Evolutionary Overview of Aquaporin Superfamily.

Aquaporins (AQPs) are present not only in three domains of life, bacteria, eukaryotes, and archaea, but also in viruses. With the accumulating arrays of AQP superfamily, the evolutional relationship has attracted much attention with multiple publications on "the genome-wide identification and phylogenetic analysis" of AQP superfamily. A pair of NPA boxes forming a pore is highly conserved throughout the evolution and renders key residues for the classification of AQP superfamily into four groups: AQP1-like, AQP3-like, AQP8-like, and AQP11-like. The complexity of AQP family has mostly been achieved in nematodes and subsequent evolution has been directed toward increasing the number of AQPs through whole-genome duplications (WGDs) to extend the tissue specific expression and regulation. The discovery of the intracellular AQP (iAQP: AQP8-like and AQP11-like) and substrate transports by the plasma membrane AQP (pAQP: AQP1-like and AQP3-like) have accelerated the AQP research much more toward the transport of substrates with complex profiles. This evolutionary overview based on a simple classification of AQPs into four subfamilies will provide putative structural, functional, and localization information and insights into the role of AQP as well as clues to understand the complex diversity of AQP superfamily.

Spinal epidural arteriovenous fistula with improved sphincter impairment detected by intraoperative neurophysiological monitoring.

Background: A spinal epidural arteriovenous fistula (SEAVF) is a rare type of arteriovenous shunt that occurs mainly in the thoracic or lumbar spine. Patients with SEAVF develop motor/sensory disturbances of the lower extremities and sphincter dysfunction. Among these symptoms, sphincter impairments show less improvement than others, and its relevance to neurophysiological monitoring has not been documented. Case Description: A 77-year-old woman presented with progressive motor weakness and numbness in the lower extremities and urinary and fecal incontinence. Spinal magnetic resonance imaging showed spinal cord edema in Th5-Th11 and enlarged perimedullary veins. We performed spinal angiography and endovascular treatment under intraoperative neurophysiological monitoring (IOM), including sensory evoked potential (SEP), motor evoked potential (MEP), and bulbocavernosus reflex (BCR) monitoring. Diagnostic angiography revealed a SEAVF with perimedullary venous drainage fed by the left L2 segmental artery. The shunt was completely embolized using N-butyl-2-cyanoacrylate. Although SEP and MEP of the lower legs were recordable during treatment, anal MEP and BCR were not observed. The sphincter symptoms improved 1.5 years after the treatment. Follow-up angiography revealed no shunt recurrence and improved venous congestion. Anal MEP and BCR were detected during angiography, indicating neurophysiological improvement in sphincter function. The prolonged latency of the monitoring suggested a pudendal nerve injury. Conclusion: This case report first described improvement of the IOM correlated with the functional recovery of sphincters after embolization of a SEAVF. Follow-up neurophysiological monitoring is important to assess the functional recovery of the sphincter.

The role of mammalian superaquaporins inside the cell: An update.

The progress on mammalian superaquaporin (sAQP), AQP11 and AQP12, in the past seven years is brought up to date from the previous review. This subfamily is separated because of the very low homology with other AQP subfamilies and it is present only in multicellular organisms excluding fungi and plants. Its unique intracellular localization, specifically in the ER has made its functional studies challenging, but it may function as glyceroporin, aquaporin and peroxiporin, H2O2 transporter. Knowledge on AQP11 has been expanded by tissue specific conditional knockout mice and by the identification of a SNP associated with kidney diseases. Moreover, the functional identification of AQP11 as a peroxiporin has expanded the role of AQP11 to the regulation of intracellular H2O2 homeostasis to prevent ER stress, which awaits further in vivo studies. As kidney-specific AQP11 knockout of developed kidney has produced little phenotype, AQP11 is critical for kidney development but its physiological significance remains to be clarified. On the other hand, little has been known on pancreas-specific AQP12. To move this field forward, the results of sAQP in lower animals will be necessary to obtain the insights into the role of mammalian sAQP, which hopefully will lead to the discovery of therapeutic targets.

Effects of osmolality on the expression of brain aquaporins in AQP11-null mice.

