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AQP2 (aquaporin 2)

Written2019-03Jean Loup Huret

Abstract Review on aquaporin-2 (AQP2), with data on DNA, on the protein encoded, and where the gene is implicated.

Keywords Aquaporin-2; AQP2; Tissue water balance; Cell migration; Cellular volume regulation; Cell membrane; Channel; Nephrogenic diabetes insipidus; Urine concentration; Collecting duct; Kidney

(Note : for Links provided by Atlas : click)


Alias_namesaquaporin 2 (collecting duct)
Other aliasAQP-CD
HGNC (Hugo) AQP2
LocusID (NCBI) 359
Atlas_Id 52230
Location 12q13  [Link to chromosome band 12q13]
Location_base_pair Starts at 49950741 and ends at 49958881 bp from pter ( according to hg19-Feb_2009)  [Mapping AQP2.png]
Fusion genes
(updated 2017)
Data from Atlas, Mitelman, Cosmic Fusion, Fusion Cancer, TCGA fusion databases with official HUGO symbols (see references in chromosomal bands)


Transcription There are various splicing forms. Canonical form transcript (hg38), including UTRs: chr12:30,911,694 - 30,925,516, size: 13,823bp on forward (+) strand; coding region: chr12: 49,950,746-49,958,881 size: 8,136bp, according to UCSC. Four exons: exon1 (nt 1 - 450) codes for amino acids (aa) 1-120, exon2 (nt 3415 - 3579) for aa 121-175; exon3 (nt 3890 - 3970) for aa 176-202, and exon4 (nt 4659 - 8141) for aa 203-271 (nextProt).


Note Aquaporins are a family of hydrophobic transmembrane channel proteins involved in transport of water and small molecules in response to osmotic gradients. They are distributed throughout many tissues, with various known roles of production, secretion, reabsorption and regulation of water, but also of cell migration (angiogenesis), signal transduction, and cell proliferation. There are 14 AQPs in humans (and 5 pseudogenes): MIP (previously called AQP0), AQP1, AQP2, AQP3, AQP4, AQP5, AQP6, AQP7, AQP8, AQP9, AQP10, AQP11, AQP12Aand AQP12B. They are classified into two families: orthodox aquaporins, that transport water only, and aquaglyceroporins (AQP3, AQP7 and AQP9), which also transport glycerol, urea and other small molecules. AQPs form homo-tetramers (Review in Papadopoulos and Saadoun, 2015). The monomeric units of AQPs are ~30 kDa proteins and consist of 6 transmembrane α-helices (M1, M2, M4 to M6 and M8), 2 intramembrane half helices (M3 and M7), and 5 connecting loops (loops A to E) (Review in Verkman et al., 2014). They bear conserved intramembrane Asn-Pro-Ala (NPA) sequence motifs in the intramembrane domains, and six tilted transmembrane helices per monomer, with linkers (loops A to E). The NPA motifs act as hydrogen-bond donors and acceptors that coordinate the transport of water through the pore (Verkman et al., 2014).
  Figure 1. Aquaporin-2 (AQP2) gene exons and protein domains.
Description Aquaporin-2 canonical form: 271 aa; 28.837kDa; other isoforms; 223, and 244 aa. AQP2 is a transmembrane protein, with a N-term and a C-term cytoplasmic domains: amino acids 1 - 16 (Cytoplasmic), 17 - 34 (Transmembrane), 35 - 40 (Extracellular ("Loop A")), 41 - 59 (Transmembrane), 60 - 85 (Cytoplasmic ("Loop B")), 86 - 107 (Transmembrane), 108 - 127 (Extracellular ("Loop C")), 128 - 148 (Transmembrane), 149 - 156 (Cytoplasmic ("Loop D")), 157 - 176 (Transmembrane), 177 - 202 (Extracellular ("Loop E")), 203 - 224 (Transmembrane), 225 - 271 (Cytoplasmic) (Figure. 1).

