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Phylogenetic tree of mammalian aquaporins and E. coli homologs. Note the genetic and functional groupings into aquaporins, selective for water (bottom) or aquaglyceroporins, permeated by water and glycerol (top). MIP denotes major intrinsic protein of lens. Generated using ClustalW software (53).
Contexts in source publication
Context 1
... duct epithelium, but lack of AQP1 at this site predicted the existence of additional aquaporins (5). Homology cloning by polymerase chain amplification using degenerate oligonucleotide primers has been employed by multiple investigators to clone aquaporin homologs. Efforts have rapidly led to the recognition of at least 10 mammalian aquaporins (Fig. 4). All members of the family contain structural motifs similar to AQP1, but each probably has special features needed for function or ...
Context 2
... of sequences and functional properties showed that this protein family is comprised of two subgroups (18): water- selective homologs (aquaporins) and other homologs that are per- meated by water, glycerol, and other small molecules (aquaglycero- porins) (Fig. ...
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... is also expressed in multiple other tissues includ- ing airways and is particularly abundant in nasopharyngeal epi- thelium, where roles in mucosal secretions and allergic rhinitis are suspected (32). Multiple other aquaglyceroporins are now being identified by cDNA cloning and computer search of expressed sequence tagged (EST) cDNA libraries (Fig. 4). A cDNA encoding AQP7 was isolated from rat testis (38). AQP7 may provide a port for water and glycerol as a carbon source and may permit replacement of water by glyc- erol during cryopreservation of sperm. At the same time, AQP7L, a highly related cDNA, was isolated from human adipose tissue (39), which may facilitate glycerol export ...
Context 4
... water and glycerol as a carbon source and may permit replacement of water by glyc- erol during cryopreservation of sperm. At the same time, AQP7L, a highly related cDNA, was isolated from human adipose tissue (39), which may facilitate glycerol export during lipolysis. Preliminary evidence supports the existence of another homolog designated AQP9 (Fig. ...
Context 5
... has been shown to transport glycerol by a porelike mechanism. AqpZ, like mamma- lian and plant aquaporins, is a selective water channel, and AqpZ is operative during rapid growth (48). The importance of the aqua- porin-aquaglyceroporin dualism is being explored in E. coli and may provide insight into their presence in higher organisms (Fig. 4). As microbial genomes become sequenced, multiple aquaporin homologs are becoming recognized. The Saccharomyces genome contains two open reading frames related to aquaglyceroporins and two others related to aquaporins (49). The slime mold Dictyoste- lium discoideum expresses an aquaporin-like protein in prespore cells (50). The ...
Citations
... Since their discovery, our knowledge of aquaporins (AQPs) reveals the intricate regulation and diverse functions governing their interactions. Agre described them as the cell's plumbing system [1], yet their role and function in the cell are far from being as straightforward. Today, we understand the mechanism governing water transport, which is highly specific for water molecules due to the selectivity filter within the pore [2]. ...
Triple-negative breast cancer (TNBC) remains one of the most challenging subtypes since it is initially characterized by the absence of specific biomarkers and corresponding targeted therapies. Advances in methodology, translational informatics, genomics, and proteomics have significantly contributed to the identification of therapeutic targets. The development of innovative treatments, such as antibody–drug conjugates and immune checkpoint inhibitors, alongside chemotherapy, has now become the standard of care. However, the quest for biomarkers defining therapy outcomes is still ongoing. Peroxiporins, which comprise a subgroup of aquaporins, which are membrane pores facilitating the transport of water, glycerol, and hydrogen peroxide, have emerged as potential biomarkers for therapy response. Research on peroxiporins reveals their involvement beyond traditional channeling activities, which is also reflected in their cellular localization and roles in cellular signaling pathways. This research on peroxiporins provides fresh insights into the mechanisms of therapy resistance in tumors, offering potential avenues for predicting treatment outcomes and tailoring successful TNBC therapies.
... Aquaporins were rst reported by Denker et al. (1988) and puri ed a large amount of a 28 kDa protein from human erythrocyte membranes. AQPs are widely expressed throughout the body, especially in cell types engaged in uid transport and a few other cell types that may not be directly involved (Agre et al. 1998;Zhu et al. 2016). AQPs are intrinsic membrane proteins that function as selective channels for water and solutes like glycerol and urea (Hohmann et al. 2000). ...