Water transport in the brain is tightly controlled by blood-brain-barrier (BBB) composed of capillary endothelial cells expressing AQP1/AQP11 and glial foot processes expressing AQP4. Here we examined each AQP mRNA expression in acute hyponatremic and hypernatremic mouse models of wild type (WT) and AQP11 KO mice (KO). The expressions of AQP1, AQP4 and AQP11 mRNAs were quantified by real-time qRT-PCR analysis of whole brain RNA. Acute hyponatremia enhanced AQP4 expression without changing AQP1 expression in KO, whereas it did not change the expression of all AQPs in WT. On the other hand, acute hypernatremia increased AQP4 but decreased AQP1 expression by half in KO, whereas it decreased AQP1 and AQP11 by half without changing AQP4 expression in WT. Enhanced AQP4 expression by osmotic challenges with sodium in KO seems to be a compensation for the loss of AQP11. A stronger hypertonic stimulation with mannitol decreased all AQPs by 30-80% in WT. Since AQP4 plays an important role in the regulation of brain edema at BBB, the results suggest that AQP11 may also be involved in the osmotic regulation of the brain.

Phosphorylation profile of human AQP2 in urinary exosomes by LC-MS/MS phosphoproteomic analysis.

BACKGROUND: Aquaporin-2 (AQP2) is a key water channel protein which determines the water permeability of the collecting duct. Multiple phosphorylation sites are present at the C-terminal of AQP2 including S256 (serine at 256 residue), S261, S264 and S/T269, which are regulated by vasopressin (VP) to modulate AQP2 trafficking. As the dynamics of these phosphorylations have been studied mostly in rodents, little is known about the phosphorylation of human AQP2 which has unique T269 in the place of S269 of rodent AQP2. Because AQP2 is excreted in urinary exosomes, the phosphoprotein profile of human AQP2 can be easily examined through urinary exosomes without any intervention. METHODS: Human urinary exosomes digested with trypsin or glutamyl endopeptidase (Glu-C) were examined by the liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) phosphoproteomic analysis. RESULTS: The most dominant phosphorylated AQP2 peptide identified was S256 phosphorylated form (pS256), followed by pS261 with less pS264 and far less pT269, which was confirmed by the western blot analyses using phosphorylated AQP2-specific antibodies. In a patient lacking circulating VP, administration of a VP analogue showed a transient increase (peak at 30-60 min) in excretion of exosomes with pS261 AQP2. CONCLUSION: These data suggest that all phosphorylation sites of human AQP2 including T269 are phosphorylated and phosphorylations at S256 and S261 may play a dominant role in the urinary exosomal excretion of AQP2.

Perspectives on the evolution of aquaporin superfamily.

Aquaporins (AQPs) belong to a transmembrane protein superfamily composed of an internal repeat of a three membrane-spanning domain and each has a highly conserved NPA box. Based on the more variable carboxyl-terminal NPA box, AQPs can be divided into three subfamilies: (1) glycerol-channel aquaglyceroporin (gAQP) (2) water-selective AQP (wAQP), and (3) deviated superaquaporin (sAQP) in the order of passible evolution. This classification has functional and localization relevance: most wAQPs transports water selectively whereas gAQPs and sAQPs also transport small molecules with sAQPs mostly localized inside the cell. As this classification is not based on the function, some wAQPs functioning as glycerol channels will not be included in gAQPs. AQP ancestors may have first originated in eubacteria as gAQPs to transport small molecules such as glycerol. Later some of them may have acquired a water-selective filter to become wAQPs. Although AQPs are absent in many bacteria, especially in archaea, both gAQPs and wAQPs may have been carried over to eukaryotes or horizontally transferred. Finally, multicellular organisms have obtained new sAQPs, which are curiously absent in fungi and plants. Interestingly, both plants and higher insects independently have lost gAQPs, whose functions, however, have been taken over by functionally modified wAQPs partly obtained by horizontal gene transfers from bacteria. This evolutionary viewpoints on AQPs will facilitate further functional analysis of AQP-like sequences and expand our viewpoints on AQP superfamily.

