Aquaporin-9 Explained

Aquaporin-9 (AQP-9) is a protein that in humans is encoded by the AQP9 gene.^[1]

The aquaporins/major intrinsic protein are a family of water-selective membrane channels. Aquaporin-9 has greater sequence similarity with AQP3 and AQP7 and they may be a subfamily. Aquaporin-9 allows passage of a wide variety of noncharged solutes. AQP-9 stimulates urea transport and osmotic water permeability; there are contradicting reports about its role in providing glycerol permeability. Aquaporin-9 may also have some role in specialized leukocyte functions such as immunological response and bactericidal activity.

Further reading

• Ishibashi K, Kuwahara M, Gu Y . Cloning and functional expression of a new aquaporin (AQP9) abundantly expressed in the peripheral leukocytes permeable to water and urea, but not to glycerol . Biochem. Biophys. Res. Commun. . 244 . 1 . 268–74 . 1998 . 9514918 . 10.1006/bbrc.1998.8252 . etal.
• Tsukaguchi H, Shayakul C, Berger UV . Molecular characterization of a broad selectivity neutral solute channel . J. Biol. Chem. . 273 . 38 . 24737–43 . 1998 . 9733774 . 10.1074/jbc.273.38.24737 . etal. free .
• Tsukaguchi H, Weremowicz S, Morton CC, Hediger MA . Functional and molecular characterization of the human neutral solute channel aquaporin-9 . Am. J. Physiol. . 277 . 5 Pt 2 . F685–96 . 1999 . 10564231 . 10.1152/ajprenal.1999.277.5.F685. 4516233 .
• Pastor-Soler N, Bagnis C, Sabolic I . Aquaporin 9 expression along the male reproductive tract . Biol. Reprod. . 65 . 2 . 384–93 . 2001 . 11466204 . 10.1095/biolreprod65.2.384 . etal. free .
• Damiano A, Zotta E, Goldstein J . Water channel proteins AQP3 and AQP9 are present in syncytiotrophoblast of human term placenta . Placenta . 22 . 8–9 . 776–81 . 2001 . 11597198 . 10.1053/plac.2001.0717 . etal.
• Strausberg RL, Feingold EA, Grouse LH . Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences . Proc. Natl. Acad. Sci. U.S.A. . 99 . 26 . 16899–903 . 2003 . 12477932 . 10.1073/pnas.242603899 . 139241 . 2002PNAS...9916899M . etal. free .
• Okada S, Misaka T, Matsumoto I . Aquaporin-9 is expressed in a mucus-secreting goblet cell subset in the small intestine . FEBS Lett. . 540 . 1–3 . 157–62 . 2003 . 12681500 . 10.1016/S0014-5793(03)00256-4 . 20184558 . etal. free .
• Bhattacharjee H, Carbrey J, Rosen BP, Mukhopadhyay R . Drug uptake and pharmacological modulation of drug sensitivity in leukemia by AQP9 . Biochem. Biophys. Res. Commun. . 322 . 3 . 836–41 . 2004 . 15336539 . 10.1016/j.bbrc.2004.08.002 .
• Gerhard DS, Wagner L, Feingold EA . The Status, Quality, and Expansion of the NIH Full-Length cDNA Project: The Mammalian Gene Collection (MGC) . Genome Res. . 14 . 10B . 2121–7 . 2004 . 15489334 . 10.1101/gr.2596504 . 528928 . etal.
• Wang S, Chen J, Beall M . Expression of aquaporin 9 in human chorioamniotic membranes and placenta . Am. J. Obstet. Gynecol. . 191 . 6 . 2160–7 . 2005 . 15592307 . 10.1016/j.ajog.2004.05.089 . etal.
• Damiano AE, Zotta E, Ibarra C . Functional and molecular expression of AQP9 channel and UT-A transporter in normal and preeclamptic human placentas . Placenta . 27 . 11–12 . 1073–81 . 2006 . 16480766 . 10.1016/j.placenta.2005.11.014 .
• Olsen JV, Blagoev B, Gnad F . Global, in vivo, and site-specific phosphorylation dynamics in signaling networks . Cell . 127 . 3 . 635–48 . 2006 . 17081983 . 10.1016/j.cell.2006.09.026 . 7827573 . etal. free .
• Loitto VM, Huang C, Sigal YJ, Jacobson K . Filopodia are induced by aquaporin-9 expression . Exp. Cell Res. . 313 . 7 . 1295–306 . 2007 . 17346701 . 10.1016/j.yexcr.2007.01.023 .
• Warth A, Mittelbronn M, Hülper P . Expression of the water channel protein aquaporin-9 in malignant brain tumors . Appl. Immunohistochem. Mol. Morphol. . 15 . 2 . 193–8 . 2007 . 17525633 . 10.1097/01.pai.0000213110.05108.e9 . 24070875 . etal.

Notes and References

1. Web site: Entrez Gene: AQP9 aquaporin 9.