Helical subunits in Loop B and E juxtapose to form a water pore in the monomere. The central pore of the homotetramer (Figure. 2) would be a path for ion and gas (Review in Huber et al., 2012). Remarkable sites: (Figure. 1)
NPA: aa 68-70, 184-186
N-myristoylation sites (role in membrane targeting): aa 27-32, 29-34, 49-54, 78-83, 96-101, 128-133, 175-180, 211-216.
N-glycosylation sites: aa 123-126.
Protein kinase C phosphorylation sites: aa 195-197, 231-233 (Thr 195 and Ser 231); Casein kinase II phosphorylation site: aa 108-111 (Thr 108), 148-151 (Ser 148), 229-232 (Ser 229), 244-247 (Thr 244); cAMP-and cGMP-dependent protein kinase (PKA) phosphorylation site :aa 253-256.
Cell attachment sequence RGD (plays a role in cell adhesion): aa 113-115.
Microbodies C-terminal targeting signal (targeting to organelles such as peroxisomes): aa 269-271.
  Figure 2. Aquaporins monomere and tetramere. Aquaporins are transmembrane proteins involved in transport of water and small molecules in response to osmotic gradients (water channels).
Expression AQPs are widely expressed. AQP2 is mainly expressed in the kidney. Renal collecting duct principal cells
Extra-renal localizations: Ear, epididymis, vas deferens, vagina. Both AQP1 and AQP2 are expressed in the endometrium. AQP2 endometrial expression is menstrual cycle-dependent (high at the proliferative and midsecretory phases).
  Figure 3. ModBase predicted comparative 3D structure.
Localisation AQP2 undergoes a constitutive recycling: its trafficking from intracellular vesicles into the plasma membrane and endocytic retrieval to its intracellular storage site. AQP2 forms homotetramers in the endoplasmic reticulum, passes through the Golgi apparatus and is stored in intracellular vesicles in the perinuclear region. Under resting conditions, AQP2 binds monomeric G-actin (ACTG1). F-actin destabilization facilitates translocation of AQP2 to the apical plasma membrane and water reabsorption (Vukićević et al., 2016).
Function AQPs main's role is to maintain tissue water balance. AQPs also facilitate cell migration, cell proliferation and cell adhesion. Cell migration: AQPs concentrate at the leading end of migrating cells and facilitate the formation of the lamellipodium (Papadopoulos and Saadoun, 2015). Cell proliferation: AQPs may activate transduction pathways such as the mitogen-activated protein kinase pathways or the Wnt/beta-catenin ( CTNNB1) signaling.
AQP2 key physiological role is water reabsorption in collecting duct of the kidney to concentrate urine.
Vasopressin / vasopressin receptor / aquaporin-2 axis
In the kidney, AVP 46535 (vasopressin) binds to AVPR2 732 (type 2 vasopressin receptor (V2R)) located in the basolateral membrane of the principal cells of the collecting ducts and increases osmotic water transport through the regulation of the aquaporin-2 water channel localized in the kidney connecting tubules and collecting ducts. Upon binding of vasopressin to AVPR2, the cAMP/PKA (PRKAR1A 387) signal is activated, PRKAR1A is recruited to the vesicles through PRKAR1A-anchoring proteins (AKAPs) (AKAP7 46846 co-localizes with AQP2) and results in phosphorylation in the C-terminus of AQP2 at serines 256, 264, and 269, withdrawing it from F-actin. AQP2 is subsequently translocated to the apical plasma membrane, and the water luminal permeability to increase water reabsorption from urine. Vasopressin also triggers increases in intracellular calcium required for AQP2 trafficking (Reviews in Jung and Kwon 2016; Ando and Uchida 2018; De Ieso and Yool 2018; Ranieri et al., 2019).
However, cAMP-independent mechanisms for AQP2 trafficking also exist.
Nuclear receptors, especially PPARG (Peroxisome proliferator-activated receptor gamma), NR1H2 (LXRB, Liver X receptor beta), NR1H4 (FXR, Farnesoid X receptor), NR3C1 (GR, Glucocorticoid receptor), NR3C2 (MR, Mineralocorticoid receptor) and ESR1 (Estrogen receptor alpha) regulate AQP2 abundance and membrane translocation. PPARG induces increased AQP2 expression, sodium and water retention and edema. NR3C1 and NR1H4 also activate AQP2 expression. NR3C2 and NR1H2 reduce AQP2 expression. ESR1 mediates the inhibitory effect of estradiol on AQP2 expression (Zhang et al., 2016).
Other factors capable of regulating AQP2: extracellular osmotic pressure, insulin ( INS), nuclear factor kB (NFkB), renin/angiotensin/aldosterone system, kinins, nitric oxide, adenosine, ATP and endothelins. PTGER2 (Prostaglandin E receptor 2) also controls AQP2 expression. The phosphorylated activation of CREBBP upregulates AQP2 gene transcription (reviewed in Zhang et al., 2016).
Actin-depolymerization promotes AQP2 trafficking to the plasma membrane. TPM3 and MSN (Tropomyosin 3 and Moesin) result in F-actin destabilization. MLCK (Myosin light chain kinase) also facilitates AQP2 trafficking to the plasma membrane by regulating actin filament organization.
RHOA stimulates actin polymerization, which inhibits AQP2 trafficking to the plasma membrane.
FOSB (FosB proto-oncogene, AP-1 transcription factor subunit), CREBBP, calcineurins (protein phosphatase 3 subunits) MAPK3 / MAPK1 (so called "ERK1/ERK2") and NFAT5 (nuclear factor of activated T cells 5) increase AQP2 transcription, while NFkB reduces AQP2 gene transcription.
FOSB/ TFAP2A (transcription factor AP-2 alpha (activating enhancer binding protein 2 alpha)) (AP1/AP2) mediates clathrin-mediated endocytosis of AQP2. VTA1 (vesicle trafficking 1) facilitates AQP2 lysosomal degradation. MAPK14 (p38-MAPK) phosphorylates AQP2 to induce ubiquitination and proteasomal degradation of AQP2. Protein kinases C induce ubiquitination, endocytosis and degradation of AQP2 (Review in Vukićević et al., 2016).