A lack of adequate quality and quantity of water impacts goat physiology. Goats may adapt in harsh climatic conditions lacking water by changing their expression of aquaporin (AQP) genes for effective water absorption. The present study aimed to study the seasonal mRNA expression of aquaporins (AQP1, AQP2 and AQP3) in the renal system of goat ( Capra hircus ) concerning their thermoregulation. Tissue samples of the renal cortex, renal medulla, ureter and urinary bladder of 10 male goats aged two years were collected from the slaughterhouse at Karnal, Haryana each during the summer (hot), spring (thermoneutral) and winter (cold) seasons and analyzed for gene expression by real time-polymerized chain reactions and their immunolocalization. The physiological responses of the animals were recorded before slaughtering of experimental animals. The study confirmed the mRNA expression and immunohistolocalization of AQP1, AQP2 and AQP3 in the renal system of goats. AQP1 was found to be higher in the cortex of the renal system during summer in comparison to winter. The relative expressions of AQP2 and AQP3 were higher in the renal medulla than in the renal cortex during the summer. The seasonal variations in AQP1 mRNA expression was found non-significant in ureter of goats, but significantly (p < 0.05) higher during summer comparison to winter in urinary bladder of goat. The relative expression of AQP2 and AQP3 were found to be upregulated in both ureter and urinary bladder tissue sample during summer. The relative mRNA expression of AQP3 was found to be significantly (p < 0.05) higher in ureter and urinary bladder as compared to AQP1 and AQP2 during summer season. The fluctuations in aquaporins gene expression during water stress and hyperosmotic conditions of renal cells suggest the aquaporins genes’ beneficial participation in preserving the body's water balance.Variations in the serumhormone assay components were observed in the goats during the summer seasons. The significant (p < 0.05) increase in the aldosterone (ALD) andvasopressin/anti-diuretic hormone (ADH) concentrations was high during summer, showing a direct relationship with efficient water balancing mechanisms in the body of goat during different seasons in tropical climatic conditions.
... Cells physiologically undergo constant volume fluctuations, in the form of cell swelling or cell shrinking, depending on whether they occur under hypoosmotic or hyperosmotic conditions, respectively (Feher, 2012;Dmitriev et al., 2019). Although this process is primarily due to the simple diffusion of water molecules across plasma membranes, the speed of cell swelling and shrinkage is significantly increased by the expression of the water channels aquaporins (AQPs) that facilitate osmotic water flows, bidirectionally (Agre et al., 1998;Jin et al., 2011). Considering the osmotic water permeability coefficient (Pf ) as an accurate parameter to define water transport properties of a defined barrier, the expression of AQPs significantly increases water membrane permeability of a cell (Pf > 0.01 cm/s) compared to simple diffusion of water molecules (Pf < 0.005 cm/s) (Verkman, 2000). ...
Despite of the major role of aquaporin (AQP) water channels in controlling transmembrane water fluxes, alternative ways for modulating water permeation have been proposed. In the Central Nervous System (CNS), Aquaporin-4 (AQP4) is reported to be functionally coupled with the calcium-channel Transient-Receptor Potential Vanilloid member-4 (TRPV4), which is controversially involved in cell volume regulation mechanisms and water transport dynamics. The present work aims to investigate the selective role of TRPV4 in regulating plasma membrane water permeability in an AQP4-independent way. Fluorescence-quenching water transport experiments in Aqp4–/– astrocytes revealed that cell swelling rate is significantly increased upon TRPV4 activation and in the absence of AQP4. The biophysical properties of TRPV4-dependent water transport were therefore assessed using the HEK-293 cell model. Calcein quenching experiments showed that chemical and thermal activation of TRPV4 overexpressed in HEK-293 cells leads to faster swelling kinetics. Stopped-flow light scattering water transport assay was used to measure the osmotic permeability coefficient (Pf, cm/s) and activation energy (Ea, kcal/mol) conferred by TRPV4. Results provided evidence that although the Pf measured upon TRPV4 activation is lower than the one obtained in AQP4-overexpressing cells (Pf of AQP4 = 0.01667 ± 0.0007; Pf of TRPV4 = 0.002261 ± 0.0004; Pf of TRPV4 + 4αPDD = 0.007985 ± 0.0006; Pf of WT = 0.002249 ± 0.0002), along with activation energy values (Ea of AQP4 = 0.86 ± 0.0006; Ea of TRPV4 + 4αPDD = 2.73 ± 1.9; Ea of WT = 8.532 ± 0.4), these parameters were compatible with a facilitated pathway for water movement rather than simple diffusion. The possibility to tune plasma membrane water permeability more finely through TRPV4 might represent a protective mechanism in cells constantly facing severe osmotic challenges to avoid the potential deleterious effects of the rapid cell swelling occurring via AQP channels.
