scholarly journals β-Klotho as a Negative Regulator of the Peptide Transporters PEPT1 and PEPT2

2016 ◽  
Vol 40 (5) ◽  
pp. 874-882 ◽  
Author(s):  
Abeer Abousaab ◽  
Jamshed Warsi ◽  
Madhuri S. Salker ◽  
Florian Lang
Keyword(s):  
Transmembrane Protein ◽  
Ussing Chamber ◽  
Negative Regulator ◽  
Peptide Transport ◽  
Xenopus Laevis Oocytes ◽  
Intestinal Epithelia ◽  
Peptide Transporters ◽  
Klotho Protein ◽  
Glycine Transport ◽  
The Brain

Background/Aims: β-Klotho, a transmembrane protein expressed in several tissues including the brain and the kidney, is critically important for inhibition of 1,25(OH)2D3 formation by FGF23. The extracellular domain of Klotho protein could be cleaved off, thus being released into blood or cerebrospinal fluid. Soluble klotho is a β-glucuronidase participating in the regulation of several ion channels and carriers. The present study explored the effect of β-Klotho protein on the peptide transporters PEPT1 and PEPT2. Methods: cRNA encoding PEPT1 or PEPT2 was injected into Xenopus laevis oocytes and glycine-glycine (2 mM)-induced inward current (IGly) taken as measure of glycine-glycine transport. Measurements were made without or with prior 24 h treatment with soluble β-Klotho protein (30 ng/ml) in the absence and presence of β-glucuronidase inhibitor D-saccharic acid 1,4-lactone monohydrate (DSAL,10 µM). Ussing chamber experiments were employed to determine electrogenic peptide transport across intestinal epithelia of klotho deficient (kl-/-) and corresponding wild type (kl+/+) mice. Results: IGly was observed in PEPT1 and in PEPT2 expressing oocytes but not in water injected oocytes. In both, PEPT1 and PEPT2 expressing oocytes IGly was significantly decreased by treatment with soluble β-Klotho protein. As shown for PEPT1, β-klotho protein decreased significantly the maximal transport rate without significantly modifying the affinity of the carrier. The effect of β-Klotho on PEPT1 was reversed by DSAL. Intestinal IGly was significantly larger in kl-/- than in kl+/+ mice. Conclusion: β-Klotho participates in the regulation of the peptide transporters PEPT1 and PEPT2.

scholarly journals ORMDL1 is upregulated and associated with favorable outcome in colorectal cancer

2020 ◽  
Author(s):  
Qian Wang ◽  
Wanjun Liu ◽  
Si Chen ◽  
Qianxin Luo ◽  
Yichen Li ◽  
...  
Keyword(s):  
Colorectal Cancer ◽  
Cell Proliferation ◽  
Colony Formation ◽  
Transmembrane Protein ◽  
Cohort Analysis ◽  
Negative Regulator ◽  
Morphologic Change ◽  
Mesenchymal Transition

AbstractBackgroundORMDL1 gene encodes a transmembrane protein for endoplasmic reticulum and is known as crucial negative regulator for sphingolipid biogenesis. However, it has been rarely studied in tumor-related context. Therefore, its prognostic value and functional significance in colorectal cancer (CRC) remain to be explored.MethodsTCGA CRC cohort analysis, qRT-PCR, and immunohistochemistry (IHC) were used to examine the ORMDL1 expression level. The association between ORMDL1 expression and various clinical characteristics were analyzed by Chi-square tests. CRC patients’ overall survival (OS) was analyzed by Kaplan-Meier analysis. In vitro and in vivo cell-based assays were performed to explore the role of ORMDL1 in cell proliferation, invasion and migration. Transcriptional changes of cells either with ORMDL1 knockdowned or overexpressed were compared and analyzed.ResultsORMDL1 was upregulated in CRC tissues either in TCGA cohort or in our cohort. Interestingly, its expression was significantly lower in patients with metastasis compared to patients without metastasis, and high expression group had longer OS than low expression group. Knockdown of ORMDL1 expression can promote proliferation, colony formation and invasion, while attenuate migration in CRC cell lines. In opposite, forced overexpression of ORMDL1 reduced cell proliferation, colony formation and invasion, while enhanced cell migration. Epithelial-to-mesenchymal transition (EMT) related genes were enriched among differentially expressed genes when ORMDL1 was knockdowned in cells, which was consistent with morphologic change by microscopy observation. Finally, stable knockdown of ORMDL1 can promote cancer cell proliferation in vivo to some extent.ConclusionORMDL1 is upregulated and may serve as biomarker to predict favourable outcome in colorectal cancer.

