Cloning and Functional Expression of a New Water Channel Abundantly Expressed in the Testis Permeable to Water, Glycerol, and Urea

Ishibashi, Keiichiro; Kuwahara, Michio; Gu, Yong; Kageyama, Yukio; Tohsaka, Akira; Suzuki, Fumie; Marumo, Fumiaki; Sasaki, Sei

doi:10.1074/jbc.272.33.20782

Cited by 358 publications

(263 citation statements)

References 19 publications

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“…AQP7 is an aquaglyceroporin that is abundantly expressed in kidney, testis, and adipocytes (6,9). Moreover, AQP7 is also known to allow rapid urea and arsenite transport (6,12). In the kidney, AQP7 is expressed on the apical membrane of the proximal straight tubules (S3 segment) (6), where AQP1 is also present (19).…”

mentioning

confidence: 99%

“…Moreover, AQP7 is also known to allow rapid urea and arsenite transport (6,12). In the kidney, AQP7 is expressed on the apical membrane of the proximal straight tubules (S3 segment) (6), where AQP1 is also present (19). Studies of AQP1 knockout mice have shown that AQP1 plays a major role in proximal tubular water transport (15,22).…”

mentioning

confidence: 99%

“…Some AQPs are classified as part of the aquaglyceroporin family, the members of which facilitate the transport of glycerol as well as water (7). AQP7 is an aquaglyceroporin that is abundantly expressed in kidney, testis, and adipocytes (6,9). Moreover, AQP7 is also known to allow rapid urea and arsenite transport (6,12).…”

mentioning

confidence: 99%

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Defective water and glycerol transport in the proximal tubules of AQP7 knockout mice

Sohara¹,

Rai²,

Miyazaki³

et al. 2005

American Journal of Physiology-Renal Physiology

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water channel is known as a member of the aquaglyceroporins, which facilitate the transport of glycerol as well as water. Although AQP7 is abundantly expressed on the apical membrane of the proximal straight tubules in the kidney, the physiological role of AQP7 is still unknown. To investigate this, we generated AQP7 knockout mice. The water permeability of the proximal tubule brush-border membrane measured by the stopped-flow method was slightly but significantly reduced in the AQP7 knockout mice compared with that of wild-type mice (AQP7, 18.0 Ϯ 0.4 ϫ 10 Ϫ3 cm/s vs. wild-type, 20.0 Ϯ 0.3 ϫ 10 Ϫ3 cm/s). Although AQP7 solo-knockout mice did not exhibit a urinary concentrating defect, AQP1/AQP7 double-knockout mice had a reduction in urinary concentrating ability compared with AQP1 soloknockout mice, suggesting that the amount of water reabsorbed through AQP7 in the proximal straight tubules is physiologically substantial. On the other hand, AQP7 knockout mice showed marked glyceroluria (AQP7, 1.7 Ϯ 0.34 mg/ml vs. wild-type, 0.005 Ϯ 0.002 mg/ml). This identified a novel glycerol reabsorption pathway in the proximal straight tubules. In two mouse models of proximal straight tubule injury, the cisplatin-induced acute renal failure (ARF) model and the ischemic ARF model, an increase in urine glycerol was observed (pretreatment, 0.007 Ϯ 0.005 mg/ml; cisplatin, 0.063 Ϯ 0.043 mg/ml; ischemia, 0.076 Ϯ 0.02 mg/ml), suggesting that urine glycerol could be used as a new biomarker for detecting proximal straight tubule injury.

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Defective water and glycerol transport in the proximal tubules of AQP7 knockout mice

Sohara¹,

Rai²,

Miyazaki³

et al. 2005

American Journal of Physiology-Renal Physiology

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“…As it was cloned and identified first in the rat testis [59], reports on AQP7 on germ cells and spermatozoa have been most consistent among AQPs ( Table 1). The diffuse staining of the cytoplasm, in addition to the plasma membrane (also for AQP8), may represent the degraded protein in view of the dynamic formation and differentiation of spermatids ( Figure 1A and B).…”

Section: Aqp7mentioning

confidence: 94%

Aquaporins in spermatozoa and testicular germ cells: identification and potential role

