scholarly journals Vasotocin/V2-Type Receptor/Aquaporin Axis Exists in African Lungfish Kidney but Is Functional Only in Terrestrial Condition

Endocrinology ◽  
2010 ◽  
Vol 151 (3) ◽  
pp. 1089-1096 ◽  
Author(s):  
Norifumi Konno ◽  
Susumu Hyodo ◽  
Yoko Yamaguchi ◽  
Kouhei Matsuda ◽  
Minoru Uchiyama
Keyword(s):  
Xenopus Oocytes ◽  
Distal Tubule ◽  
Apical Plasma Membrane ◽  
Mrna Levels ◽  
Water Reabsorption ◽  
Terrestrial Environment ◽  
Terrestrial Condition ◽  
African Lungfish ◽  
Type Receptor ◽  
Antidiuretic Action

The vasopressin/vasotocin (VT)-V2-type receptor (V2R)-aquaporin (AQP)-2 axis plays a pivotal role in renal water reabsorption in tetrapods. It is widely thought that this axis evolved with the emergence of the tetrapods, reflecting a requirement of water retention in terrestrial environment. Here we report that lungfish, the closest living relatives of tetrapods, already possess a system similar to the VT-V2R-AQP2 axis in the kidney, but the system is functional only in the terrestrial estivating condition. We cloned a novel AQP paralogous to AQP0. The water permeability of Xenopus oocytes was increased by injection with the AQP cRNA and was further facilitated by preincubation with cAMP. In the kidney of estivating lungfish, the AQP protein was localized on the apical plasma membrane of the late distal tubule and was colocalized with basolateral V2R. By contrast, we found only little expression of the AQP mRNA and protein in the kidney of lungfish in aquatic condition. The expression levels of mRNA and protein were dramatically increased during estivation and decreased again by reacclimation of estivating lungfish to water. The AQP mRNA levels positively correlated with the VT mRNA levels in the hypothalamus, suggesting that the AQP exerts tubular antidiuretic action under control of VT. Because the tetrapod AQP2/AQP5 lineage is considered to be evolved from duplication of an AQP0 gene, the paralogous AQP0 in the lungfish probably represents ancestral molecule for tetrapod AQP2.

Comparison of intestinal folate carrier clone expressed in IEC-6 cells and in Xenopusoocytes

1998 ◽  
Vol 274 (1) ◽  
pp. C289-C294 ◽  
Author(s):  
Chandira K. Kumar ◽  
Toai T. Nguyen ◽  
Francis B. Gonzales ◽  
Hamid M. Said
Keyword(s):  
Folic Acid ◽  
Epithelial Cells ◽  
Cdna Clone ◽  
Xenopus Oocytes ◽  
Intestinal Epithelial Cells ◽  
Maximal Velocity ◽  
Mrna Levels ◽  
Acidic Ph ◽  
Intestinal Epithelial ◽  
Folate Transport

