Disease relevance of AQP1

• This study is the first demonstration of the induction of AQP1 and AQP4 on reactive astrocytes in an acute brain injury, such as SAH [1].
• The purpose of this study was to investigate the expression of AQP1 and AQP4 in human brain after subarachnoid hemorrhage (SAH) and in peritumoral tissue by western blot and immunohistochemistry [1].
• However, data on the effect of proteinuria on the proximal tubule, which is heavily vested with AQP1 and therefore may participate in water homeostasis, are limited [2].
• As an initial step in determining the role of aquaporin (AQP) water channels in myocardial edema, we have assessed the myocardial expression of AQPs in humans, rats, and mice [3].
• Aquaporin-1 expression was found in clear cell renal cell carcinomas and papillary renal cell carcinomas of both types (78 and 73%, respectively), but not in chromophobe renal cell carcinomas, collecting duct carcinomas, and oncocytomas [4].

Psychiatry related information on AQP1

• Significant increased expression levels of AQP1 (as revealed with two different antibodies) and AQP4 were seen in CJD, but not in advanced AD and DLB cases when compared with controls [5].
• Are aquaporin water channels the "holy grail" of primary nocturnal enuresis [6]?
• Here a study is made of how these factors could influence the response of aquaporin to drought. * Methods Three plasma membrane intrinsic proteins (PIPs) or aquaporins were cloned from Phaseolus vulgaris plants and their expression was analysed after 4 d of water deprivation and also 1 d after re-watering [7].

High impact information on AQP1

• The high water permeability characteristic of mammalian red cell membranes is now known to be caused by the protein AQP1 [8].
• AQP1 is distributed in apical and basolateral membranes of renal proximal tubules and descending thin limbs as well as capillary endothelia [8].
• AQP1 is a tetramer with each subunit containing an aqueous pore likened to an hourglass formed by obversely arranged tandem repeats [8].
• Cellular and molecular biology of the aquaporin water channels [8].
• Currently, the best described molecular transporters are the epithelial sodium channel, the cystic fibrosis transmembrane conductance regulator, Na+-K+-ATPase, and several aquaporin water channels [9].

Chemical compound and disease context of AQP1

• A case of a novel mutant vasopressin receptor-dependent nephrogenic diabetes insipidus with bilateral non-obstructive hydronephrosis in a middle aged man: differentiation from aquaporin-dependent nephrogenic diabetes insipidus by response of factor VII and von Willebrand factor to 1-diamino-8-arginine vasopressin administration [10].
• Since glucocorticoid therapy has well known beneficial effects in the treatment of brain edema, the induction of AQP1 by dexamethasone raises a possibility that AQP1 plays a role in ameliorating brain edema [11].
• We report here that aquaporin-1 (AQP1) is specifically induced by retinoic acid (RA) in human erythroleukemia HEL cells [12].
• Acute liver failure results in altered expression of several genes in the brain, some of which code for proteins involved in central nervous system function such as the glutamate transporter GLT-1, the astrocytic structural protein, glial fibrillary acidic protein, and the water channel protein, aquaporin IV [13].

Biological context of AQP1

• Based on these findings, it was possible to convert AQP1 into a cotranslational biogenesis mode similar to that of AQP4 by substituting just two peptide regions at the N terminus of TM2 and the C terminus of TM3 [14].
• Consistent with experimental data, multi-nanosecond molecular dynamics simulations showed one stable binding site for TEA, but not tetramethyl (TMA), in AQP1, resulting in a nearly 50% water permeability inhibition, which was reduced in AQP1-Y186F due to effects on the TEA inhibitory binding region [15].
• Using oocytes, externally applied TEA blocked AQP1/AQP2/AQP4 with IC50 values of 1.4, 6.2, and 9.8 microM, respectively [15].
• Humans are identified with mutations in AQP1 and AQP2 and exhibit contrasting clinical phenotypes [16].
• AQP1 may play a role in water movement from the amniotic cavity across the placenta into the fetal circulation [17].

Anatomical context of AQP1

• Here we report that the AQP1 water channel is specifically localized to glial cells of the peripheral nervous system by immunohistochemistry, RT-PCR, and immunoblotting [18].
• Paraffin-embedded biopsies of human pancreas, esophagus, and sciatic nerves were accessed by immunoperoxidase staining using affinity-purified AQP1, AQP4, and AQP9 antibodies [18].
• Strong AQP1 expression was identified in pancreatic nerve plexuses and in the submucosal and myenteric nerve plexuses in the esophagus [18].
• RT-PCR and immunoblot analysis of microdissected pancreatic ganglia confirmed the expression of AQP1 transcript and protein [18].
• Pancreatic and sciatic nerve bundles, which contain nonmyelinating and myelinating Schwann cells, respectively, were also selectively labeled by AQP1 antibody [18].