Yeung¹

2010

Asian J Androl

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Mammalian spermatozoa have relatively high water permeability and swell readily, as in the hypo-osmotic swelling test used in the andrology clinic. Physiologically, spermatozoa experience changes in the osmolality of the surrounding fluids in both the male and the female tracts on their journey from the testis to the ovum. Sperm volume regulation in response to such osmotic challenges is important to maintain a stable cell size for the normal shape and function of the sperm tail. Alongside ion channels for the fluxes of osmolytes, water channels would be crucial for sperm volume regulation. In contrast to the deep knowledge and numerous studies on somatic cell aquaporins (AQPs), the understanding of sperm AQPs is limited. Among the 13 AQPs, convincing evidence for their presence in spermatozoa has been confined to AQP7, AQP8 and AQP11. Overall, current findings indicate a major role of AQP8 in water influx and efflux for sperm volume regulation, which is required for natural fertilization. The preliminary data suggestive of a role for AQP7 in sperm glycerol metabolism needs further substantiation. The association of AQP11 with the residual cytoplasm of elongated spermatids and the distal tail of spermatozoa supports the hypothesis of more than just a role in conferring water permeability and also in the turnover and recycling of surplus cellular components made redundant during spermiogenesis and spermiation. This would be crucial for the maintenance of a germinal epithelium functioning efficiently in the production of spermatozoa.

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“…Recently, it was proposed that aquaporins might be active players in sperm volume-regulatory water fl ux [11] . Indeed, two aquaporins (AQP7 and 8) were fi rst cloned from rat testes and identifi ed by staining in murine sperm tails [12][13][14] . Aquaporin-11 (AQP11) has also been found in the end piece of rat sperm [15] (although some controversies exist due to variable antibody specifi city; for a more detailed description, see the comprehensive review [14] ).…”

Section: Efficient Sperm Volume Regulation Is a Prerequisite For Normmentioning

confidence: 99%

Aquaporins in sperm osmoadaptation: an emerging role for volume regulation

Chen

Duan

2011

Acta Pharmacol Sin

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Upon ejaculation, mammalian sperm experience a natural osmotic decrease during male to female reproductive tract transition. This hypo-osmotic exposure not only activates sperm motility, but also poses potential harm to sperm structure and function by inducing unwanted cell swelling. In this physiological context, regulatory volume decrease (RVD) is the major mechanism that protects cells from detrimental swelling, and is essential to sperm survival and normal function. Aquaporins are selective water channels that enable rapid water transport across cell membranes. Aquaporins have been implicated in sperm osmoregulation. Recent discoveries show that Aquaporin-3 (AQP3), a water channel protein, is localized in sperm tail membranes and that AQP3 mutant sperm show defects in volume regulation and excessive cell swelling upon physiological hypotonic stress in the female reproductive tract, thereby highlighting the importance of AQP3 in the postcopulatory sperm RVD process. In this paper, we discuss current knowledge, remaining questions and hypotheses about the function and mechanismic basis of aquaporins for volume regulation in sperm and other cell types. Efficient sperm volume regulation is a prerequisite for normal sperm functionIn most mammalian species studied, the journey of sperm from the male to the female reproductive tract experience a natural osmotic decrease [1] , an evolutionary vestige from freshwater fi sh species [2] . Before ejaculation, the mammalian sperm are quiescent in the relatively hypertonic male reproductive tract with no or very low motility. Upon copulation, the sperm enter into the relatively hypotonic female reproductive tract and quickly show motility activation [3,4] , indicating that osmotic changes are beneficial for initial sperm motility activation. However, postcopulatory hypotonic stress also has a negative effects as it induces osmotic cell swelling, which if uncontrolled, can be detrimental to sperm function and survival [5] . Mammalian sperm have evolved to effectively reduce the negative impact of hypotonic cell swelling by means of regulatory volume decrease (RVD), which was proposed to involve efficient volume regulation driven by active solute transport and rapid transmembrane water movement [6] .Functional importance of aquaporins in sperm volume regulation: emerging evidence from AQP3 knockout miceIn the early 1970s, it was demonstrated that the water permeability coefficient of bull spermatozoa was quite high, about four times greater than that of bovine erythrocytes and between ten and thirty times greater than that of artificial bimolecular lipid membranes [7] . According to these observations, the author made an insightful conclusion that the chief route for the passage of water through the sperm membrane must be via "pores" [7] . Similar high water permeability coefficients have been discovered in other mammalian species, including humans [8,9] .In the past two decades, the understanding of the movement of water through cell membranes has been greatly advanced by ...

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Cloning and Functional Expression of a New Water Channel Abundantly Expressed in the Testis Permeable to Water, Glycerol, and Urea

Cited by 358 publications

References 19 publications

Defective water and glycerol transport in the proximal tubules of AQP7 knockout mice

Defective water and glycerol transport in the proximal tubules of AQP7 knockout mice

Aquaporins in spermatozoa and testicular germ cells: identification and potential role

Aquaporins in sperm osmoadaptation: an emerging role for volume regulation

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