Aquaporins in the plasma membrane of leaf callus protoplasts of Actinidia deliciosa var. deliciosa cv. Hayward

2000 ◽  
Vol 27 (1) ◽  
pp. 71
Author(s):  
Quan-Sheng Qiu ◽  
Ze-Zhou Wang ◽  
Nang Zhang ◽  
Qi-Gui Cai ◽  
Rong-Xi Jiang
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Imaging System ◽  
Inhibitory Effect ◽  
Actinidia Deliciosa ◽  
Transport Activity ◽  
Water Permeability Coefficient ◽  
Osmotic Water ◽  
A Cell ◽  
Protoplast Volume

The water transport activity of Actinidia deliciosa protoplasts was determined using a cell imaging system. Results showed that the protoplast volume increased swiftly when placed in a hypoton-ic medium, and also increased with an increase in medium osmotic gradients. The osmotic water permeability coefficient (Pf) values were 0.118 × 10–3, 0.121 × 10–3, and 0.133 × 10–3 cm s–1 when the osmotic gradients were 75, 100, and 125 mosmol, respectively. The water transport activity of protoplas-ts could be inhibited by HgCl2 and stimulated by amphotericin B. Moreover, ZnCl2 and ZnSO4 had a significant inhibitory effect on the water transport activity of the protoplasts. Our results indicate that the Actinidia deliciosa protoplasts had properties typical of aquaporins, suggesting that aquaporins were present at the plasma membrane.

scholarly journals Separation of Insulin Signaling into Distinct GLUT4 Translocation and Activation Steps

2004 ◽  
Vol 24 (17) ◽  
pp. 7567-7577 ◽  
Author(s):  
Makoto Funaki ◽  
Paramjeet Randhawa ◽  
Paul A. Janmey
Keyword(s):  
Plasma Membrane ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Time Lag ◽  
Inhibitory Effect ◽  
Glut4 Translocation ◽  
Glucose Levels ◽  
Increase Glucose Uptake ◽  
A Cell ◽  
Peptide Treatment

ABSTRACT GLUT4 (glucose transporter 4) plays a pivotal role in insulin-induced glucose uptake to maintain normal blood glucose levels. Here, we report that a cell-permeable phosphoinositide-binding peptide induced GLUT4 translocation to the plasma membrane without inhibiting IRAP (insulin-responsive aminopeptidase) endocytosis. However, unlike insulin treatment, the peptide treatment did not increase glucose uptake in 3T3-L1 adipocytes, indicating that GLUT4 translocation and activation are separate events. GLUT4 activation can occur at the plasma membrane, since insulin was able to increase glucose uptake with a shorter time lag when inactive GLUT4 was first translocated to the plasma membrane by pretreating the cells with this peptide. Inhibition of phosphatidylinositol (PI) 3-kinase activity failed to inhibit GLUT4 translocation by the peptide but did inhibit glucose uptake when insulin was added following peptide treatment. Insulin, but not the peptide, stimulated GLUT1 translocation. Surprisingly, the peptide pretreatment inhibited insulin-induced GLUT1 translocation, suggesting that the peptide treatment has both a stimulatory effect on GLUT4 translocation and an inhibitory effect on insulin-induced GLUT1 translocation. These results suggest that GLUT4 requires translocation to the plasma membrane, as well as activation at the plasma membrane, to initiate glucose uptake, and both of these steps normally require PI 3-kinase activation.

scholarly journals Aquaporin-1 Facilitates Transmesothelial Water Permeability: In Vitro and Ex Vivo Evidence and Possible Implications in Peritoneal Dialysis

2021 ◽  
Vol 22 (22) ◽  
pp. 12535
Author(s):  
Francesca Piccapane ◽  
Andrea Gerbino ◽  
Monica Carmosino ◽  
Serena Milano ◽  
Arduino Arduini ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Peritoneal Dialysis ◽  
Tight Junctions ◽  
Water Transport ◽  
Water Flux ◽  
Water Channel ◽  
Bathing Solution ◽  
Ussing Chambers ◽  
Aquaporin 1 ◽  
Osmotic Water