Germinal AQP2 is responsible for nephrogenic non-X-linked diabetes insipidus, a disease characterized by the kidney's inability to concentrate urine (see below).

Implicated in

Note Dysregulation and dysfunction of AQP2 cause many disorders related to water balance in humans and animals, including polyuria and dilutional hyponatremia (Zan et al., 2016).
Entity Nephrogenic diabetes insipidus.
Note Nephrogenic diabetes insipidus is characterized by the kidney's inability to concentrate urine even with normal or elevated concentration of vasopressin. Polyuria/polydipsia and electrolyte imbalance is present from birth.
The antidiuretic peptide hormone arginine-vasopressin (AVP) is synthesized in the hypothalamus. Vasopressin binds its receptor AVPR2 (arginine vasopressin receptor 2) in the basolateral membrane of cells of the renal collecting ducts, inducing the vasopressin / vasopressin receptor / aquaporin-2 axis.
Nephrogenic diabetes insipidus occurs either when:
AVPR2 is mutated (90% of cases, "X-linked nephrogenic diabetes insipidus": AVPR2 locates in Xq28), or when
AQP2 is mutated (10% of cases, "nephrogenic non-X-linked diabetes insipidus"; both dominant and autosomal recessive forms have been reported. Patients with recessive forms are either homozygous, or compound heterozygous).
Nephrogenic diabetes insipidus can also be induce by lithium, demethylchlortetracycline or other drugs (Ranieri et al., 2019).
Entity Uterus endometrial carcinoma
Note There was an increased expression level of AQP2 in endometrial carcinoma, in relation to estradiol level. AQP2 was mainly located in glandular epithelial cells. An estrogen response element was found in the promoter of AQP2. In AQP2 knockdown endometrial carcinoma cells, there was an alteration of the cell morphology by decreasing the expression of ANXA2 (Annexin A2) and F-actin (Zou et al., 2011).
Entity Glioma
Note The expression of both ESR2 (Estrogen Receptor 2 (ER beta)) and AQP2 was low in glioma cells from patient tissues and glioblastoma cell lines. AQP2 promoted the transcriptional activity of LAX1 (Lymphocyte transmembrane adaptor 1) and inhibited cell invasion. ESR2 may function as AQP2 promoter in the nucleus to sustain cells stability while ESRRA (Estrogen-related receptor alpha) would acts as an antagonist of AQP2 (Wan et al. 2018).
Entity Kidney adenocarcinomay
Note A t(3;12)(p13;q13) AQP2/ FOXP1 has been found in adenocarcinoma of the kidney (Hu et al., 2018).