... AQPs are a family of homologous water channel proteins with molecular weights ranging between 25 and 34 kDa that provide a major route for osmotically driven water movement across the plasma membrane in various cell types. To date, at least 13 distinct subtypes of AQPs (AQPs 0-12) have been identified, which are functionally subdivided into orthodox AQPs (AQP0, 1, 2, 4, 5, 6, and 8, which are primarily water selective), aquaglyceroporins (AQP3, 7, 9 and 10, which are permeable to water and neutral solutes such as glycerol and urea) and superaquaporins (AQP11 and 12, for which details of their localization and functions remain undetermined) [12,13]. Another subclass of the AQP family, the peroxiporins (AQP1, 3, 5, 8, 9, and 11, which are permeable to hydrogen peroxide), has been recognized in recent years [14,15]. ...
Background: Exposure to arsenic (As) or p‑phenylenediamine (PPD) can lead to dysfunction, or even cancer, in various types of organs, including the urinary bladder, yet the underlying mechanisms remain unclear. Aquaporins (AQPs) are widely expressed small water channel proteins that provide the major route for the transport of water and other small molecules across plasma membranes in diverse cell types. Altered expression of AQPs has been associated with pathologies in all major organs, including the urinary bladder.
Objective: The present in vitro study was performed as a first step towards exploring the possible involvement of AQPs in As- and PPD‑induced bladder diseases.
Methods: An immortalized normal human urothelial cell line was employed. Cells were exposed to different concentrations of sodium arsenate (0‑20 μM) or PPD (0‑200 μM) for 48 h. Cell viability was subsequently assessed. The mRNA and protein expression levels of AQPs (specifically, AQP3, 4, 7, 9, and 11) were analyzed using reverse transcription‑quantitative polymerase chain reaction and Western blot analyses, respectively.
Results: The viability of the cells was decreased in a concentration-dependent manner upon exposure to arsenate. The mRNA and protein expression levels of AQP3, 4, 7, and 9 were substantially reduced, whereas the expression of AQP11 was largely unchanged. As for the experiments with PPD, treatment with increasing concentrations of PPD induced a gradual decrease in cell viability. The mRNA and protein expression levels of AQP3, 4, and 11 were generally unaltered; however, a marked reduction in the expression levels of AQP7 was observed, contrasting with a gradual concentration-dependent decrease in the expression of AQP9.
Conclusion: The importance of the differential expression profiles of the AQPs induced by arsenate and PPD requires further investigation; nevertheless, the findings of the present study suggest that AQPs have a role in As‑ and PPD‑induced bladder diseases.
... Aquaporins (AQPs), which are present in multiple mammalian tissues, invertebrates, plants, and microbes [27], serve as channels transferring water and, in some cases, small solutes across membranes [28]. Until now, 13 members of the AQP family have been identified in mammalian cells, of which AQP1, AQP4, and AQP9 are present in the central nervous system (CNS) [29]. ...
Cognitive impairment refers to notable declines in cognitive abilities including memory, language, and emotional stability leading to the inability to accomplish essential activities of daily living. Astrocytes play an important role in cognitive function, and homeostasis of the astrocyte-neuron lactate shuttle (ANLS) system is essential for maintaining cognitive functions. Aquaporin-4 (AQP-4) is a water channel expressed in astrocytes and has been shown to be associated with various brain disorders, but the direct relationship between learning, memory, and AQP-4 is unclear. We examined the relationship between AQP-4 and cognitive functions related to learning and memory. Mice with genetic deletion of AQP-4 showed significant behavioral and emotional changes including hyperactivity and instability, and impaired cognitive functions such as spatial learning and memory retention. ¹⁸ F-FDG PET imaging showed significant metabolic changes in the brains of AQP-4 knockout mice such as reductions in glucose absorption. Such metabolic changes in the brain seemed to be the direct results of changes in the expression of metabolite transporters, as the mRNA levels of multiple glucose and lactate transporters in astrocytes and neurons were significantly decreased in the cortex and hippocampus of AQP-4 knockout mice. Indeed, AQP-4 knockout mice showed significantly higher accumulation of both glucose and lactate in their brains compared with wild-type mice. Our results show that the deficiency of AQP-4 can cause problems in the metabolic function of astrocytes and lead to cognitive impairment, and that the deficiency of AQP4 in astrocyte endfeet can cause abnormalities in the ANLS system.