We previously showed that mesothelial cells in human peritoneum express the water channel aquaporin 1 (AQP1) at the plasma membrane, suggesting that, although in a non-physiological context, it may facilitate osmotic water exchange during peritoneal dialysis (PD). According to the three-pore model that predicts the transport of water during PD, the endothelium of peritoneal capillaries is the major limiting barrier to water transport across peritoneum, assuming the functional role of the mesothelium, as a semipermeable barrier, to be negligible. We hypothesized that an intact mesothelial layer is poorly permeable to water unless AQP1 is expressed at the plasma membrane. To demonstrate that, we characterized an immortalized cell line of human mesothelium (HMC) and measured the osmotically-driven transmesothelial water flux in the absence or in the presence of AQP1. The presence of tight junctions between HMC was investigated by immunofluorescence. Bioelectrical parameters of HMC monolayers were studied by Ussing Chambers and transepithelial water transport was investigated by an electrophysiological approach based on measurements of TEA+ dilution in the apical bathing solution, through TEA+-sensitive microelectrodes. HMCs express Zo-1 and occludin at the tight junctions and a transepithelial vectorial Na+ transport. Real-time transmesothelial water flux, in response to an increase of osmolarity in the apical solution, indicated that, in the presence of AQP1, the rate of TEA+ dilution was up to four-fold higher than in its absence. Of note, we confirmed our data in isolated mouse mesentery patches, where we measured an AQP1-dependent transmesothelial osmotic water transport. These results suggest that the mesothelium may represent an additional selective barrier regulating water transport in PD through functional expression of the water channel AQP1.

scholarly journals Secretin Promotes Osmotic Water Transport in Rat Cholangiocytes by Increasing Aquaporin-1 Water Channels in Plasma Membrane

1997 ◽  
Vol 272 (20) ◽  
pp. 12984-12988 ◽  
Author(s):  
Raul A. Marinelli ◽  
Linh Pham ◽  
Peter Agre ◽  
Nicholas F. LaRusso
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Water Channels ◽  
Aquaporin 1 ◽  
Osmotic Water

Mechanisms activating latent functions of PIP aquaporin water channels via the interaction between PIP1 and PIP2 proteins

2020 ◽  
Author(s):  
Mineo Shibasaka ◽  
Tomoaki Horie ◽  
Maki Katsuhara
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Molecular Mechanisms ◽  
Water Channel ◽  
Amino Acid Replacement ◽  
Middle Part ◽  
Single Amino Acid ◽  
Xenopus Laevis Oocytes ◽  
Transport Activity ◽  
Membrane Type

Abstract Plant plasma-membrane type PIP aquaporins are classified into two groups, PIP1s and PIP2s. In this study, we focused on HvPIP1; 2, a PIP1 in barley (Hordeum vulgare), to dissect the molecular mechanisms that evoke HvPIP1-mediated water transport. No HvPIP1; 2 protein was localized to the plasma membrane when expressed alone in Xenopus laevis oocytes. In contrast, a chimeric HvPIP1; 2 protein (HvPIP1; 2_24NC), in which the N- and C-terminal regions were replaced with the corresponding regions from HvPIP2; 4, was found to localize to the plasma membrane of oocytes. However, HvPIP1; 2_24NC showed no water transport activity in swelling assays. These results suggested that the terminal regions of PIP2 proteins direct PIP proteins to the plasma-membrane, but the re-localization of PIP1 proteins was not sufficient to PIP1s functionality as water channel in a membrane. A single amino acid replacement of threonine by methionine in HvPIP2; 4 (HvPIP2; 4T229M) abolished water transport activity. Co-expression of HvPIP1; 2_24NC either with HvPIP2; 4_12NC or HvPIP2; 4TM_12NC, in which the N- and C-terminal regions were replaced with the corresponding regions of HvPIP1; 2, increased the water transport activity in oocytes. These data provided evidence that the HvPIP1; 2 molecule has own water transport activity and an interaction with the middle part of the HvPIP2; 4 protein (except for the N- and C- termini) is required for HvPIP1; 2 functionality as water channel. This molecular mechanism could be applied to other PIP1s and PIP2s in addition to the known mechanism that the terminal regions of some PIP2s lead some PIP1s to the plasma membrane.

scholarly journals Water Transport Activity of the Plasma Membrane Aquaporin PM28A Is Regulated by Phosphorylation

1998 ◽  
Vol 10 (3) ◽  
pp. 451-459 ◽  
Author(s):  
Ingela Johansson ◽  
Maria Karlsson ◽  
Vipula K. Shukla ◽  
Maarten J. Chrispeels ◽  
Christer Larsson ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Transport Activity

scholarly journals Role of multiple phosphorylation sites in the COOH-terminal tail of aquaporin-2 for water transport: evidence against channel gating