We recently identified a cDNA clone from mouse small intestine, which appears to be involved in folate transport when expressed in Xenopus oocytes. The open reading frame of this clone is identical to that of the reduced folate carrier (RFC) (K. H. Dixon, B. C. Lanpher, J. Chiu, K. Kelley, and K. H. Cowan. J. Biol. Chem. 269: 17–20, 1994). The characteristics of this cDNA clone [previously referred to as intestinal folate carrier 1 (IFC-1)] expressed in Xenopus oocytes, however, were found to be different from the characteristics of folate transport in native small intestinal epithelial cells. To further study these differences, we determined the characteristics of RFC when expressed in an intestinal epithelial cell line, IEC-6, and compared the findings to its characteristics when expressed in Xenopus oocytes. RFC was stably transfected into IEC-6 cells by electroporation; its cRNA was microinjected into Xenopus oocytes. Northern blot analysis of poly(A)+RNA from IEC-6 cells stably transfected with RFC cDNA (IEC-6/RFC) showed a twofold increase in RFC mRNA levels over controls. Similarly, uptake of folic acid and 5-methyltetrahydrofolate (5-MTHF) by IEC-6/RFC was found to be fourfold higher than uptake in control sublines. This increase in folic acid and 5-MTHF uptake was inhibited by treating IEC-6/RFC cells with cholesterol-modified antisense DNA oligonucleotides. The increase in uptake was found to be mainly mediated through an increase in the maximal velocity ( V max) of the uptake process [the apparent Michaelis-Menten constant ( K m) also changed (range was 0.31 to 1.56 μM), but no specific trend was seen]. In both IEC-6/RFC and control sublines, the uptake of both folic acid and 5-MTHF displayed 1) pH dependency, with a higher uptake at acidic pH 5.5 compared with pH 7.5, and 2) inhibition to the same extent by both reduced and oxidized folate derivatives. These characteristics are very similar to those seen in native intestinal epithelial cells. In contrast, RFC expressed in Xenopus oocytes showed 1) higher uptake at neutral and alkaline pH 7.5 compared with acidic pH 5.5 and 2) higher sensitivity to reduced compared with oxidized folate derivatives. Results of these studies demonstrate that the characteristics of RFC vary depending on the cell system in which it is expressed. Furthermore, the results may suggest the involvement of cell- or tissue-specific posttranslational modification(s) and/or the existence of an auxiliary protein that may account for the differences in the characteristics of the intestinal RFC when expressed in Xenopus oocytes compared with when expressed in intestinal epithelial cells.

scholarly journals Rab7 involves Vps35 to mediate AQP2 sorting and apical trafficking in collecting duct cells

2020 ◽  
Vol 318 (4) ◽  
pp. F956-F970 ◽  
Author(s):  
Wei-Ling Wang ◽  
Shih-Han Su ◽  
Kit Yee Wong ◽  
Chan-Wei Yang ◽  
Chin-Fu Liu ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Apical Membrane ◽  
Collecting Duct ◽  
Water Channel ◽  
Small Gtpase ◽  
Apical Plasma Membrane ◽  
Water Reabsorption ◽  
Recycling Endosomes ◽  
Early Endosomes ◽  
Vacuolar Protein

Aquaporin-2 (AQP2) is a vasopressin-regulated water channel protein responsible for osmotic water reabsorption by kidney collecting ducts. In response to vasopressin, AQP2 traffics from intracellular vesicles to the apical plasma membrane of collecting duct principal cells, where it increases water permeability and, hence, water reabsorption. Despite continuing efforts, gaps remain in our knowledge of vasopressin-regulated AQP2 trafficking. Here, we studied the functions of two retromer complex proteins, small GTPase Rab7 and vacuolar protein sorting 35 (Vps35), in vasopressin-induced AQP2 trafficking in a collecting duct cell model (mpkCCD cells). We showed that upon vasopressin removal, apical AQP2 returned to Rab5-positive early endosomes before joining Rab11-positive recycling endosomes. In response to vasopressin, Rab11-associated AQP2 trafficked to the apical plasma membrane before Rab5-associated AQP2 did so. Rab7 knockdown resulted in AQP2 accumulation in early endosomes and impaired vasopressin-induced apical AQP2 trafficking. In response to vasopressin, Rab7 transiently colocalized with Rab5, indicative of a role of Rab7 in AQP2 sorting in early endosomes before trafficking to the apical membrane. Rab7-mediated apical AQP2 trafficking in response to vasopressin required GTPase activity. When Vps35 was knocked down, AQP2 accumulated in recycling endosomes under vehicle conditions and did not traffic to the apical plasma membrane in response to vasopressin. We conclude that Rab7 and Vps35 participate in AQP2 sorting in early endosomes under vehicle conditions and apical membrane trafficking in response to vasopressin.

