Aquaporin 2

Aquaporin 2 (collecting duct)
Available structures PDB Ortholog search: PDBe, RCSB List of PDB id codes 4NEF​, 4OJ2​
Identifiers
Symbols	AQP2 ; AQP-CD; WCH-CD
External IDs	OMIM: 107777 MGI: 1096865 HomoloGene: 20137 IUPHAR: 689 GeneCards: AQP2 Gene
Gene ontology Molecular function • water transmembrane transporter activity • glycerol transmembrane transporter activity • water channel activity • glycerol channel activity Cellular component • Golgi apparatus • plasma membrane • integral component of plasma membrane • membrane • basolateral plasma membrane • apical plasma membrane • transport vesicle membrane • recycling endosome • extracellular exosome Biological process • renal water homeostasis • renal water transport • water transport • excretion • cellular water homeostasis • glycerol transport • ion transmembrane transport • cellular response to water deprivation • transmembrane transport • cellular response to copper ion • cellular response to mercury ion • metanephric collecting duct development Sources: Amigo / QuickGO
RNA expression pattern
More reference expression data
Orthologs
Species	Human	Mouse
Entrez	359	11827
Ensembl	ENSG00000167580	ENSMUSG00000023013
UniProt	P41181	P56402
RefSeq (mRNA)	NM_000486	NM_009699
RefSeq (protein)	NP_000477	NP_033829
Location (UCSC)	Chr 12: 49.95 – 49.96 Mb	Chr 15: 99.58 – 99.58 Mb
PubMed search

AQP2 is found in the apical cell membranes of the kidney's collecting duct principal cells and in intracellular vesicles located throughout the cell.

Regulation

It is the only aquaporin regulated by vasopressin.^[1] The basic job of aquaporin 2 is to reabsorb water from the urine while its being removed from the blood by the kidney. Aquaporin 2 is in kidney epithelial cells and usually lies dormant in intracellular vesicle membranes, but when it is needed vasopressin binds to the cell surface vasopressin receptor, activating a signaling pathway that causes the aquaporin 2 containing vesicles to fuse with the plasma membrane so the aquaporin 2 can be used by the cell.^[2]

This aquaporin is regulated in two ways by the peptide hormone vasopressin:

• short-term regulation (minutes) through trafficking of AQP2 vesicles to the apical region where they fuse with the apical plasma membrane
• long-term regulation (days) through an increase in AQP2 gene expression.

This aquaporin is also regulated by food intake. Fasting reduces expression of this aquaporin independently of vasopressin.

Clinical significance

Mutations in this channel are associated with nephrogenic diabetes insipidus, which can be autosomal dominant or recessive. Mutations in the vasopressin receptor cause a similar X-linked phenotype.

Lithium, which is often used to treat bipolar disorder, can cause acquired diabetes insipidus (characterized by the excretion of large volumes of dilute urine) by decreasing the expression of the AQP2 gene.

The expression of the AQP2 gene is increased during conditions associated with water retention such as pregnancy and congestive heart failure.

See also

• Aquaporin

References

1. Dibas AI, Mia AJ, Yorio T (1998). "Aquaporins (water channels): role in vasopressin-activated water transport". Proc. Soc. Exp. Biol. Med. 219 (3): 183–99. doi:10.3181/00379727-219-44332. PMID 9824541.
2. Lodish, Harvey F. Molecular Cell Biology. New York: W.H. Freeman, 2008. Print. 445.