2009 ◽  
Vol 296 (3) ◽  
pp. F649-F657 ◽  
Author(s):  
Hanne B. Moeller ◽  
Nanna MacAulay ◽  
Mark A. Knepper ◽  
Robert A. Fenton
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Water Permeability ◽  
Laser Scanning Microscopy ◽  
Apical Plasma Membrane ◽  
Phosphorylation Sites ◽  
Osmotic Water Permeability ◽  
Aquaporin 2 ◽  
Osmotic Water

Arginine vasopressin (AVP)-regulated phosphorylation of the water channel aquaporin-2 (AQP2) at serine 256 (S256) is essential for its accumulation in the apical plasma membrane of collecting duct principal cells. In this study, we examined the role of additional AVP-regulated phosphorylation sites in the COOH-terminal tail of AQP2 on protein function. When expressed in Xenopus laevis oocytes, prevention of AQP2 phosphorylation at S256A (S256A-AQP2) reduced osmotic water permeability threefold compared with wild-type (WT) AQP2-injected oocytes. In contrast, prevention of AQP2 single phosphorylation at S261 (S261A), S264 (S264A), and S269 (S269A), or all three sites in combination had no significant effect on water permeability. Similarly, oocytes expressing S264D-AQP2 and S269D-AQP2, mimicking AQP2 phosphorylated at these residues, had similar water permeabilities to WT-AQP2-expressing oocytes. The use of high-resolution confocal laser-scanning microscopy, as well as biochemical analysis demonstrated that all AQP2 mutants, with the exception of S256A-AQP2, had equal abundance in the oocyte plasma membrane. Correlation of osmotic water permeability relative to plasma membrane abundance demonstrated that lack of phosphorylation at S256, S261, S264, or S269 had no effect on AQP2 unit water transport. Similarly, no effect on AQP2 unit water transport was observed for the 264D and 269D forms, indicating that phosphorylation of the COOH-terminal tail of AQP2 is not involved in gating of the channel. The use of phosphospecific antibodies demonstrated that AQP2 S256 phosphorylation is not dependent on any of the other phosphorylation sites, whereas S264 and S269 phosphorylation depend on prior phosphorylation of S256. In contrast, AQP2 S261 phosphorylation is independent of the phosphorylation status of S256.

Water Transport Activity of the Plasma Membrane Aquaporin PM28A Is Regulated by Phosphorylation

1998 ◽  
Vol 10 (3) ◽  
pp. 451 ◽  
Author(s):  
Ingela Johansson ◽  
Maria Karlsson ◽  
Vipula K. Shukla ◽  
Maarten J. Chrispeels ◽  
Christer Larsson ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Transport Activity

scholarly journals Importance of the mercury-sensitive cysteine on function and routing of AQP1 and AQP2 in oocytes

1997 ◽  
Vol 273 (3) ◽  
pp. F451-F456 ◽  
Author(s):  
S. M. Mulders ◽  
J. P. Rijss ◽  
A. Hartog ◽  
R. J. Bindels ◽  
C. H. van Os ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Water Transport ◽  
Water Permeability ◽  
Nephrogenic Diabetes Insipidus ◽  
Osmotic Water Permeability ◽  
Wild Type ◽  
Mutant Proteins ◽  
Osmotic Water ◽  
Structural Differences

To discriminate between water transport of of aquaporin-2 (AQP2) mutants in nephrogenic diabetes insipidus and that of an AQP2 molecule used to drag them to the oolemma, we investigated the mercury sensitivity of wild-type and AQP2 C181S proteins in oocytes. Incubation with HgCl2 inhibited the osmotic water permeability (Pf) of human (h) AQP2 by 40%, whereas inhibition of hAQP1 was 75%. Oocytes expressing hAQP1 C189S revealed a Pf comparable to wild-type hAQP1, but mercury sensitivity was lost. In contrast, no increase in Pf was obtained when hAQP2 C181S was expressed. Also, expression of rat AQP2 C181A and C181S mutants did not increase the Pf, which contrasts with published observations. Immunocytochemistry and immunoblotting revealed that only AQP1, AQP1 C189S, and AQP2 were targeted to the plasma membrane and that AQP2 mutant proteins are retarded in the endoplasmic reticulum. In conclusion, water transport through AQP2 is less sensitive to mercury inhibition than through AQP1. Furthermore, substitution of the mercury-sensitive cysteine for a serine results in an impaired routing of human and rat AQP2. Similar mutations have no effect on AQP1 function, which is indicative of structural differences between AQP1 and AQP2.

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