Biology:Aquaporin-2

Short description: Protein-coding gene in the species Homo sapiens

Generic protein structure example

Aquaporin-2 (AQP-2) is found in the apical cell membranes of the kidney's collecting duct principal cells and in intracellular vesicles located throughout the cell. It is encoded by the AQP2 gene.

Regulation

It is the only aquaporin regulated by vasopressin. 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. When it is needed, vasopressin binds to the cell surface vasopressin receptor thereby 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. 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

Further reading

• "Nephrogenic diabetes insipidus". Advances in Chronic Kidney Disease 13 (2): 96–104. April 2006. doi:10.1053/j.ackd.2006.01.006. PMID 16580609. http://discovery.ucl.ac.uk/1540833/1/Bockenhauer_Bichet%252011%2520janv%25202017%2520references%2520in%2520sequence%2520MOP290219%2520Bichet%2520MS%255B1%255D.pdf. 
• "Bypassing vasopressin receptor signaling pathways in nephrogenic diabetes insipidus". Seminars in Nephrology 28 (3): 266–78. May 2008. doi:10.1016/j.semnephrol.2008.03.010. PMID 18519087. 
• "Cell biological aspects of the vasopressin type-2 receptor and aquaporin 2 water channel in nephrogenic diabetes insipidus". American Journal of Physiology. Renal Physiology 291 (2): F257–70. August 2006. doi:10.1152/ajprenal.00491.2005. PMID 16825342. https://repository.ubn.ru.nl/bitstream/2066/50267/1/50267.pdf. 
• "Cloning, characterization, and chromosomal mapping of human aquaporin of collecting duct". The Journal of Clinical Investigation 93 (3): 1250–6. March 1994. doi:10.1172/JCI117079. PMID 7510718. 
• "Assignment of the human gene for the water channel of renal collecting duct Aquaporin 2 (AQP2) to chromosome 12 region q12-->q13". Cytogenetics and Cell Genetics 66 (4): 260–2. 1994. doi:10.1159/000133707. PMID 7512890. 
• "Isolation of human aquaporin-CD gene". The Journal of Biological Chemistry 269 (38): 23451–5. September 1994. doi:10.1016/S0021-9258(17)31537-5. PMID 7522228. 
• "Patients with autosomal nephrogenic diabetes insipidus homozygous for mutations in the aquaporin 2 water-channel gene". American Journal of Human Genetics 55 (4): 648–52. October 1994. PMID 7524315. 
• "Human AQP2 and MIP genes, two members of the MIP family, map within chromosome band 12q13 on the basis of two-color FISH". Cytogenetics and Cell Genetics 68 (1–2): 45–8. 1994. doi:10.1159/000133885. PMID 7525161. 
• "Vasopressin increases water permeability of kidney collecting duct by inducing translocation of aquaporin-CD water channels to plasma membrane". Proceedings of the National Academy of Sciences of the United States of America 92 (4): 1013–7. February 1995. doi:10.1073/pnas.92.4.1013. PMID 7532304. Bibcode: 1995PNAS...92.1013N. 
• "The ins and outs of aquaporin-2 trafficking". American Journal of Physiology. Renal Physiology 284 (5): F893–901. May 2003. doi:10.1152/ajprenal.00387.2002. PMID 12676734. 
• "Oligo-capping: a simple method to replace the cap structure of eukaryotic mRNAs with oligoribonucleotides". Gene 138 (1–2): 171–4. January 1994. doi:10.1016/0378-1119(94)90802-8. PMID 8125298. 
• "Requirement of human renal water channel aquaporin-2 for vasopressin-dependent concentration of urine". Science 264 (5155): 92–5. April 1994. doi:10.1126/science.8140421. PMID 8140421. Bibcode: 1994Sci...264...92D. 
• "Two novel mutations in the aquaporin-2 and the vasopressin V2 receptor genes in patients with congenital nephrogenic diabetes insipidus". Human Genetics 98 (5): 587–9. November 1996. doi:10.1007/s004390050264. PMID 8882880. 
• "New mutations in the AQP2 gene in nephrogenic diabetes insipidus resulting in functional but misrouted water channels". Journal of the American Society of Nephrology 8 (2): 242–8. February 1997. doi:10.1681/ASN.V82242. PMID 9048343. 
• "Closely spaced tandem arrangement of AQP2, AQP5, and AQP6 genes in a 27-kilobase segment at chromosome locus 12q13". Genomics 43 (3): 387–9. August 1997. doi:10.1006/geno.1997.4836. PMID 9268644. 
• "Identification and characterization of aquaporin-2 water channel mutations causing nephrogenic diabetes insipidus with partial vasopressin response". Human Molecular Genetics 6 (11): 1865–71. October 1997. doi:10.1093/hmg/6.11.1865. PMID 9302264. 
• "Construction and characterization of a full length-enriched and a 5'-end-enriched cDNA library". Gene 200 (1–2): 149–56. October 1997. doi:10.1016/S0378-1119(97)00411-3. PMID 9373149. 
• "Mutations in the vasopressin V2 receptor and aquaporin-2 genes in 12 families with congenital nephrogenic diabetes insipidus". Journal of the American Society of Nephrology 8 (12): 1855–62. December 1997. doi:10.1681/ASN.V8121855. PMID 9402087. 
• "Aquaporin-2, a vasopressin-sensitive water channel, and nephrogenic diabetes insipidus". Internal Medicine 37 (2): 215–7. February 1998. doi:10.2169/internalmedicine.37.215. PMID 9550615. 
• "An aquaporin-2 water channel mutant which causes autosomal dominant nephrogenic diabetes insipidus is retained in the Golgi complex". The Journal of Clinical Investigation 102 (1): 57–66. July 1998. doi:10.1172/JCI2605. PMID 9649557. 
• "Novel mutations in aquaporin-2 gene in female siblings with nephrogenic diabetes insipidus: evidence of disrupted water channel function". The Journal of Clinical Endocrinology and Metabolism 83 (9): 3205–9. September 1998. doi:10.1210/jcem.83.9.5074. PMID 9745427. 
• "Urinary excretion of aquaporin-2 water channel differentiates psychogenic polydipsia from central diabetes insipidus". The Journal of Clinical Endocrinology and Metabolism 84 (6): 2235–7. June 1999. doi:10.1210/jcem.84.6.5715. 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)
• Human AQP2 genome location and AQP2 gene details page in the UCSC Genome Browser.
• Overview of all the structural information available in the PDB for UniProt: P41181 (Aquaporin-2) at the PDBe-KB.