Immunocytochemical studies of the Na-K-Cl cotransporter of shark kidney

1996 ◽  
Vol 270 (6) ◽  
pp. F927-F936 ◽  
Author(s):  
D. Biemesderfer ◽  
J. A. Payne ◽  
C. Y. Lytle ◽  
B. Forbush
Keyword(s):  
Plasma Membrane ◽  
Immunoelectron Microscopy ◽  
Basolateral Membrane ◽  
Distal Tubule ◽  
Rectal Gland ◽  
Apical Plasma Membrane ◽  
Secretory Cells ◽  
Weak Staining ◽  
Basolateral Plasma Membrane ◽  
Kidney Functions

The Na-K-Cl cotransporter (NKCC or BSC) has been described in numerous secretory and reabsorptive epithelia and is an important part of the mechanism of NaCl reabsorption in both the mammalian and elasmobranch kidneys. We have recently developed a panel of four monoclonal antibodies (MAbs) raised to the 195-kDa Na-K-Cl cotransport protein of the shark rectal gland (sNKCC1), which is expressed along the basolateral plasma membrane of secretory cells in this tissue (29). Here, we report immunologic studies of the Na-K-Cl cotransporter in the kidney of the dogfish shark Squalus acanthias. Western blot analysis of shark renal microsomes using MAbs J3, J7, and J25 identified proteins of approximately 195 and 150 kDa, whereas MAb J4 was not reactive. To define the cellular and subcellular distribution of the cotransport protein, immunofluorescence and immunoelectron microscopy studies were performed on fixed kidneys. Immunofluorescence microscopy on semithin (0.5-micron) cryosections demonstrated that MAbs J3, J7, and J25 intensely stained the apical plasma membrane of all distal tubule segments. Weak staining was also seen along the basolateral membrane of most distal nephrons. Immunoelectron microscopy confirmed this observation and showed that some of these segments were morphologically similar to diluting segments from other species. MAbs also reacted with the brush border and, to a lesser extent, the basolateral membrane of proximal tubules. This study supports the hypothesis that the lateral bundle zone of the elasmobranch kidney functions as a countercurrent exchanger and is consistent with the presence of multiple isoforms of the Na-K-Cl cotransporter in the shark kidney.

Advances in aquaporin-2 trafficking mechanisms and their implications for treatment of water balance disorders

2020 ◽  
Vol 319 (1) ◽  
pp. C1-C10 ◽  
Author(s):  
Robert A. Fenton ◽  
Sathish K. Murali ◽  
Hanne B. Moeller
Keyword(s):  
Protein Interactions ◽  
Collecting Duct ◽  
Water Channel ◽  
Plasma Osmolality ◽  
Carboxyl Terminus ◽  
Apical Plasma Membrane ◽  
Tail Domain ◽  
Water Reabsorption ◽  
Aquaporin 2

In mammals, conservation of body water is critical for survival and is dependent on the kidneys’ ability to minimize water loss in the urine during periods of water deprivation. The collecting duct water channel aquaporin-2 (AQP2) plays an essential role in this homeostatic response by facilitating water reabsorption along osmotic gradients. The ability to increase the levels of AQP2 in the apical plasma membrane following an increase in plasma osmolality is a rate-limiting step in water reabsorption, a process that is tightly regulated by the antidiuretic hormone arginine vasopressin (AVP). In this review, the focus is on the role of the carboxyl-terminus of AQP2 as a key regulatory point for AQP2 trafficking. We provide an overview of AQP2 structure, disease-causing mutations in the AQP2 carboxyl-terminus, the role of posttranslational modifications such as phosphorylation and ubiquitylation in the tail domain, and their implications for balanced trafficking of AQP2. Finally, we discuss how various modifications of the AQP2 tail facilitate selective protein-protein interactions that modulate the AQP2 trafficking mechanism.