scholarly journals Desert Hedgehog-driven endothelium integrity is enhanced by Gas1 but negatively regulated by Cdon

2020 ◽  
Author(s):  
Candice Chapouly ◽  
Pierre-Louis Hollier ◽  
Sarah Guimbal ◽  
Lauriane Cornuault ◽  
Alain-Pierre Gadeau ◽  
...  
Keyword(s):  
Brain Cortex ◽  
Molecular Level ◽  
Negative Regulator ◽  
The Past ◽  
Inflammatory Conditions ◽  
Downstream Effector ◽  
Desert Hedgehog ◽  
Vessel Integrity ◽  
Endothelial Junction ◽  
The Brain

AbstractEvidences accumulated within the past decades, identified Hedgehog (Hh) signaling as a new regulator of micro-vessel integrity. More specifically, we recently identified Desert Hedgehog (Dhh) as a downstream effector of Klf2 in endothelial cells (ECs).ObjectiveThe purpose of this study is to investigate whether Hh co-receptors Gas1 and Cdon may be used as therapeutic targets to modulate Dhh signaling in ECs.Methods and resultsWe demonstrated that both Gas1 and Cdon are expressed in adult ECs and relied on either siRNAs or EC specific conditional KO mice to investigate their role. We found that Gas1 deficiency mainly photocopies Dhh deficiency especially by inducing VCAM-1 and ICAM-1 overexpression while Cdon deficiency has opposite effects by promoting endothelial junction integrity. At a molecular level, Cdon prevents Dhh binding to Ptch1 and thus acts a decoy receptor for Dhh, while Gas1 promotes Dhh binding to Smo and as a result potentiates Dhh effects. Since Cdon is overexpressed in ECs treated by inflammatory cytokines including TNFα and Il1β, we then tested whether Cdon inhibition would promote endothelium integrity in acute inflammatory conditions and found that both fibrinogen and IgG extravasation were decreased in association with an increased Cdh5 expression in the brain cortex of EC specific Cdon KO mice administered locally with Il1β.ConclusionAltogether these results demonstrate that Gas1 is a positive regulator of Dhh in ECs while Cdon is a negative regulator. Interestingly Cdon blocking molecules may then be used to promote endothelium integrity at least in inflammatory conditions.

Downregulation of Klotho expression by dehydration

2011 ◽  
Vol 301 (4) ◽  
pp. F745-F750 ◽  
Author(s):  
Cai Tang ◽  
Ganesh Pathare ◽  
Diana Michael ◽  
Abul Fajol ◽  
Melanie Eichenmüller ◽  
...  
Keyword(s):  
Transmembrane Protein ◽  
Accelerated Aging ◽  
Early Death ◽  
Renal Tissue ◽  
Hek293 Cells ◽  
Protein Abundance ◽  
Transcript Levels ◽  
Age Related ◽  
Klotho Protein ◽  
Growth Deficit

Klotho, a transmembrane protein, protease, and hormone mainly expressed in renal tissue counteracts aging. Overexpression of Klotho substantially prolongs the life span. Klotho deficiency leads to excessive formation of 1,25(OH)2D3, growth deficit, accelerated aging, and early death. Aging is frequently paralleled by dehydration, which is considered to accelerate the development of age-related disorders. The present study explored the possibility that dehydration influences Klotho expression. Klotho transcript levels were determined by RT-PCR, and Klotho protein abundance was detected by Western blotting in renal tissue from hydrated and 36-h-dehydrated mice as well as in human embryonic kidney (HEK293) cells. Dehydration was followed by a significant decline of renal Klotho transcript levels and protein abundance, accompanied by an increase in plasma osmolarity as well as plasma ADH, aldosterone, and 1,25(OH)2D3 levels. Antidiuretic hormone (ADH; 50 nM) and aldosterone (1 μM) significantly decreased Klotho transcription and protein expression in HEK293 cells. In conclusion, the present observations disclose a powerful effect of dehydration on Klotho expression, an effect at least partially mediated by enhanced release of ADH and aldosterone.