Associations of AQP1 with chemical compounds

• Aquaporin-1 (AQP1) is extremely abundant in the proximal tubule and descending thin limb, where it appears to provide the chief route for proximal nephron water reabsorption [19].
• Arrhenius activation energies of water transfer were low when AQP1 or P25 were present in oocyte plasma membranes (Ea = 2.29 and 3.01 kcal/mol, respectively, versus Ea = 11.75 kcal/mol for liposome injected oocytes) [20].
• 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 [21].
• In a recent work, we showed that the aquaporins 1 (AQP1) are permeable to certain small solutes such as glycerol [22].
• On the other hand, AQP1 mRNA expression did not correlate with D/P4 (r=0.21, p=0.2), MTAC of Cr (r=0.05, p=0.7), or with net UF (r=0.17, p=0.3) [23].

Physical interactions of AQP1

• We speculate that CFTR may interact with aquaporin to bring about cytoplasmic volume contraction which is an essential feature of spermiogenesis [24].
• The regulation of AQP1 ion channels could be one of several transport mechanisms that contribute to the decreased CSF secretion in response to endogenous signaling molecules such as atrial natriuretic peptide [25].
• Jk(a-b-) cells have neither Kidd protein nor HUT11 urea transporter and they are characterized by a selective defect of urea transport whereas water transport and aquaporin-1 associated Colton antigens are normally expressed [26].

Co-localisations of AQP1

• We found that CAV-1 is present in thymocytes and that this protein co-localizes with a portion of AQP1 in normal (non-apoptotic) thymocytes [27].
• TRPC1 colocalized with aquaporin-1, a marker for proximal tubule and thin descending limb, but not with aquaporin-2, a marker for connecting tubule and collecting duct cells [28].

Regulatory relationships of AQP1

• AQP1 was localized to the same cell population expressing glial fibrillary acidic protein (GFAP), but not to the neurons in the plexuses, indicating glial cell-specific expression [18].
• Image analysis of normal, OA and RA cartilage suggested that AQP1 may be upregulated in RA [29].
• The perivascular staining around the superficial vessels altered from AQP4 in control retinas to AQP1 in postischemic retinas [30].
• Vasopressin or AVP regulates water reabsorption by the kidney inner medullary collecting duct (IMCD) through the insertion and removal of aquaporin (AQP) 2 water channels into the IMCD apical membrane [31].
• To our knowledge, this is the first demonstration that IFN-alpha regulates the gene expression of an aquaporin [32].

Other interactions of AQP1

• Two aquaporins have been identified so far in the CNS, AQP1 and AQP4 [33].
• To compare the selectivity of AQP-1 and CK7 as possible markers for differentiated cholangiocytes, liver biopsies of cholestatic disease were also analyzed [34].
• Western blot analysis of AQP1 and AQP5 expression in the glands revealed that protein abundance decreased in a similar fashion [35].
• The distribution of the AQP1 and AQP3 proteins was also studied by immunohistochemical staining using affinity-purified polyclonal antibodies [36].
• The vessels in the dermis showed a high incidence of AQP1 and eNOS [37].

Analytical, diagnostic and therapeutic context of AQP1

• Cryoelectron microscopy of reconstituted AQP1 membrane crystals has revealed the three-dimensional structure at 3-6 A [8].
• Immunohistochemistry showed increased AQP1 in astrocytes at early stages of AD [38].
• AQPs 1, 3, 4, 5, 6, and 10 were identified by RT-PCR in developing teeth, and AQP1, 3, 5, and 6 were confirmed by Western blot analysis [39].
• By freeze-fracture electron microscopy, a 20% increase in intramembrane particle (IMP) density was found in plasma membranes of cells expressing AQP2, 3 and 5, and a 100% increase was measured in AQP1-expressing cells, when compared to mock-transfected cells [40].
• Double-labelling immunofluorescence and confocal microscopy disclosed AQP1 immunoreactivity at the cell surface of astrocytes which were recognized with anti-glial fibrillary acidic protein antibodies [38].

References