Proteomic analysis of AQP11-null kidney: Proximal tubular type polycystic kidney disease.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is caused by the mutation of polycystins (PC-1 or PC-2), in which cysts start from the collecting duct to extend to all nephron segments with eventual end stage renal failure. The cyst development is attenuated by a vasopressin V2 receptor antagonist tolvaptan which, however, will not affect proximal tubule cysts devoid of V2 receptor. Aquaporin-11 (AQP11) is expressed selectively in the proximal tubule of the kidney and AQP11-null kidneys have a disruptive PC-1 trafficking to the plasma membrane to develop polycystic kidneys. Here, we analyzed AQP11-null kidneys at the beginning of cyst formation by quantitative proteomic analysis using Tandem Mass Tag (TMT). Among ~ 1200 identified proteins, 124 proteins were differently expressed by > 1.5 or < 0.8 fold change. A pancreatic stone inhibitor or a growth factor, lithostathine-1 (Reg1) was most enhanced by 5 folds which was confirmed by western blot, while mitochondria-related proteins were downregulated. The identified proteins will be new target molecules for the treatment of proximal tubular cysts and helpful to explore the functional roles of AQP11 in the kidney.

The Evolutionary Aspects of Aquaporin Family.

Aquaporins (AQPs ) are a family of transmembrane proteins present in almost all species including virus. They are grossly divided into three subfamilies based on the sequence around a highly conserved pore-forming NPA motif: (1) classical water -selective AQP (CAQP), (2) glycerol -permeable aquaglyceroporin (AQGP) and (3) AQP super-gene channel, superaquaporin (SAQP). AQP is composed of two tandem repeats of conserved three transmembrane domains and a NPA motif. AQP ancestors probably started in prokaryotes by the duplication of half AQP genes to be diversified into CAQPs or AQGPs by evolving a subfamily-specific carboxyl-terminal NPA motif. Both AQP subfamilies may have been carried over to unicellular eukaryotic ancestors, protists and further to multicellular organisms. Although fungus lineage has kept both AQP subfamilies, the plant lineage has lost AQGP after algal ancestors with extensive diversifications of CAQPs into PIP, TIP, SIP, XIP, HIP and LIP with a possible horizontal transfer of NIP from bacteria. Interestingly, the animal lineage has obtained new SAQP subfamily with highly deviated NPA motifs, especially at the amino-terminal halves in both prostomial and deuterostomial animals. The prostomial lineage has lost AQGP after hymenoptera, while the deuterostomial lineage has kept all three subfamilies up to the vertebrate with diversified CAQPs (AQP0, 1, 2, 4, 5, 6, 8) and AQGPs (AQP3, 7, 9, 10) with limited SAQPs (AQP11, 12) in mammals. Whole-genome duplications, local gene duplications and horizontal gene transfers may have produced the AQP diversity with adaptive selections and functional alternations in response to environment changes. With the above evolutionary perspective in mind, the function of each AQP could be speculated by comparison among species to get new insights into physiological roles of AQPs . This evolutionary guidance in AQP research will lead to deeper understandings of water and solute homeostasis.

Quantitative Analysis of Aquaporin Expression Levels during the Development and Maturation of the Inner Ear.

Aquaporins (AQPs) are a family of small membrane proteins that transport water molecules across the plasma membrane along the osmotic gradient. Mammals express 13 subtypes of AQPs, including the recently reported "subcellular AQPs", AQP11 and 12. Each organ expresses specific subsets of AQP subtypes, and in the inner ear, AQPs are essential for the establishment and maintenance of two distinct fluids, endolymph and perilymph. To evaluate the contribution of AQPs during the establishment of inner ear function, we used quantitative reverse transcription polymerase chain reaction to quantify the expression levels of all known AQPs during the entire development and maturation of the inner ear. Using systematic and longitudinal quantification, we found that AQP11 was majorly and constantly expressed in the inner ear, and that the expression levels of several AQPs follow characteristic longitudinal patterns: increasing (Aqp0, 1, and 9), decreasing (Aqp6, 8, and 12), and peak of expression on E18 (Aqp2, 5, and 7). In particular, the expression level of Aqp9 increased by 70-fold during P3-P21. We also performed in situ hybridization of Aqp11, and determined the unique localization of Aqp11 in the outer hair cells. Immunohistochemistry of AQP9 revealed its localization in the supporting cells inside the organ of Corti, and in the root cells. The emergence of AQP9 expression in these cells was during P3-P21, which was coincident with the marked increase of its expression level. Combining these quantification and localization data, we discuss the possible contributions of these AQPs to inner ear function.

Enhanced Autophagy in Polycystic Kidneys of AQP11 Null Mice.