WNK4 kinase is a negative regulator of K+-Cl− cotransporters

2007 ◽  
Vol 292 (4) ◽  
pp. F1197-F1207 ◽  
Author(s):  
Tomas Garzón-Muvdi ◽  
Diana Pacheco-Alvarez ◽  
Kenneth B. E. Gagnon ◽  
Norma Vázquez ◽  
José Ponce-Coria ◽  
...  
Keyword(s):  
Expression System ◽  
Negative Regulator ◽  
Cell Swelling ◽  
Xenopus Laevis Oocytes ◽  
Missense Mutations ◽  
Phosphatase Inhibitors ◽  
Membrane Transport Proteins ◽  
Protein Phosphatase Inhibitors ◽  
Pseudohypoaldosteronism Type Ii ◽  
Wnk Kinases

WNK kinases [with no lysine (K) kinase] are emerging as regulators of several membrane transport proteins in which WNKs act as molecular switches that coordinate the activity of several players. Members of the cation-coupled chloride cotransporters family (solute carrier family number 12) are one of the main targets. WNK3 activates the Na+-driven cotransporters NCC, NKCC1, and NKCC2 and inhibits the K+-driven cotransporters KCC1 to KCC4. WNK4 inhibits the activity of NCC and NKCC1, while in the presence of the STE20-related proline-alanine-rich kinase SPAK activates NKCC1. Nothing is known, however, regarding the effect of WNK4 on the K+-Cl− cotransporters. Using the heterologous expression system of Xenopus laevis oocytes, here we show that WNK4 inhibits the activity of the K+-Cl− cotransporters KCC1, KCC3, and KCC4 under cell swelling, a condition in which these cotransporters are maximally active. The effect of WNK4 requires its catalytic activity because it was lost by the substitution of aspartate 318 for alanine (WNK4-D318A) that renders WNK4 catalytically inactive. In contrast, three different WNK4 missense mutations that cause pseudohypoaldosteronism type II do not affect the WNK4-induced inhibition of KCC4. Finally, we observed that catalytically inactive WNK4-D318A is able to bypass the tonicity requirements for KCC2 and KCC3 activation in isotonic conditions. This effect is enhanced by the presence of catalytically inactive SPAK, was prevented by the presence of protein phosphatase inhibitors, and was not present in KCC1 and KCC4. Our results reveal that WNK4 regulates the activity of the K+-Cl− cotransporters expressed in the kidney.

scholarly journals Shisa7 is a GABAA receptor auxiliary subunit controlling benzodiazepine actions

Science ◽  
2019 ◽  
Vol 366 (6462) ◽  
pp. 246-250 ◽  
Author(s):  
Wenyan Han ◽  
Jun Li ◽  
Kenneth A. Pelkey ◽  
Saurabh Pandey ◽  
Xiumin Chen ◽  
...  
Keyword(s):  
Transmembrane Protein ◽  
Clinical Importance ◽  
Aminobutyric Acid ◽  
Inhibitory Synapses ◽  
Channel Pore ◽  
Auxiliary Subunit ◽  
Deactivation Kinetics ◽  
Acid Type ◽  
Genetic Deletion ◽  
The Brain

The function and pharmacology of γ-aminobutyric acid type A receptors (GABAARs) are of great physiological and clinical importance and have long been thought to be determined by the channel pore–forming subunits. We discovered that Shisa7, a single-passing transmembrane protein, localizes at GABAergic inhibitory synapses and interacts with GABAARs. Shisa7 controls receptor abundance at synapses and speeds up the channel deactivation kinetics. Shisa7 also potently enhances the action of diazepam, a classic benzodiazepine, on GABAARs. Genetic deletion of Shisa7 selectively impairs GABAergic transmission and diminishes the effects of diazepam in mice. Our data indicate that Shisa7 regulates GABAAR trafficking, function, and pharmacology and reveal a previously unknown molecular interaction that modulates benzodiazepine action in the brain.

High-affinity peptide transporter PEPT2 (SLC15A2) of the zebrafish Danio rerio: functional properties, genomic organization, and expression analysis

2006 ◽  
Vol 24 (3) ◽  
pp. 207-217 ◽  
Author(s):  
Alessandro Romano ◽  
Gabor Kottra ◽  
Amilcare Barca ◽  
Natascia Tiso ◽  
Michele Maffia ◽  
...  
Keyword(s):  
Inner Ear ◽  
Functional Properties ◽  
Expressed Sequence Tag ◽  
Peptide Transporter ◽  
Otic Vesicle ◽  
Xenopus Laevis Oocytes ◽  
Functional Relationships ◽  
High Affinity ◽  
Peptide Transporters ◽  
Mrna Tissue Distribution