Regulation of the immunoexpression of aquaporin 9 by ovarian hormones in the rat oviductal epithelium

2005 ◽  
Vol 288 (5) ◽  
pp. C1048-C1057 ◽  
Author(s):  
María C. Brañes ◽  
Bernardo Morales ◽  
Mariana Ríos ◽  
Manuel J. Villalón
Keyword(s):  
Steroid Hormones ◽  
Estrous Cycle ◽  
Hormonal Regulation ◽  
Water Movement ◽  
Water Channels ◽  
Hormonal Control ◽  
Apical Plasma Membrane ◽  
Functional Assay ◽  
Mrna Levels ◽  
Oviductal Epithelium

The volume of oviductal fluid fluctuates during the estrous cycle, suggesting that water availability is under hormonal control. It has been postulated that sex-steroid hormones may regulate aquaporin (AQP) channels involved in water movement across cell membranes. Using a functional assay (oocytes of Xenopus laevis), we demonstrated that the rat oviductal epithelium contains mRNAs coding for water channels, and we identified by RT-PCR the mRNAs for AQP5, -8, and -9, but not for AQP2 and -3. The immunoreactivity for AQP5, -8, and -9 was localized only in epithelial cells of the oviduct. The distribution of AQP5 and -8 was mainly cytoplasmic, whereas we confirmed, by confocal microscopy, that AQP9 localized to the apical plasma membrane. Staining of AQP5, -8, and -9 was lost after ovariectomy, and only AQP9 immunoreactivity was restored after estradiol and/or progesterone treatments. The recovery of AQP9 reactivity after ovariectomy correlated with increased mRNA and protein levels after treatment with estradiol alone or progesterone administration after estradiol priming. Interestingly, progesterone administration after progesterone priming also induced AQP9 expression but without a change in mRNA levels. Levels of AQP9 varied along the estrous cycle with their highest levels during proestrus and estrus. These results indicate that steroid hormones regulate AQP9 expression at the mRNA and protein level and that other ovarian signals are involved in the expression of AQP5 and -8. Thus hormonal regulation of the type and quantity of water channels in this epithelium might control water transport in the oviductal lumen.

Structural-functional relationships along the distal nephron

1986 ◽  
Vol 250 (1) ◽  
pp. F1-F15 ◽  
Author(s):  
K. M. Madsen ◽  
C. C. Tisher
Keyword(s):  
Atpase Activity ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Distal Tubule ◽  
Structural Heterogeneity ◽  
Apical Plasma Membrane ◽  
Thick Ascending Limb ◽  
Intercalated Cells ◽  
Principal Cells ◽  
Functional Relationships

The distal tubule, which includes the thick ascending limb (TAL), the macula densa, and the distal convoluted tubule (DCT), and the collecting duct are structurally heterogeneous, thus reflecting the functional heterogeneity that is also present. As the TAL ascends from medulla to cortex, the surface area of the apical plasma membrane increases while that of the basolateral membrane decreases. The structure of the DCT resembles that of the medullary TAL. An excellent correlation exists between structure, Na-K-ATPase activity, and NaCl reabsorptive capacity in the distal tubule. The collecting duct is subdivided into the initial collecting tubule (ICT), and cortical (CCD), outer medullary (OMCD), and inner medullary (IMCD) collecting ducts. Between the distal tubule and the collecting duct is a transition region termed the connecting segment or connecting tubule (CNT). Considerable structural heterogeneity exists along the collecting duct within the two major cell populations, the intercalated cells and the principal cells. In the CNT, the ICT, and the CCD, potassium loading and mineralocorticoids stimulate Na-K-ATPase activity and cause proliferation of the basolateral membrane of CNT cells and principal cells, thus identifying the cells responsible for mineralocorticoid-stimulated potassium secretion in these regions. Finally, at least two morphologically distinct populations of intercalated cells exist, types A and B. In the rat, type A predominates in the CNT and the OMCD and is believed to be responsible for H+ secretion, at least in the OMCD. Type B predominates in the CCD, where it may be involved in bicarbonate secretion.

