimulates its translocation from intracellular vesicles to the apical membranes of cells lining the collecting ducts. Reabsorption of water through the kidney preserves fluid balance and results in more concentrated urine (3, 4). Conversely, when an animal ingests excess water, decreased plasma osmolality inhibits vasopressin release, and AQP2 is recovered from the apical membrane by endocytosis. This renders the collecting duct impermeable to water, thereby diverting excess water through the ureter to the bladder.Not surprisingly, defects in AQP2 trafficking have pathophysiological outcomes. For example, nephrogenic diabetes insipidus (NDI) is associated with impaired vasopressin signaling to AQP2 (5-8). Symptoms include excessive thirst, excretion of a large volume of dilute urine, and electrolyte imbalances, including hypernatremia (1, 5). Hereditary forms of this disease appear in patients with inactivating mutations in the V2 vasopressin receptor (V2R) or AQP2 (9-12). Thus, understanding the molecular mechanisms that govern bidirectional control of AQP2 location may lead to new therapeutic approaches for the treatment of NDI.Although the enzymes and effector proteins that govern AQP2 in...

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Section: Discussionmentioning

confidence: 99%

“…The majority of this water is reabsorbed from the luminal fluid of the nephron (1). Regulated water reabsorption in response to dehydration occurs through aquaporin-2 (AQP2) water pores in the principal cells of the collecting duct (2). This is stimulated by the hormone arginine vasopressin (AVP).…”

mentioning

confidence: 99%

AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption

Whiting

Ogier

Forbush

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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“…Among the 16 symptomatic female subjects, 4 were diagnosed as having complete NDI, and 3 were the probands in each family. The types of mutations identified in these symptomatic carriers were: missense mutations (8), deletion mutations (6), nonsense mutation (1), and insertion mutation (1), indicating that this event occurs in any type of mutation.…”

Section: Frequency Of Symptomatic Carriers Of Avpr2 Mutationsmentioning

confidence: 99%

“…The AQP2 gene is located on chromosome 12 (12q13.12), and NDI caused by AQP2 mutations shows both autosomal recessive and dominant inheritance (OMIM 125800, 107777) [7,8]. Several review papers have claimed that about 90 % of NDI patients carry AVPR2 mutations and about 10 % carry AQP2 mutations; however, actual data in support of this estimate have not been shown [1,3].…”

Section: Introductionmentioning

confidence: 99%

Hereditary nephrogenic diabetes insipidus in Japanese patients: analysis of 78 families and report of 22 new mutations in AVPR2 and AQP2

et al. 2012

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Background Familial form of nephrogenic diabetes insipidus (NDI) is a rare hereditary disease caused by arginine vasopressin type 2 receptor (AVPR2) or water channel aquaporin 2 (AQP2) gene mutations. It is speculated that 90 % of NDI families carry disease-causing mutations in AVPR2 and 10 % carry the mutations in AQP2; however, these percentages have not been supported by actual data. It is also unknown whether these percentages vary in different ethnic groups. Methods Gene mutation analyses were performed for 78 Japanese NDI families. All exons and intron-exon boundaries of the AVPR2 and AQP2 genes were directly sequenced. Results A total of 62 families (79 %) carried diseasecausing mutations in AVPR2, while nine families (12 %) carried mutations in AQP2. We identified 22 novel putatively disease-causing mutations (19 in AVPR2 and 3 in AQP2). Regarding AVPR2, 52 disease-causing mutations were identified. Among them, missense mutations were most common (54 %), followed by deletion mutations. In the 64 women who had monoallelic disease-causing AVPR2 mutations, 16 (25 %) had NDI symptoms, including 4 complete NDI subjects. Regarding AQP2, 9 disease-causing mutations were identified in nine families. Two missense mutations and one deletion mutation showed a recessive inheritance, while one missense mutation and five small deletion mutations in the C-terminus of AQP2 showed a dominant inheritance.Conclusions Most Japanese NDI families carry diseasecausing mutations in AVPR2 and 12 % carry mutations in AQP2. A total of 22 novel putatively disease-causing mutations were identified. The relatively high occurrence of symptomatic carriers of AVPR2 mutations needs attention.