... In aquaporins that exclusively transport water, the ar/R region contains a Phe residue from TM2, a His residue from TM5 and two residues from Loop E: one small residue that provides a backbone carbonyl oxygen, usually Cys, Thr or Ala, and an Arg that is highly conserved in both water-transporting aquaporins as well as aquaglyceroporins (Figure 1). In the aquaglyceroporins, the Phe from TM2 is replaced by a Trp residue, the His from TM5 is replaced by a Gly residue and the small residue from Loop E is replaced by a Phe, giving rise to a wider selectivity filter [102,[164][165][166][167]. ...
Aquaporins (AQPs) are small transmembrane tetrameric proteins that facilitate water, so-lute and gas exchange. Their presence has been extensively reported in the biological membranes of almost all living organisms. Although their discovery is much more recent than ion transport systems , different biophysical approaches have contributed to confirm that permeation through each monomer is consistent with closed and open states, introducing the term gating mechanism into the field. The study of AQPs in their native membrane or overexpressed in heterologous systems have experimentally demonstrated that water membrane permeability can be reversibly modified in response to specific modulators. For some regulation mechanisms, such as pH changes, evidence for gating is also supported by high-resolution structures of the water channel in different configurations as well as molecular dynamics simulation. Both experimental and simulation approaches sustain that the rearrangement of conserved residues contributes to occlude the cavity of the channel restricting water permeation. Interestingly, specific charged and conserved residues are present in the environment of the pore and, thus, the tetrameric structure can be subjected to alter the positions of these charges to sustain gating. Thus, is it possible to explore whether the displacement of these charges (gating current) leads to conformational changes? To our knowledge, this question has not yet been addressed at all. In this review, we intend to analyze the suitability of this proposal for the first time.
... 23 Being able to measure water exchange can help understanding some of its mechanisms governed primarily by molecule diffusivity across the plasma membrane and transport via aquaporins. 40 Moreover, it was shown that cancer cells with increased metabolic activity can be associated with higher water exchange rates compared with normal tissues. 22 Here, we examine the use of KM for measuring water exchange time in head and neck cancer without an exogenous contrast agent. ...
Purpose
To assess the reliability of measuring diffusivity, diffusional kurtosis, and cellular‐interstitial water exchange time with long diffusion times (100–800 ms) using stimulated‐echo DWI.
Methods
Time‐dependent diffusion MRI was tested on two well‐established diffusion phantoms and in 5 patients with head and neck cancer. Measurements were conducted using an in‐house diffusion‐weighted STEAM‐EPI pulse sequence with multiple diffusion times at a fixed TE on three scanners. We used the weighted linear least‐squares fit method to estimate time‐dependent diffusivity, D(t)$$ D(t) $$, and diffusional kurtosis, K(t)$$ K(t) $$. Additionally, the Kärger model was used to estimate cellular‐interstitial water exchange time (τex$$ {\tau}_{ex} $$) from K(t)$$ K(t) $$.
Results
Diffusivity measured by time‐dependent STEAM‐EPI measurements and commercial SE‐EPI showed comparable results with R² above 0.98 and overall 5.4 ± 3.0% deviation across diffusion times. Diffusional kurtosis phantom data showed expected patterns: constant D$$ D $$ and K$$ K $$ = 0 for negative controls and slow varying D$$ D $$ and K$$ K $$ for samples made of nanoscopic vesicles. Time‐dependent diffusion MRI in patients with head and neck cancer found that the Kärger model could be considered valid in 72% ± 23% of the voxels in the metastatic lymph nodes. The median cellular‐interstitial water exchange time estimated for lesions was between 58.5 ms and 70.6 ms.
Conclusions
Based on two well‐established diffusion phantoms, we found that time‐dependent diffusion MRI measurements can provide stable diffusion and kurtosis values over a wide range of diffusion times and across multiple MRI systems. Moreover, estimation of cellular‐interstitial water exchange time can be achieved using the Kärger model for the metastatic lymph nodes in patients with head and neck cancer.
... They have been applied only for a decade, to manufacture highly efficient and sustainable water filtration membranes (176). Aquaporins, the transmembrane water channel proteins have been selectively transporting water molecules across the cells of living organisms for a billion years (177). Several water purification membranes have been synthesized with Aquaporin incorporation in them following deciphering aquaporin protein structure by Peter Agre in the early 1990s for which he was awarded the Nobel prize (178). ...