Aquaporin-11 (AQP11) is an intracellular water channel expressed at the endoplasmic reticulum (ER) of the proximal tubule. Its gene disruption in mice leads to intracellular vacuole formation at one week and the subsequent development of polycystic kidneys by three weeks. As the damaged proximal tubular cells with intracellular vacuoles form cysts later, we postulated that autophagy may play a role in the cyst formation and examined autophagy activity before and after cyst development in AQP11(-/-) kidneys. PCR analysis showed the increased expression of the transcript encoding LC3 (Map1lc3b) as well as other autophagy-related genes in AQP11(-/-) mice. Using green fluorescent protein (GFP)-LC3 transgenic mice and AQP11(-/-) mice, we found that the number of GFP-LC3-positive puncta was increased in the proximal tubule of AQP11(-/-) mice before the cyst formation. Interestingly, they were also observed in the cyst-lining epithelial cell. Further PCR analyses revealed the enhanced expression of apoptosis-related and ER stress-related caspase genes before and after the cyst formation, which may cause the enhanced autophagy. These results suggest the involvement of autophagy in the development and maintenance of kidney cysts in AQP11(-/-) mice.

[Newborn Hearing Screening and Subsequent Diagnostic Evaluation: Analysis and Outcomes of 6,063 Infants Born in a Community Hospital].

A retrospective study was conducted to examine the implementation status of newborn hearing screening (NHS) of 6,063 infants born in a single community hospital in Japan between 2005 and 2013. An automated auditory brainstem response device was used for NHS and an auditory brainstem response was mainly used for further diagnostic evaluation. Although the participation rate in the NHS was 88.8% in 2013, increasing year by year, it failed to reach 100% probably because NHS is a charged option under the current Japanese healthcare system. Among 40 (0.66%) infants who finally failed their NHS, 34 were referred for subsequent diagnostic evaluation and the remaining 6 were lost to follow-up. Thirty-one of these 34 were diagnosed as having hearing impairment and 3 (0.05%) were identified as having normal hearing, which is considered as a false positive. Both the final referral rate and the hearing impairment rate were significantly higher in the high-risk than in the low-risk group. Compared to the previous national report, the rate of bilateral hearing impairment (0.33%) was significantly higher in this study. Ten (38.5%) out of 26 in the high-risk group were most often diagnosed with otitis media with effusion (OME), while 4 (50%) out of 8 in the low-risk group were diagnosed as having sensorineural hearing loss. Seven (35%) out of 20 with bilateral hearing impairment attained a normal hearing level at a median age of 18 months. Although the primary aim of NHS is early detection of congenital permanent hearing loss, OME is observed commonly in NHS-failed infants. It is therefore important to examine the middle ear status carefully as part of the diagnostic evaluation. Thirty-four infants underwent further diagnostic evaluation at a median age of 46 days, and hearing aids were given in 10 of them at a median age of 5.6 months without delay. Because high-risk patients often tend to be lost to follow-up, otolaryngologists have to give a detailed explanation to caregivers and to build a solid support system for children with hearing impairment.

Aquaporin-11 (AQP11) Expression in the Mouse Brain.

Aquaporin-11 (AQP11) is an intracellular aquaporin expressed in various tissues, including brain tissues in mammals. While AQP11-deficient mice have developed fatal polycystic kidneys at one month old, the role of AQP11 in the brain was not well appreciated. In this study, we examined the AQP11 expression in the mouse brain and the brain phenotype of AQP11-deficient mice. AQP11 messenger ribonucleic acid (mRNA) and protein were expressed in the brain, but much less than in the thymus and kidney. Immunostaining showed that AQP11 was localized at the epithelium of the choroid plexus and at the endothelium of the brain capillary, suggesting that AQP11 may be involved in water transport at the choroid plexus and blood-brain barrier (BBB) in the brain. The expression of AQP4, another brain AQP expressed at the BBB, was decreased by half in AQP11-deficient mice, thereby suggesting the presence of the interaction between AQP11 and AQP4. The brain of AQP11-deficient mice, however, did not show any morphological abnormalities and the function of the BBB was intact. Our findings provide a novel insight into a water transport mechanism mediated by AQPs in the brain, which may lead to a new therapy for brain edema.

Aquaporin10 is a pseudogene in cattle and their relatives.