Further reading

• Bichet DG (2006). "Nephrogenic diabetes insipidus". Advances in chronic kidney disease 13 (2): 96–104. doi:10.1053/j.ackd.2006.01.006. PMID 16580609.
• Bouley R, Hasler U, Lu HAJ, Nunes P, Brown D (2008). "Bypassing vasopressin signaling pathways in nephrogenic diabetes insipidus". Sem. Nephrol. 28 (3): 266–78. doi:10.1016/j.semnephrol.2008.03.010. PMC 2494582. PMID 18519087.
• Robben JH, Knoers NV, Deen PM (2006). "Cell biological aspects of the vasopressin type-2 receptor and aquaporin 2 water channel in nephrogenic diabetes insipidus". Am. J. Physiol. Renal Physiol. 291 (2): F257–70. doi:10.1152/ajprenal.00491.2005. PMID 16825342.
• Sasaki S, Fushimi K, Saito H, et al. (1994). "Cloning, characterization, and chromosomal mapping of human aquaporin of collecting duct". J. Clin. Invest. 93 (3): 1250–6. doi:10.1172/JCI117079. PMC 294077. PMID 7510718.
• Deen PM, Weghuis DO, Sinke RJ, et al. (1994). "Assignment of the human gene for the water channel of renal collecting duct Aquaporin 2 (AQP2) to chromosome 12 region q12→q13". Cytogenet. Cell Genet. 66 (4): 260–2. doi:10.1159/000133707. PMID 7512890.
• Uchida S, Sasaki S, Fushimi K, Marumo F (1994). "Isolation of human aquaporin-CD gene". J. Biol. Chem. 269 (38): 23451–5. PMID 7522228.
• van Lieburg AF, Verdijk MA, Knoers VV, et al. (1994). "Patients with autosomal nephrogenic diabetes insipidus homozygous for mutations in the aquaporin 2 water-channel gene". Am. J. Hum. Genet. 55 (4): 648–52. PMC 1918308. PMID 7524315.
• Saito F, Sasaki S, Chepelinsky AB, et al. (1994). "Human AQP2 and MIP genes, two members of the MIP family, map within chromosome band 12q13 on the basis of two-color FISH". Cytogenet. Cell Genet. 68 (1–2): 45–8. doi:10.1159/000133885. PMID 7525161.
• Nielsen S, Chou CL, Marples D, et al. (1995). "Vasopressin increases water permeability of kidney collecting duct by inducing translocation of aquaporin-CD water channels to plasma membrane". Proc. Natl. Acad. Sci. U.S.A. 92 (4): 1013–7. doi:10.1073/pnas.92.4.1013. PMC 42627. PMID 7532304.
• Brown D (2003). "The ins and outs of aquaporin 2 trafficking". Am. J. Physiol. Renal Physiol. 284 (5): F893–901. doi:10.1152/ajprenal.00387.2002. PMID 12676734.
• Maruyama K, Sugano S (1994). "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene 138 (1–2): 171–4. doi:10.1016/0378-1119(94)90802-8. PMID 8125298.
• Deen PM, Verdijk MA, Knoers NV, et al. (1994). "Requirement of human renal water channel aquaporin-2 for vasopressin-dependent concentration of urine". Science 264 (5155): 92–5. doi:10.1126/science.8140421. PMID 8140421.
• Oksche A, Möller A, Dickson J, et al. (1996). "Two novel mutations in the aquaporin-2 and the vasopressin V2 receptor genes in patients with congenital nephrogenic diabetes insipidus". Hum. Genet. 98 (5): 587–9. doi:10.1007/s004390050264. PMID 8882880.
• Mulders SM, Knoers NV, Van Lieburg AF, et al. (1997). "New mutations in the AQP2 gene in nephrogenic diabetes insipidus resulting in functional but misrouted water channels". J. Am. Soc. Nephrol. 8 (2): 242–8. PMID 9048343.
• Ma T, Yang B, Umenishi F, Verkman AS (1997). "Closely spaced tandem arrangement of AQP2, AQP5, and AQP6 genes in a 27-kilobase segment at chromosome locus 12q13". Genomics 43 (3): 387–9. doi:10.1006/geno.1997.4836. PMID 9268644.
• Canfield MC, Tamarappoo BK, Moses AM, et al. (1998). "Identification and characterization of aquaporin-2 water channel mutations causing nephrogenic diabetes insipidus with partial vasopressin response". Hum. Mol. Genet. 6 (11): 1865–71. doi:10.1093/hmg/6.11.1865. PMID 9302264.
• Suzuki Y, Yoshitomo-Nakagawa K, Maruyama K, et al. (1997). "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene 200 (1–2): 149–56. doi:10.1016/S0378-1119(97)00411-3. PMID 9373149.
• Vargas-Poussou R, Forestier L, Dautzenberg MD, et al. (1998). "Mutations in the vasopressin V2 receptor and aquaporin-2 genes in 12 families with congenital nephrogenic diabetes insipidus". J. Am. Soc. Nephrol. 8 (12): 1855–62. PMID 9402087.
• Kuwahara M (1998). "Aquaporin-2, a vasopressin-sensitive water channel, and nephrogenic diabetes insipidus". Intern. Med. 37 (2): 215–7. doi:10.2169/internalmedicine.37.215. PMID 9550615.
• Mulders SM, Bichet DG, Rijss JP, et al. (1998). "An aquaporin-2 water channel mutant which causes autosomal dominant nephrogenic diabetes insipidus is retained in the Golgi complex". J. Clin. Invest. 102 (1): 57–66. doi:10.1172/JCI2605. PMC 509065. PMID 9649557.
• Goji K, Kuwahara M, Gu Y, et al. (1998). "Novel mutations in aquaporin-2 gene in female siblings with nephrogenic diabetes insipidus: evidence of disrupted water channel function". J. Clin. Endocrinol. Metab. 83 (9): 3205–9. doi:10.1210/jc.83.9.3205. PMID 9745427.
• Saito T, Ishikawa S, Ito T, et al. (1999). "Urinary excretion of aquaporin-2 water channel differentiates psychogenic polydipsia from central diabetes insipidus". J. Clin. Endocrinol. Metab. 84 (6): 2235–7. doi:10.1210/jc.84.6.2235. PMID 10372737.

External links

• GeneReviews/NCBI/NIH/UW entry on Nephrogenic Diabetes Insipidus
• Aquaporin 2 at the US National Library of Medicine Medical Subject Headings (MeSH)