To be noted

Aquaporin-targeted drugs: Heavy metal ions (mercury, silver, gold) are inhibitors of aquaporin-1. The Henle loop diuretic bumetanide and analogues AqB013 and AqF026 also inhibit aquaporin-1. The quaternary ammonium compound tetraethylammonium is an inhibitor of aquaporin-1 water permeability (Verkman et al., 2014; Tomita et al., 2017).


Activation of AQP2 water channels without vasopressin: therapeutic strategies for congenital nephrogenic diabetes insipidus
Ando F, Uchida S
Clin Exp Nephrol 2018 Jun;22(3):501-507
PMID 29478202
Mechanisms of Aquaporin-Facilitated Cancer Invasion and Metastasis
De Ieso ML, Yool AJ
Front Chem 2018 Apr 25;6:135
PMID 29922644
TumorFusions: an integrative resource for cancer-associated transcript fusions
Hu X, Wang Q, Tang M, Barthel F, Amin S, Yoshihara K, Lang FM, Martinez-Ledesma E, Lee SH, Zheng S, Verhaak RGW
Nucleic Acids Res 2018 Jan 4;46(D1):D1144-D1149
PMID 29099951
Aquaporins in drug discovery and pharmacotherapy
Huber VJ, Tsujita M, Nakada T
Mol Aspects Med 2012 Oct-Dec;33(5-6):691-703
PMID 22293138
Molecular mechanisms regulating aquaporin-2 in kidney collecting duct
Jung HJ, Kwon TH
Am J Physiol Renal Physiol 2016 Dec 1;311(6):F1318-F1328
PMID 27760771
Key roles of aquaporins in tumor biology
Papadopoulos MC, Saadoun S
Biochim Biophys Acta 2015 Oct;1848(10 Pt B):2576-83
PMID 25204262
Vasopressin-aquaporin-2 pathway: recent advances in understanding water balance disorders
Ranieri M, Di Mise A, Tamma G, Valenti G
F1000Res 2019 Feb 4;8
PMID 30800291
Aquaporins: important but elusive drug targets
Verkman AS, Anderson MO, Papadopoulos MC
Nat Rev Drug Discov 2014 Apr;13(4):259-77
PMID 24625825
The Trafficking of the Water Channel Aquaporin-2 in Renal Principal Cells-a Potential Target for Pharmacological Intervention in Cardiovascular Diseases
Vukićević T, Schulz M, Faust D, Klussmann E
Front Pharmacol 2016 Feb 11;7:23
PMID 26903868
Estrogen nuclear receptors affect cell migration by altering sublocalization of AQP2 in glioma cell lines
Wan S, Jiang J, Zheng C, Wang N, Zhai X, Fei X, Wu R, Jiang X
Cell Death Discov 2018 Oct 17;4:49
PMID 30345080
The landscape and therapeutic relevance of cancer-associated transcript fusions
Yoshihara K, Wang Q, Torres-Garcia W, Zheng S, Vegesna R, Kim H, Verhaak RG
Oncogene 2015 Sep 10;34(37):4845-54
PMID 25500544
Nuclear Receptor Regulation of Aquaporin-2 in the Kidney
Zhang XY, Wang B, Guan YF
Int J Mol Sci 2016 Jul 11;17(7)
PMID 27409611
Identification of estrogen response element in the aquaporin-2 gene that mediates estrogen-induced cell migration and invasion in human endometrial carcinoma
Zou LB, Zhang RJ, Tan YJ, Ding GL, Shi S, Zhang D, He RH, Liu AX, Wang TT, Leung PC, Sheng JZ, Huang HF
J Clin Endocrinol Metab 2011 Sep;96(9):E1399-408
PMID 21715543


This paper should be referenced as such :
Huret JL
AQP2 (aquaporin 2);
Atlas Genet Cytogenet Oncol Haematol. in press
On line version :

Other Solid tumors implicated (Data extracted from papers in the Atlas) [ 1 ]
  t(3;12)(p13;q13) AQP2/FOXP1