BACKGROUND: Although AQP10 is mainly expressed in the human GI tract, its physiological role is unclear. In fact, we previously reported that mouse AQP10 is a pseudogene. It is possible that AQP10 is also a pseudogene in other animals. METHODS: Genome databases were searched for AQP10 orthologs and the genomic DNA of each candidate pseudogene was sequenced to confirm its mutations. The expression of the AQP10 mRNA was examined by RT-PCR in the small intestine where human AQP10 is highly expressed. RESULTS: The genomic database of some mammals had insertions and deletions in the exons of the AQP10 gene, including cattle (Bos taurus), sheep (Ovis aries) and goats (Capra hircus). In the bovine AQP10 gene, exon 1 and 5 had deletions resulting in a frame-shift or a premature termination, respectively, which were confirmed by the direct exon sequencing of the genomic DNA. In the RT-PCR experiments, the PCR primer sets for exon 1/2 and exon 4/5 failed to detect the bands for AQP10 mRNA in the duodenum and jejunum. Similar AQP10 gene mutations were also confirmed in the genomic DNA from sheep and goats. Although these animals were derived from porcine ancestors, the exons of the swine (Sus scrofa) AQP10 gene were complete without mutations. Therefore, AQP10 gene might have turned to a pseudogene around 65 million years before when cattle evolved from porcine ancestors. CONCLUSION: AQP10 of ruminantia which regurgitate and rechew their food may have lost its role possibly due to the redundant expression of other aquaglyceroporins.

[The accuracy of evaluating the response of metastatic lymph nodes after concurrent chemoradiotherapy in patients with head and neck squamous cell carcinoma].

BACKGROUND: Concurrent chemoradiotherapy (CCRT) is used to treat advanced head and neck cancer. The accuracy of evaluating lymph nodes metastases following CCRT is important for subsequent therapy. PATIENTS AND METHODS: Patients were divided into two groups according to the nodal status, the complete response (CR) and the non-CR groups, as determined by imaging and fine-needle aspiration cytology (FNAC) performed 4-8 weeks after the CCRT, and the findings were compared with the status 6 months after the treatment completion. RESULTS: The sensitivity, the specificity, positive predictive value, negative predictive value and accuracy of each evaluation method were as follows: 66.7%, 73.5%, 26.7%, 93.8% and 72.5%, respectively, for computer tomography (CT) and magnetic resonance imaging (MRI); 91.7%, 69.9%, 30.6%, 98.3% and 72.6% for ultrasonography (US) ; 50.0%, 96.4%, 66.7%, 93.0% and 90.5% for fluorodeoxyglucose-positron emission tomography (FDG-PET) or PET-CT; and 68.4%, 96.1%, 81.3%, 92.5% and 90.6% for FNAC. CONCLUSION: To evaluate the response of lymph node(s) treated by CCRT, US is useful as a positive screening tool and FDG-PET and PET-CT as negative screening tools. FNAC is useful in evaluating suspicious lymph nodes in both positive and negative cases.

The role of mammalian superaquaporins inside the cell.

BACKGROUND: The mammalian two superaquaporins, AQP11 and AQP12, are present inside the cell and their null phenotypes in mice suggest their unusual functions. SCOPE OF REVIEW: The surveyed literature on these superaquaporins and our unpublished data has been incorporated to speculate their roles. MAJOR CONCLUSIONS: AQP11 and AQP12 have unique NPA boxes with a signature cysteine residue. Although some water permeability of AQP11 was demonstrated in liposomes and cultured cells, its permeability to glycerol is unknown. The function of AQP12 still remains to be clarified. AQP11 null mice develop polycystic kidneys following large intracellular vacuoles in the proximal tubule, which may be caused by ER stress or vesicle fusion failure. The role of AQP11 in the kidney and liver seems to alleviate the tissue damage and facilitate the recovery. Its expression in the sperm, thymus and brain suggests its potential roles in these organs in spite of the apparently normal null phenotype. Although AQP12 null mice appear normal, they suffer from severe pancreatitis, suggesting its role in the fusion of zymogen granules. GENERAL SIGNIFICANCE: As many issues are unsolved, the clarification of the function and roles of the superaquaporin may lead to the identification of new roles of AQPs. This article is part of a Special Issue entitled Aquaporins.

A case of apoplectic lymphocytic hypophysitis complicated by polymyalgia rheumatica.