Role of deep nephrons and the terminal collecting duct in a mannitol-induced diuresis

1981 ◽  
Vol 240 (5) ◽  
pp. F411-F422 ◽  
Author(s):  
J. Buerkert ◽  
D. Martin ◽  
J. Prasad ◽  
D. Trigg
Keyword(s):  
Plasma Flow ◽  
Collecting Duct ◽  
Renal Plasma Flow ◽  
Distal Tubule ◽  
Sodium Reabsorption ◽  
Water Reabsorption ◽  
Single Nephron ◽  
Papillary Collecting Duct ◽  
Reduced Water

Recollection micropuncture in Munich-Wistar rats was used to study the effects of intravenous hypertonic mannitol infusions on fluid reabsorption by surface nephrons, prior to the bend of Henle's loop of deep nephrons, and along the papillary collecting duct. During mannitol diuresis, single nephron glomerular filtration rate rose significantly in surface nephrons but fell in deep nephrons. Although mannitol increased the delivery of sodium and water to the end of the proximal tubule and to the first portion of the distal tubule of surface nephrons, water and sodium were reabsorbed between these two sites. In deep nephrons, water reabsorption prior to the bend of the loop of Henle was significantly decreased. Absolute sodium delivery to this site was reduced despite a marked decrease in fractional sodium reabsorption prior to the bend. Papillary osmolality was decreased. Renal plasma flow and inner medullary plasma flow (IMPF) increased proportionally. The reduced water extraction prior to the bend of deep nephrons and the decrease in papillary osmolality could have been partly due to a concomitant increase in IMPF and a decrease in sodium delivery to the medulla. The reabsorption of delivered sodium and water by the papillary collecting duct was reduced to a greater extent than could be expected from the increase in sodium delivery.

Surviving rat distal tubule bicarbonate reabsorption: effects of chronic AT1 blockade

2000 ◽  
Vol 278 (3) ◽  
pp. F476-F483 ◽  
Author(s):  
David Z. Levine ◽  
Michelle Iacovitti ◽  
Brian Luck ◽  
Maxwell T. Hincke ◽  
Kevin D. Burns ◽  
...  
Keyword(s):  
Distal Tubule ◽  
Apical Plasma Membrane ◽  
Intercalated Cells ◽  
Protein Levels ◽  
Bicarbonate Reabsorption ◽  
Concanamycin A ◽  
Dimethyl Amiloride ◽  
In Vivo Effects

To determine the in vivo effects of chronic ANG II type 1 (AT1)-receptor blockade by losartan (Los) on enhanced unidirectional bicarbonate reabsorption ( J HCO3 ) of surviving distal tubules, nephrectomized rats drank either water or a solution of Los, 7 days before microperfusion. J HCO3 was suppressed by 50% after Los without further reduction by 5 nM concanamycin A (Conc), suggesting that Los suppresses all Conc-sensitive H+-ATPase pumping. Indeed, ultrastructural analysis of A-type intercalated cells revealed a 50% reduction of H+-ATPase immunogold labeling of the apical plasma membrane, whereas Western blotting showed that H+-ATPase protein levels were also reduced by one-half by Los treatment. To identify other transporters sustaining J HCO3 , we perfused three inhibitors simultaneously [5-( N, N-dimethyl) amiloride hydrochloride, Conc, Schering 28080] with or without prior Los treatment: J HCO3 was unchanged despite marked reduction of water reabsorption. We conclude enhanced distal tubule J HCO3 of surviving nephrons is largely mediated by AT1 receptor-dependent synthesis and insertion of apical H+-ATPase pumps in A-type intercalated cells.

Gene expression and localization of two types of AQP5 inXenopus tropicalisunder hydration and dehydration

2014 ◽  
Vol 307 (1) ◽  
pp. R44-R56 ◽  
Author(s):  
Yuki Shibata ◽  
Takahiro Sano ◽  
Nobuhito Tsuchiya ◽  
Reiko Okada ◽  
Hiroshi Mochida ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Urinary Bladder ◽  
Apical Plasma Membrane ◽  
Secretory Cells ◽  
Granular Cells ◽  
Aquaporin 5 ◽  
Water Reabsorption ◽  
Molecular Phylogenetic ◽  
Water Secretion ◽  
Hydration And Dehydration

