Molecular Cloning and Expression of a Novel Human Aquaporin from Adipose Tissue with Glycerol Permeability

Kuriyama, Hiroshi; Kawamoto, Shoko; Ishida, Narihiro; Ohno, Ikko; Mita, Shiro; Matsuzawa, Yūji; Matsubara, Kazuo; Okubo, Kousaku

doi:10.1006/bbrc.1997.7769

Cited by 165 publications

(104 citation statements)

References 21 publications

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“…However, the molecule(s) responsible for the effective transport of glycerol has not been identified. We postulated that AQP7 acts as the adipose glycerol channel because AQP7 is glycerolpermeable and is expressed abundantly in adipose tissue (11,12). In this regard, epinephrine-stimulated glycerol release from 3T3-L1 adipocytes and plasma glycerol concentrations in rodents increased in parallel with the induction of Aqp7 mRNA in the cells and adipose tissue, respectively.…”

Section: Discussionmentioning

confidence: 99%

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Adaptation to fasting by glycerol transport through aquaporin 7 in adipose tissue

Maeda

Funahashi

Hibuse

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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165

134

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Adipocytes hydrolyze triglycerides and secrete free fatty acids and glycerol into the circulation. The molecular mechanism involved in glycerol transport from adipocytes has not been elucidated. Here, we investigated glycerol and glucose metabolism in mice lacking aquaporin 7 (Aqp7), a member of the aquaglyceroporins expressed in adipose tissue, and demonstrated that Aqp7 functions as a glycerol gateway molecule in vivo. Aqp7-knockout (KO) mice had lower plasma glycerol levels compared with WT mice but had normal plasma free fatty acid levels. The increase in plasma glycerol level in response to ␤3-adrenergic agonist was severely impaired in KO mice. Epinephrine-stimulated glycerol secretion was also impaired in Aqp7 knockdown adipocytes. During prolonged fasting, plasma glycerol was elevated and the plasma glucose level was maintained in WT mice. In contrast, KO mice showed a disrupted increase of plasma glycerol and rapid reduction of plasma glucose during prolonged fasting. Our findings indicate that the lack of effective glycerol transport from adipocytes by glycerol gateway molecule causes defective adaptation to prolonged fasting.adipocyte ͉ gluconeogenesis ͉ lipolysis ͉ knockout mice

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Section: Discussionmentioning

confidence: 99%

“…Some of AQPs are known to permeabilize glycerol as well as water (9,10) and are subcategorized as aquaglyceroporins. We previously cloned a cDNA belonging to aquaglyceroporin from a human adipose tissue cDNA library, designated as AQP adipose (AQPap) (11)(12)(13)(14)(15). Subsequently, other groups demonstrated that AQPap was a human homologue of Aqp7.…”

mentioning

confidence: 99%

Adaptation to fasting by glycerol transport through aquaporin 7 in adipose tissue

Maeda

Funahashi

Hibuse

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

165

134

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“…AQP7 may provide a port for water and glycerol as a carbon source and may permit replacement of water by glycerol 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.…”