A case of apoplectic lymphocytic hypophysitis complicated by polymyalgia rheumatica (PMA) is described. A 72-year-old man was admitted to our hospital due to severe headache. Two months prior to admission, the patients had exhibited recent-onset stiffness and myalgia of shoulder and pelvic girdle that was compatible with PMR. Magnetic resonance imaging revealed a mass lesion in the pituitary fossa with focal hemorrhage. Endocrinologic studies demonstrated hypopituitarism. The headache and myalgia were improving with corticosteroid treatment; however, a trans-sphenoidal surgery was performed due to visual field loss. A white-colored mass was resected, and histologic examination showed diffuse infiltration of lymphocytes and plasma cells consistent with lymphocytic hypophysitis. Post-operatively, the headache and visual field loss resolved completely. This is the first documented case of apoplectic lymphocytic hypophysitis complicating PMR, and a possible mechanism for this rare association was discussed.

Molecular cable-like 1-D iodic spiral chains covered with triple helices stabilized in guest-included chiral porous framework.

The supramolecular crystal {[Pr(DMFA)](3)[Ni(II)(Hbim)(3)](2)I}(n) with intricate chiral networks of [Ni(II)(Hbim)(3)](-) molecules is reported. It includes a cationic architecture as a guest, constructed from chiral nanotubes that penetrate I(-) chains with spiral channels wrapped by triple helices. The I(-) chains have AC conductivity in crystals like a molecular cable.

Brominated thiophenes as precursors in the preparation of brominated and arylated anthraquinones.

Brominated anthraquinones can be synthesized directly from bromothiophenes when these are reacted with 1,4-naphthoquinones in the presence of meta-chloroperoxybenzoic acid. The bromoanthraquinones are versatile building blocks in the preparation of arylated anthraquinones and of extended pi-systems with interspersed anthraquinone units.

The role of a group III AQP, AQP11 in intracellular organelle homeostasis.

AQP11 is a member of a new aquaporin subfamily which includes many aquaporin homologs with low amino acid identities, around 20% of previously identified AQPs. Although these AQPs have unusual NPA sequences, these AQPs have a completely conserved and functionally indispensable cysteine residue downstream of the second NPA box, suggesting that they belong to a specific AQP subfamily, which we propose to name the group III AQPs. On the other hand, the NPA boxes are highly conserved in previous AQP subfamilies: the group I AQPs, original water-selective aquaporin family and the group II AQPs, aquaglyceroporin family. Currently the roles of the group III AQPs are only known with AQP11 as the disruption of intracellularly located AQP11 in mice produced huge vacuoles in the proximal tubule leading to fatal polycystic kidneys at one month old. This review focused on the classification of AQPs based on primary structures to obtain insights into the function and the role of AQPs. With the accumulation of new AQP-like sequences through genome projects, this classification will be useful to predict their functions as each group may have specific characteristics in its function, distribution and regulation.

Aquaporin-11 knockout mice and polycystic kidney disease animals share a common mechanism of cyst formation.

Aquaporin-11 (AQP11), a new member of the aquaporin family, is localized in the endoplasmic reticulum (ER). Aqp11(-/-) mice neonatally suffer from polycystic kidneys derived from the proximal tubule. Its onset is proceeded by the vacuolization of ER. However, the mechanism for the formation of vacuoles and cysts remains to be clarified. Here, we show that Aqp11(-/-) mice and polycystic kidney disease (PKD) animals share a common pathogenic mechanism of cyst formation. We performed microarray analyses and histochemical staining to characterize the effects of the disruption of Aqp11 on kidneys of 1-wk-old mice. Microarray analyses revealed that the significantly changed functional categories in Aqp11(-/-) mice were similar to those in PKD animals. Histochemical studies showed expression changes of 3 genes, Myc, Egfr, Egf, which are assumed to be involved in the proliferation of cystic cells in PKD. We actually confirmed the activation of cell proliferation in the proximal tubule cells with vacuolized ER. Furthermore, three genes associated with the remodeling of the extracellular matrix, Mmp12, Timp1, Tgfb1, were up-regulated in the fibroblasts. We also demonstrated the activation of apoptosis via the ER-stress pathway in the proximal tubule cells with vacuolized ER. These results provide new insights into the physiological roles of AQP11.