External links

HGNC (Hugo)AQP2   634
LRG (Locus Reference Genomic)LRG_717
Entrez_Gene (NCBI)AQP2  359  aquaporin 2
GeneCards (Weizmann)AQP2
Ensembl hg19 (Hinxton)ENSG00000167580 [Gene_View]
Ensembl hg38 (Hinxton)ENSG00000167580 [Gene_View]  ENSG00000167580 [Sequence]  chr12:49950741-49958881 [Contig_View]  AQP2 [Vega]
ICGC DataPortalENSG00000167580
TCGA cBioPortalAQP2
AceView (NCBI)AQP2
Genatlas (Paris)AQP2
SOURCE (Princeton)AQP2
Genetics Home Reference (NIH)AQP2
Genomic and cartography
GoldenPath hg38 (UCSC)AQP2  -     chr12:49950741-49958881 +  12q13.12   [Description]    (hg38-Dec_2013)
GoldenPath hg19 (UCSC)AQP2  -     12q13.12   [Description]    (hg19-Feb_2009)
GoldenPathAQP2 - 12q13.12 [CytoView hg19]  AQP2 - 12q13.12 [CytoView hg38]
Mapping of homologs : NCBIAQP2 [Mapview hg19]  AQP2 [Mapview hg38]
OMIM107777   125800   
Gene and transcription
Genbank (Entrez)AI792401 AK055824 AK225940 BC042496 CR542024
RefSeq transcript (Entrez)NM_000486
RefSeq genomic (Entrez)
Consensus coding sequences : CCDS (NCBI)AQP2
Cluster EST : UnigeneHs.130730 [ NCBI ]
CGAP (NCI)Hs.130730
Alternative Splicing GalleryENSG00000167580
Gene ExpressionAQP2 [ NCBI-GEO ]   AQP2 [ EBI - ARRAY_EXPRESS ]   AQP2 [ SEEK ]   AQP2 [ MEM ]
Gene Expression Viewer (FireBrowse)AQP2 [ Firebrowse - Broad ]
SOURCE (Princeton)Expression in : [Datasets]   [Normal Tissue Atlas]  [carcinoma Classsification]  [NCI60]
GenevestigatorExpression in : [tissues]  [cell-lines]  [cancer]  [perturbations]  
BioGPS (Tissue expression)359
GTEX Portal (Tissue expression)AQP2
Human Protein AtlasENSG00000167580-AQP2 [pathology]   [cell]   [tissue]
Protein : pattern, domain, 3D structure
UniProt/SwissProtP41181   [function]  [subcellular_location]  [family_and_domains]  [pathology_and_biotech]  [ptm_processing]  [expression]  [interaction]
NextProtP41181  [Sequence]  [Exons]  [Medical]  [Publications]
With graphics : InterProP41181
Splice isoforms : SwissVarP41181
Domaine pattern : Prosite (Expaxy)MIP (PS00221)   
Domains : Interpro (EBI)Aquaporin-like    Aquaporin_transptr    MIP    MIP_CS   
Domain families : Pfam (Sanger)MIP (PF00230)   
Domain families : Pfam (NCBI)pfam00230   
Conserved Domain (NCBI)AQP2
DMDM Disease mutations359
Blocks (Seattle)AQP2
PDB (RSDB)4NEF    4OJ2   
PDB Europe4NEF    4OJ2   
PDB (PDBSum)4NEF    4OJ2   
PDB (IMB)4NEF    4OJ2   
Structural Biology KnowledgeBase4NEF    4OJ2   
SCOP (Structural Classification of Proteins)4NEF    4OJ2   
CATH (Classification of proteins structures)4NEF    4OJ2   
Human Protein Atlas [tissue]ENSG00000167580-AQP2 [tissue]
Peptide AtlasP41181
IPIIPI00012818   IPI01021050   IPI01021169   
Protein Interaction databases
IntAct (EBI)P41181
Ontologies - Pathways
Ontology : AmiGOrenal water homeostasis  renal water transport  water transmembrane transporter activity  protein binding  Golgi apparatus  plasma membrane  plasma membrane  plasma membrane  water transport  water transport  excretion  glycerol transmembrane transporter activity  water channel activity  water channel activity  glycerol transport  membrane  integral component of membrane  basolateral plasma membrane  apical plasma membrane  apical plasma membrane  apical plasma membrane  transport vesicle membrane  cellular response to water deprivation  recycling endosome  transmembrane transport  extracellular exosome  extracellular exosome  cellular response to copper ion  cellular response to mercury ion  metanephric collecting duct development  