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“…Urine volume depends on the function of many aquaporin water channels (AQPs) located in the apical and basolateral membrane of epithelial cells along renal tubules. To date, at least seven AQPs are expressed in the kidney, four of which (AQP1-4) play a major role in renal water reabsorption (17). AQP1 mediates constitutive water reabsorption in the proximal tubules and thin descending limbs of Henle.…”

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confidence: 99%

Farnesoid X receptor (FXR) gene deficiency impairs urine concentration in mice

Zhang

Huang

Гао

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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The farnesoid X receptor (FXR) is a ligand-activated transcription factor belonging to the nuclear receptor superfamily. FXR is mainly expressed in liver and small intestine, where it plays an important role in bile acid, lipid, and glucose metabolism. The kidney also has a high FXR expression level, with its physiological function unknown. Here we demonstrate that FXR is ubiquitously distributed in renal tubules. FXR agonist treatment significantly lowered urine volume and increased urine osmolality, whereas FXR knockout mice exhibited an impaired urine concentrating ability, which led to a polyuria phenotype. We further found that treatment of C57BL/6 mice with chenodeoxycholic acid, an FXR endogenous ligand, significantly up-regulated renal aquaporin 2 (AQP2) expression, whereas FXR gene deficiency markedly reduced AQP2 expression levels in the kidney. In vitro studies showed that the AQP2 gene promoter contained a putative FXR response element site, which can be bound and activated by FXR, resulting in a significant increase of AQP2 transcription in cultured primary inner medullary collecting duct cells. In conclusion, the present study demonstrates that FXR plays a critical role in the regulation of urine volume, and its activation increases urinary concentrating capacity mainly via up-regulating its target gene AQP2 expression in the collecting ducts.water homeostasis | bile acid receptor T he farnesoid X receptor (FXR) is a member of the nuclear receptor superfamily, with the typical functional domains including the DNA binding domain and the ligand binding domain. Upon binding to its ligands, FXR forms a heterodimer with another nuclear receptor, retinoid X receptor, whereupon the receptor dimer binds to the FXR response element (FXRE) located in the promoter regions of FXR target genes, thereby regulating the transcription of these genes (1-3). The single FXR gene gives rise to two isoforms, designated as FXRα and FXRβ, as a result of alternative use of the promoters (4). In addition, each FXR isoform has two variants (FXRα1/FXRβ1 and FXRα2/ β2), depending on the presence or absence of an insert of four amino acids (MYTG) immediately adjacent to the DNA binding domain in the hinge domain (5). Because FXRβ constitutes a pseudogene in humans and primates, all recent studies focus on FXRα (6).FXR is highly expressed in the liver and intestine, where it functions as an intracellular sensor of bile acids and is required for the negative feedback regulation of bile acid biosynthesis and its enterohepatic cycle (7,8). Most recently FXR has been found to be involved in the regulation of adrenal and vascular function, as well as hepatic glucose and lipid metabolism, which suggests an important role for FXR in many tissues beyond the hepatointestinal system (9-12). Among most tissues tested, the kidney exhibits the highest expression levels (13). However, the role of FXR in the kidney remains largely unknown. It has been previously reported that FXR may negatively regulate sterol regulatory element-binding protei...

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Aquaporins in kidney pathophysiology

Cited by 132 publications

References 125 publications

AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption

AKAP220 manages apical actin networks that coordinate aquaporin-2 location and renal water reabsorption

Hereditary nephrogenic diabetes insipidus in Japanese patients: analysis of 78 families and report of 22 new mutations in AVPR2 and AQP2

Farnesoid X receptor (FXR) gene deficiency impairs urine concentration in mice

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