Water is essential for human survival. Hence, universal access to safe and affordable drinking water is included as one of the Sustainable Development Goals of the United Nations. With increasing global water stress and stricter revised regulations by bodies such as World Health Organization (WHO) and U.S. Environmental Protection Agency (USEPA) for safe drinking water, it is imperative to research efficient water treatment and quality monitoring technologies that are environmentally benign, affordable, and have ease of implementation. In this regard, sustainable nanomaterial-based technologies are capable of delivering real-time solutions cost-effectively using less energy by reducing ecological impact. These technologies are expected to play a significant role in water remediation including potable water treatment, sensing, wastewater desalination, and water harvesting. However, it is crucial to carefully assess the various sustainability criteria for diverse technologies before their large-scale implementation. In this chapter, we discuss a variety of emerging nanomaterial-based treatment and sensing techniques in the scientific literature and in the market, from the concepts of sustainability and their applications to assess clean water technologies using sustainability metrics. Bio-based processes look promising for the future of water purification in terms of effectiveness and environmental safety. Apart from current nanotechnological frontiers in diverse clean water applications, suggestions for future research are also provided.
... These processes generate the osmotic gradient that powers the mass flow of water into the MT lumens both by paracellular movement and transcellular transport through aquaporins (AQPs) in SCs [7,12,13,[20][21][22]. Aquaporins (AQPs) are six transmembrane-domain proteins that facilitate the transport of water and small solutes across the cell membrane and are responsible for a large portion of the water excretion mediated by MTs [10,[23][24][25]. ...
Malpighian tubules, the renal organs of mosquitoes, facilitate the rapid dehydration of blood meals through aquaporin-mediated osmosis. We performed phosphoproteomics analysis of three Malpighian tubule protein-libraries (1000 tubules/sample) from unfed female mosquitoes as well as one and 24 hours after a blood meal. We identified 4663 putative phosphorylation sites in 1955 different proteins. Our exploratory dataset reveals blood meal-induced changes in phosphorylation patterns in many subunits of V-ATPase, proteins of the target of rapamycin signaling pathway, vesicle-mediated protein transport proteins, proteins involved in monocarboxylate transport, and aquaporins. Our phosphoproteomics data suggest the involvement of a variety of new pathways including nutrient-signaling, membrane protein shuttling, and paracellular water flow in the regulation of urine excretion. Our results support a model in which aquaporin channels translocate from intracellular vesicles to the cell membrane of stellate cells and the brush border membrane of principal cells upon blood feeding.
... Among these pathways, transcellular water transport in plants is facilitated by a class of integral membrane protein known as aquaporins (AQPs). These are pore-forming transmembrane protein predominantly present in almost all living organisms, including animals, plants, and microbes (Agre et al., 1998;Deshmukh et al., 2017;Quigley et al., 2001). They play a vital role in the transport of water and many other small molecules like silica acid, urea, ammonia, and carbon dioxide (Deshmukh and Bélanger, 2016b;Kitchen et al., 2015;Kreida and Toernroth-Horsefield, 2015). ...
Understanding of aquaporins (AQPs) facilitating the transport of water and many other small solutes including metalloids like silicon (Si) and arsenic (As) is important to develop stress tolerant cultivars. In the present study, 40 AQPs were identified in the genome of pigeonpea (Cajanus cajan), a pulse crop widely grown in semi-arid region and areas known to affected with heavy metals like As. Conserved domains, variation at NPA motifs, aromatic/arginine (ar/R) selectivity filters, and pore morphology defined here will be crucial in predicting solute specificity of pigeonpea AQPs. The study identified CcNIP2-1 as an AQP predicted to transporter Si (beneficial element) as well as As (hazardous element). Further Si quantification in different tissues showed about 1.66% Si in leaves which confirmed the predictions. Furthermore, scanning electron microscopy showed a higher level of Si accumulation in trichomes on the leaf surface. A significant alleviation in level of As, Sb and Ge stress was also observed when these heavy metals were supplemented with Si. Estimation of relative water content, H2O2, lipid peroxidation, proline, total chlorophyll content and other physiological parameters suggested Si derived stress tolerance. Extensive transcriptome profiling under different developmental stages from germination to senescence was performed to understand the tissue-specific regulation of different AQPs. For instance, high expression of TIP3s was observed only in reproductive tissues. Co-expression network developed using transcriptome data from 30 different conditions and tissues, showed interdependency of AQPs. Expression profiling of pigeonpea performed using real time PCR showed differential expression of AQPs after Si supplementation. The information generated about the phylogeny, distribution, molecular evolution, solute specificity, and gene expression dynamics in article will be helpful to better understand the AQP transport system in pigeonpea and other legumes.