Ontology : EGO-EBIrenal water homeostasis  renal water transport  water transmembrane transporter activity  protein binding  Golgi apparatus  plasma membrane  plasma membrane  plasma membrane  water transport  water transport  excretion  glycerol transmembrane transporter activity  water channel activity  water channel activity  glycerol transport  membrane  integral component of membrane  basolateral plasma membrane  apical plasma membrane  apical plasma membrane  apical plasma membrane  transport vesicle membrane  cellular response to water deprivation  recycling endosome  transmembrane transport  extracellular exosome  extracellular exosome  cellular response to copper ion  cellular response to mercury ion  metanephric collecting duct development  
Pathways : KEGGVasopressin-regulated water reabsorption   
REACTOMEP41181 [protein]
REACTOME PathwaysR-HSA-432047 [pathway]   
NDEx NetworkAQP2
Atlas of Cancer Signalling NetworkAQP2
Wikipedia pathwaysAQP2
Orthology - Evolution
GeneTree (enSembl)ENSG00000167580
Phylogenetic Trees/Animal Genes : TreeFamAQP2
Homologs : HomoloGeneAQP2
Homology/Alignments : Family Browser (UCSC)AQP2
Gene fusions - Rearrangements
Fusion : MitelmanAQP2/FOXP1 [12q13.12/3p13]  
Fusion PortalAQP2 12q13.12 FOXP1 3p13 KIRC
Fusion : FusionGDB2285   
Fusion : Fusion_HubAQP2--FOXP1    AQP2--GPX3    LIR--AQP2    MAST4--AQP2   
Fusion : QuiverAQP2
Polymorphisms : SNP and Copy number variants
NCBI Variation ViewerAQP2 [hg38]
dbSNP Single Nucleotide Polymorphism (NCBI)AQP2
Exome Variant ServerAQP2
ExAC (Exome Aggregation Consortium)ENSG00000167580
GNOMAD BrowserENSG00000167580
Varsome BrowserAQP2
Genetic variants : HAPMAP359
Genomic Variants (DGV)AQP2 [DGVbeta]
DECIPHERAQP2 [patients]   [syndromes]   [variants]   [genes]  
CONAN: Copy Number AnalysisAQP2 
ICGC Data PortalAQP2 
TCGA Data PortalAQP2 
Broad Tumor PortalAQP2
OASIS PortalAQP2 [ Somatic mutations - Copy number]
Somatic Mutations in Cancer : COSMICAQP2  [overview]  [genome browser]  [tissue]  [distribution]  
Mutations and Diseases : HGMDAQP2
LOVD (Leiden Open Variation Database)Whole genome datasets
LOVD (Leiden Open Variation Database)LOVD - Leiden Open Variation Database
LOVD (Leiden Open Variation Database)LOVD 3.0 shared installation
BioMutasearch AQP2
DgiDB (Drug Gene Interaction Database)AQP2
DoCM (Curated mutations)AQP2 (select the gene name)
CIViC (Clinical Interpretations of Variants in Cancer)AQP2 (select a term)
NCG5 (London)AQP2
Cancer3DAQP2(select the gene name)
Impact of mutations[PolyPhen2] [Provean] [Buck Institute : MutDB] [Mutation Assessor] [Mutanalyser]
OMIM107777    125800   
Genetic Testing Registry AQP2
NextProtP41181 [Medical]
Target ValidationAQP2
Huge Navigator AQP2 [HugePedia]
snp3D : Map Gene to Disease359
BioCentury BCIQAQP2
Clinical trials, drugs, therapy
Chemical/Protein Interactions : CTD359
Chemical/Pharm GKB GenePA24920
Clinical trialAQP2
canSAR (ICR)AQP2 (select the gene name)
DataMed IndexAQP2
PubMed168 Pubmed reference(s) in Entrez
GeneRIFsGene References Into Functions (Entrez)
REVIEW articlesautomatic search in PubMed
Last year publicationsautomatic search in PubMed

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