Two types of aquaporin 5 (AQP5) genes ( aqp-xt5a and aqp-xt5b) were identified in the genome of Xenopus tropicalis by synteny comparison and molecular phylogenetic analysis. When the frogs were in water, AQP-xt5a mRNA was expressed in the skin and urinary bladder. The expression of AQP-xt5a mRNA was significantly increased in dehydrated frogs. AQP-xt5b mRNA was also detected in the skin and increased in response to dehydration. Additionally, AQP-xt5b mRNA began to be slightly expressed in the lung and stomach after dehydration. For the pelvic skin of hydrated frogs, immunofluorescence staining localized AQP-xt5a and AQP-xt5b to the cytoplasm of secretory cells of the granular glands and the apical plasma membrane of secretory cells of the small granular glands, respectively. After dehydration, the locations of both AQPs in their respective glands did not change, but AQP-xt5a was visualized in the cytoplasm of secretory cells of the small granular glands. For the urinary bladder, AQP-xt5a was observed in the apical plasma membrane and cytoplasm of a number of granular cells under normal hydration. After dehydration, AQP-xt5a was found in the apical membrane and cytoplasm of most granular cells. Injection of vasotocin into hydrated frogs did not induce these changes in the localization of AQP-xt5a in the small granular glands and urinary bladder, however. The results suggest that AQP-xt5a might be involved in water reabsorption from the urinary bladder during dehydration, whereas AQP-xt5b might play a role in water secretion from the small granular gland.

scholarly journals Compensatory increase in AQP2, p-AQP2, and AQP3 expression in rats with diabetes mellitus

2001 ◽  
Vol 280 (4) ◽  
pp. F715-F726 ◽  
Author(s):  
Lene N. Nejsum ◽  
Tae-Hwan Kwon ◽  
David Marples ◽  
Allan Flyvbjerg ◽  
Mark A. Knepper ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Plasma Membrane ◽  
Sodium Excretion ◽  
Collecting Duct ◽  
Distal Tubule ◽  
Urinary Sodium Excretion ◽  
Apical Plasma Membrane ◽  
Compensatory Increase ◽  
Intracellular Vesicles

Diabetes mellitus (DM) is associated with osmotic diuresis and natriuresis. At day 15, rats with DM induced by streptozotocin ( n = 13) had severe hyperglycemia (27.1 ± 0.4 vs. 4.7 ± 0.1 mM in controls) and had a fivefold increase in water intake (123 ± 5 vs. 25 ± 2 ml/day) and urine output. Semiquantitative immunoblotting revealed a significant increase in inner medullary AQP2 (201 ± 12% of control rats, P < 0.05) and phosphorylated (Ser256) AQP2 (p-AQP2) abundance (299 ± 32%) in DM rats. Also, the abundance of inner medullary AQP3 was markedly increased to 171 ± 19% of control levels (100 ± 4%, n = 7, P < 0.05). In contrast, the abundance of whole kidney AQP1 (90 ± 3%) and inner medullary AQP4 (121 ± 16%) was unchanged in rats with DM. Immunoelectron microscopy further revealed an increased labeling of AQP2 in the apical plasma membrane of collecting duct principal cells (with less labeling in the intracellular vesicles) of DM rats, indicating enhanced trafficking of AQP2 to the apical plasma membrane. There was a marked increase in urinary sodium excretion in DM. Only Na+/H+ exchanger NHE3 was downregulated (67 ± 10 vs. 100 ± 11%) whereas there were no significant changes in abundance of type 2 Na-phosphate cotransporter (128 ± 6 vs. 100 ± 10%); the Na-K-2Cl cotransporter (125 ± 19 vs. 100 ± 10%); the thiazide-sensitive Na-Cl cotransporter (121 ± 9 vs. 100 ± 10%); the α1-subunit of the Na-K-ATPase (106 ± 7 vs. 100 ± 5%); and the proximal tubule Na-HCO3 cotransporter (98 ± 16 vs. 100 ± 7%). In conclusion, DM rats had an increased AQP2, p-AQP2, and AQP3 abundance as well as high AQP2 labeling of the apical plasma membrane, which is likely to represent a vasopressin-mediated compensatory increase in response to the severe polyuria. In contrast, there were no major changes in the abundance of AQP1, AQP4, and several major proximal and distal tubule Na+ transporters except NHE3 downregulation, which may participate in the increased sodium excretion.

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