Disease relevance of AQP5

• We tested the hypothesis that orally administered human interferon-alpha (HuIFN-alpha) benefits persons with xerostomia by augmenting the production of AQP5 protein by parotid gland epithelium [1].
• By contrast, cytoplasmic AQP5 was seen in patients with Sjögren's syndrome [2].
• Healthy controls and patients with Mikulicz's disease or non-Sjögren's syndrome dry eye had the expected apical distribution of AQP5 in lacrimal acinar cells [2].
• The AQP5 distribution in biopsies from patients with other dry mouth disorders, such as non-specific sialoadenitis or sarcoidosis, was similar to biopsies from control subjects [3].
• Of all the epithelial ovarian malignant tumors, the AQP5 expression in cases with ascites volume more than 1000 ml was higher than that of ascites volume less than 500 ml (P < 0.05) [4].

High impact information on AQP5

• Distribution of salivary aquaporin-5 in Sjögren's syndrome [5].
• We assessed the distribution of aquaporin-5 (AQP5) in lacrimal gland biopsy samples [2].
• Expression of N terminus-deleted AQP5 suppressed TRPV4 activation and RVD but not cell swelling [6].
• Aquaporin 5 expression in salivary gland was inhibited by radiation; and HSP25 transfer to salivary gland prevented this alteration [7].
• Cells transfected with human AQP4 and AQP5, which are also expressed in airway epithelia, were insensitive to nickel and extracellular acidification [8].

Chemical compound and disease context of AQP5

• Expression of aquaporin-5 in and fluid secretion from immortalized human salivary gland ductal cells by treatment with 5-aza-2'-deoxycytidine: a possibility for improvement of xerostomia in patients with Sjögren's syndrome [9].

Biological context of AQP5

• Closely spaced tandem arrangement of AQP2, AQP5, and AQP6 genes in a 27-kilobase segment at chromosome locus 12q13 [10].
• We conclude that IFN-alpha upregulates AQP5 gene expression in human parotid acinar cells in vitro [1].
• We have examined the mechanism of regulatory volume decrease (RVD) in salivary gland cells and report a novel association between osmosensing TRPV4 (transient receptor potential vanalloid 4) and AQP5 (aquaporin 5), which is required for regulating water permeability and cell volume [6].
• A recombinant plasmid (pShAQP5) containing small hairpin RNA expression cassette targeting AQP5 sequence was constructed [11].
• However, the significant suppression of AQP5 protein did not appear until day 5 after transfection [12].

Anatomical context of AQP5

• In nose and bronchial epithelia, AQP5 is expressed at the apical membrane of columnar cells of the superficial epithelium and submucosal gland acinar cells [13].
• Aquaporin-5 (AQP5) is uniquely present in lacrimal and salivary glands, where it accounts for normal tear and saliva production [1].
• AQP5 was constitutively expressed in human parotid gland tissue, with AQP5 protein restricted to the plasma membranes and cytoplasmic vesicles of acinar cells [1].
• AQP5 was found in epithelial cells of all corneas [14].
• AQP5 is localized in the apical membranes of several different epithelia in vivo, and in stably transfected MDCK-II cells grown as a polarized monolayer [15].

Associations of AQP5 with chemical compounds

• Attachment of a FLAG epitope to the NH2 terminus of AQP5 (AQP5(flag) construct) also did not perturb apical localization [15].
• Furthermore, apical, but not basolateral, application of Hg(2+) significantly reduces the transepithelial osmotic permeability, suggesting that apical AQP1 and AQP5 may contribute significantly to fluid secretion [16].
• Aquaporin-5 (AQP5) localizes in lipid rafts under control conditions and is induced to traffic to the apical plasma membrane in interlobular ducts of rat parotid glands by the activation of M3 muscarinic acetylcholine receptors or alpha1-adrenoceptors [17].
• An increase in apical AQP5 protein expression was found in response to progesterone alone or in combination with oestrogen, which is similar to that seen at the time of implantation [18].
• Thus, in this study, we demonstrate that an immortalized normal human salivary gland ductal cell (NS-SV-DC) line, lacking the expression of AQP5, acquires AQP5 gene expression in response to treatment with 5-aza-2'-deoxycytidine (5-Aza-CdR), a DNA demethylating agent [9].

Regulatory relationships of AQP5

• Our researchers have analyzed the changes of AQP5 expression induced by vector-based short hairpin RNA (shRNA) in the human airway submucosal gland cell line (SPC-A1) and observed its regulation on the expression of MUC5AC gene [12].

Other interactions of AQP5

• Only AQP1, AQP3, and AQP5 mRNAs were present at significant levels [19].
• We conclude that AQP3 and AQP5 together may provide a pathway for transcellular osmotic water flow in the formation of the primary saliva [19].
• Cells from three human parotid glands were cultured with and without human lymphoblastoid IFN-alpha, and assayed for AQP5 mRNA levels by reverse transcriptase polymerase chain reaction (RT-PCR), and AQP5 protein levels by Western blot [1].
• This is the first reliable investigation of the regulation of MUC5AC mucin secretion by silencing AQP5 [11].
• The concentrations of lactoerrin, EGF, and AQP5 were measured by enzyme-linked immunosorbent assay [20].

Analytical, diagnostic and therapeutic context of AQP5

• Western blot analysis of AQP1 and AQP5 expression in the glands revealed that protein abundance decreased in a similar fashion [21].
• Intracellular localization of AQP5 protein was done using confocal microscopy [1].
• Localizations of AQP5 and MUC5AC in SPC-A1cells were detected by Immunofluorescence [12].
• Using primers against highly conserved regions of mammalian and bird aquaporins in RT-PCR experiments, we amplified products derived from duck (Anas platyrhynchos) nasal gland RNA that were identified as homologues of mammalian and chicken aquaporin 1 and aquaporin 5 cDNAs by sequencing [21].
• Despite this implication, AQP5 mRNA levels were almost the same between the two groups by Northern blotting, suggesting the irrelevance of transcriptional regulation for this diversity [22].

References