Disease relevance of AQP7

• Recent studies have shown that the absence of AQP7 expression in fat cells increases glycerol kinase activity, boosting triacylglycerol synthesis and ultimately leading to obesity [1].
• It is likely that up-regulated expression of AQP2 mRNA and down-regulated expression of AQP7 mRNA in the rat inner ear caused by vasopressin induce an increased production and a decreased absorption of endolymph, resulting in endolymphatic hydrops [2].
• Much further work is needed to define whether the overexpression of AQP9 plays a direct role either in the pathogenesis or in the adaptative response of preeclampsia [3].
• Furthermore, a lack of AQP7 expression in sperm may be an underlying mechanism of male infertility [4].
• Furthermore, after transient brain ischemia, AQP9 expression is increased in astrocytes and its regulation may implicate the MAP-kinase pathways stimulated in such pathological conditions [5].

Psychiatry related information on AQP7

• The aim of the present study was to compare the AQP7 gene expression in subcutaneous abdominal fat in lean vs. obese high fat intakers with a similar daily physical activity pattern [6].

High impact information on AQP7

• Multifunctional aquaglyceroporins AQP3, AQP7, and AQP9 are permeated by water, glycerol, and some other solutes [7].
• In mammals, there are currently 10 families of water channels, referred to as aquaporins (AQP): AQP0-AQP9 [8].
• We report that two members of the aquaporin family, AQP3 and AQP7, are expressed in immature DCs and are downregulated after maturation [9].
• Little AQP7 or AQP9 mRNA was detected by reverse transcription-PCR in either cell line, whereas AQP3 mRNA expression was 2-fold lower in R15 cells than in CL3 cells [10].
• Surprisingly, several PPARgamma target genes were up-regulated in PAX8-PPARgamma-positive FTCs such as angiopoietin-like 4 and aquaporin 7 [11].

Chemical compound and disease context of AQP7

• The down-regulation of the AQP7 gene could be implicated in the susceptibility to obesity by reducing glycerol release and promoting the accumulation of lipids in the adipose tissue [6].
• We also evaluated AQP9 protein expression in cultured human hepatoma cells treated with oleic acid, Wy14643, or RSG [12].
• Oleic acid and Wy14643 upregulated AQP9 protein expression in cultured human hepatoma cells in a dose-dependent manner [12].

Biological context of AQP7

• A 1408 bp cDNA was sequenced (designated rAQP9L) with a 885 bp open reading frame encoding a 295 amino acid hydrophobic protein. rAQP9L has the greatest amino-acid sequence identity with human AQP9 (75%) and a less homology with AQP3 (49%) and AQP7 (47%) [13].
• These results suggest that the increase of urea uptake in preeclamptic pregnancies could be attributed to an increase of expression of UT-A more than AQP9 proteins [3].
• The large discrepancy of tissue distribution between hAQP9 and rAQP9L suggest that rAQP9L is a new aquaporin, which is involved in transport of urea as well as water in liver [13].
• AQP7 may be involved in the maintenance of sperm motility [4].
• PURPOSE: We have previously reported the expression of aquaporin-7 (AQP7) in the rat testis and cloned human AQP7 from the testicular cDNA library [4].

Anatomical context of AQP7

• Thus, AQP7 operates as a glycerol channel in vivo, whereby adipocyte glycerol permeability has a key role in the regulation of fat accumulation [1].
• In summary, our data show that the AQP7 gene is differentially expressed in adipose tissue of lean and obese individuals [6].
• Aquaporins are a family of intrinsic membrane proteins that function as water-selective channels (except aquaporin-3 and aquaporin-7, which are permeable to urea and glycerol as well) in the plasma membranes of many cells [14].
• Aquaporin-7 appears to play a role in the cryopreservation of the sperm whereas aquaporin-8 is responsible for the secretion of pancreatic juice [14].
• AQP9 is present in the liver and leukocytes [15].

Associations of AQP7 with chemical compounds

• AQP7 also facilitated glycerol and urea transport by 5- and 9-fold, respectively [16].
• The expression of AQP7 in oocytes stimulated the osmotic water permeability by 10-fold which was not inhibited by 0.3 mM mercury chloride [16].
• A 2-week RSG treatment increased AQP7 mRNA levels in the mesenteric fat, but not in the epididymal fat of OLETF rats [12].
• Thiazolidinedione (TZD) has been shown to increase adipose AQP7 and induce glycerol kinase (GlyK) which is nearly absent in adipocytes [12].
• In addition, we observed an increase of AQP9 expression in preeclamptic placenta with a lack of functionality of AQP9 for water and mannitol [3].
• Circulating glycerol concentration was lower in severely obese subjects, but no correlation with AQP7 adipose tissue expression was observed [17].

Other interactions of AQP7

• AQP0, AQP2, and AQP9 were not found in any corneas [18].

Analytical, diagnostic and therapeutic context of AQP7

• The microarray analysis revealed that AQP7 gene was down-regulated in obese compared to lean subjects [6].
• The immunohistochemistry of testis localized the AQP7 expression at late spermatids and at maturing sperms [16].
• In situ hybridization of testis revealed the expression of AQP7 at late spermatids in seminiferous tubules [16].
• Gel electrophoresis of the reverse transcription-polymerase chain reaction (RT-PCR) product of total RNA samples of normal human or mouse muscles by using oligonucleotide primers for human or mouse AQP7 showed a band of 328 or 369 basepairs, which corresponded to the basepair length between two primers of AQP7 [19].
• The requirement for Phe-64 and Arg-219 in arsenic trioxide translocation was examined by site-directed mutagenesis of rAQP9, taking advantage of the fact that rat AQP9 catalyzes (73)As(OH)(3) uptake in Saccharomyces cerevisiae and in oocytes [20].

References