Section: Minireview: Aquaporins Blueprints For Cellular Plumbing Sysmentioning

confidence: 99%

The Aquaporins, Blueprints for Cellular Plumbing Systems

Agre

Bonhivers²,

Borgnia³

1998

Journal of Biological Chemistry

426

281

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Membrane Water PermeabilityPlasma membranes provide an effective barrier to the extracellular environment. Water was long believed to move through lipid bilayers by simple diffusion; however, membranes from different tissues vary in their permeability to water. The variability is particularly evident in mammalian kidney where proximal tubules and descending thin limbs of Henle's loop have constitutively high water permeability and are responsible for reabsorption of more than 150 liters per day in adult humans. In contrast, ascending thin limbs have very low water permeability. Renal distal tubules empty into collecting ducts where stimulation with vasopressin causes an increase in water permeability (see Ref. 1 for review). These observations led to the suggestion that specialized water transport molecules must exist in membranes with intrinsically high water permeability. Nevertheless, despite extensive studies, the molecular identity of water transport proteins remained elusive until recently.The well defined features of membrane water permeability permitted serendipitous identification of the first known water channel. While purifying the 32-kDa subunit of the red cell Rh blood group antigen, a new 28-kDa polypeptide was discovered (2). Detailed biochemical studies of this newly identified tetrameric membrane protein were made easy by its low solubility in N-lauroylsarcosine, which permitted simple purification (3). The abundance of the protein in rat renal proximal tubules and descending thin limbs (2) sparked the idea that the 28-kDa polypeptide may be the long sought water channel, and its unique N-terminal amino acid sequence permitted cloning from an erythroid cDNA library (4). Functional Analyses of AQP1The Xenopus oocyte expression system has been extremely useful for study of water transport. Oocytes injected with cRNA for the 28-kDa polypeptide exhibit remarkably high osmotic water permeability (P f ϳ200 ϫ 10 Ϫ4 cm s Ϫ1) and rapidly explode in hypotonic buffer (Fig. 1), whereas control oocytes exhibit minimal permeability (5). First referred to as "CHIP28," this protein is now designated aquaporin-1 (AQP1) 1 by the Human Genome Nomenclature Committee (see http://www.gene.ucl.ac.uk/nomenclature). Despite its large water permeability, AQP1 failed to confer a measurable increase in membrane currents (5). Consistent with these results, highly purified AQP1 protein reconstituted into proteoliposomes exhibits high unit water permeability (P f ϳ3 ϫ 10 9 water molecules subunit Ϫ1 s Ϫ1 ), whereas permeation by other small solutes or even protons was undetectable (6). The prevailing view is that AQP1 is a constitutively active, water-selective pore that permits osmotically driven movement of water. A report that forskolin induces a cation current in AQP1-expressing oocytes (7) was not reproduced by multiple other scientific groups. Permeation by CO 2 has recently been proposed, because rates of pH change are about 40% higher in oocytes expressing AQP1 (8). Permeation by O 2 , nitric oxide, and other gases is...

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“…18 Since the transport of glycerol by AQP3 is bidirectional, 59 proliferation could be related to the entry or exit of glycerol in cells; and unlike other authors, [60][61][62] we did not rule out the effect of Auphen on cell proliferation being caused by glycerol accumulation inside the cell due to blocking of the exit of glycerol. 18 AQP7 is the major pathway for glycerol efflux from adipocytes after lipolysis, 63,64 its absence resulting in increases in adipocyte cell volume and adipose tissue mass. 65,66 In the renal proximal tubule, AQP7 is a reabsorption pathway that may be important for preventing glycerol from being excreted into urine.…”

Section: Glycerolmentioning

confidence: 99%

Role of aquaporins in cell proliferation: What else beyond water permeability?

2016

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In addition to the extensive data demonstrating the importance of mammalian AQPs for the movement of water and some small solutes across the cell membrane, there is now a growing body of evidence indicating the involvement of these proteins in numerous cellular processes seemingly unrelated, at least some of them in a direct way, to their canonical function of water permeation. Here, we have presented a broad range of evidence demonstrating that these proteins have a role in cell proliferation by various different mechanisms, namely, by allowing fast cell volume regulation during cell division; by affecting progression of cell cycle and helping maintain the balance between proliferation and apoptosis, and by crosstalk with other cell membrane proteins or transcription factors that, in turn, modulate progression of the cell cycle or regulate biosynthesis pathways of cell structural components. In the end, however, after discussing all these data that strongly support a role for AQPs in the cell proliferation process, it remains impossible to conclude that all these other functions attributed to AQPs occur completely independently of their water permeability, and there is a need for new experiments designed specifically to address this interesting issue.

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Molecular Cloning and Expression of a Novel Human Aquaporin from Adipose Tissue with Glycerol Permeability

Cited by 165 publications

References 21 publications

Adaptation to fasting by glycerol transport through aquaporin 7 in adipose tissue

Adaptation to fasting by glycerol transport through aquaporin 7 in adipose tissue

The Aquaporins, Blueprints for Cellular Plumbing Systems

Role of aquaporins in cell proliferation: What else beyond water permeability?

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