Solute carrier 15 (SLC15) membrane proteins PEPT1 (SLC15A1) and PEPT2 (SLC15A2) have been described in great detail in mammals. In contrast, information in lower vertebrates is limited. We characterized the functional properties of a novel zebrafish peptide transporter orthologous to mammalian and avian PEPT2, described its gene ( pept2) structure, and determined mRNA tissue distribution. An expressed sequence tag (EST) cDNA (Integrated Molecular Analysis of Gene Expression; IMAGE) corresponding to zebrafish pept2 was completed by inserting a stretch of 75 missing nucleotides in the coding sequence to obtain a 3,238-bp functional clone. The complete open reading frame (ORF) was 2,160 bp and encoded a 719-amino acid protein. Electrophysiological analysis after cRNA injection in Xenopus laevis oocytes suggested that zebrafish PEPT2 is a high-affinity/low-capacity transporter ( K0.5 for glycyl-l-glutamine ∼18 μM at −120 mV and pH 7.5). Zebrafish pept2 gene was 19,435 kb, thus being the shortest vertebrate pept2 fully characterized so far. Also, zebrafish pept2 exhibited 23 exons and 22 introns, whereas human and rodent pept2 genes contain 22 exons and 21 introns only. Zebrafish pept2 mRNA was mainly detected in brain, kidney, gut, and, interestingly, otic vesicle, the embryonic structure that develops into the auditory/vestibular organ, homolog to the higher vertebrate inner ear, of the adult fish. Characterization of zebrafish pept2 will contribute to the investigation of peptide transporters using a well-established genetic model and will allow the elucidation of the evolutionary and functional relationships among vertebrate peptide transporters. Moreover, it can represent a useful marker to screen mutations that affect choroid plexus and inner ear development.

scholarly journals LEFTYA Activates the Epithelial Na+ Channel (ENaC) in Endometrial Cells via Serum and Glucocorticoid Inducible Kinase SGK1

2016 ◽  
Vol 39 (4) ◽  
pp. 1295-1306 ◽  
Author(s):  
Madhuri S. Salker ◽  
Zohreh Hosseinzadeh ◽  
Nour Alowayed ◽  
Ni Zeng ◽  
Anja T. Umbach ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Ussing Chamber ◽  
Endometrial Adenocarcinoma ◽  
Negative Regulator ◽  
Na Channel ◽  
Uterine Receptivity ◽  
Endometrial Cells ◽  
Ishikawa Cells ◽  
Epithelial Na Channel ◽  
Endometrial Epithelial Cells

Background: Serum & glucocorticoid inducible kinase (SGK1) regulates several ion channels, including amiloride sensitive epithelial Na+ channel (ENaC). SGK1 and ENaC in the luminal endometrium epithelium, are critically involved in embryo implantation, although little is known about their regulation. The present study explored whether SGK1 and ENaC are modulated by LEFTYA, a negative regulator of uterine receptivity. Methods: Expression levels were determined by qRT-PCR and Western blotting, ENaC channel activity by whole cell patch clamp and transepithelial current by Ussing chamber experiments. Results: Treatment of Ishikawa cells, an endometrial adenocarcinoma model cell line of endometrial epithelial cells, with LEFTYA rapidly up-regulated SGK1 and ENaC transcript and protein levels. Induction of ENaC in response to LEFTYA was blunted upon co-treatment with the SGK1 inhibitor EMD638683. ENaC levels also significantly upregulated upon expression of a constitutively active, but not a kinase dead, SGK1 mutant in Ishikawa cells. LEFTYA increased amiloride sensitive Na+-currents in Ishikawa cells and amiloride sensitive transepithelial current across the murine endometrium. Furthermore, LEFTYA induced the expression of ENaC in the endometrium of wild-type but not of Sgk1-deficient mice. Conclusions: LEFTYA regulates the expression and activity of ENaC in endometrial epithelial cells via SGK1. Aberrant regulation of SGK1 and ENaC by LEFTYA could contribute to the pathogenesis of unexplained infertility.

scholarly journals Endothelial Claudin

1999 ◽  
Vol 147 (1) ◽  
pp. 185-194 ◽  
Author(s):  
Kazumasa Morita ◽  
Hiroyuki Sasaki ◽  
Mikio Furuse ◽  
Shoichiro Tsukita
Keyword(s):  
Endothelial Cells ◽  
Epithelial Cells ◽  
Blood Vessels ◽  
Polyclonal Antibody ◽  
Polyclonal Antibodies ◽  
Transmembrane Protein ◽  
Velo Cardio Facial Syndrome ◽  
The Brain ◽  
Specific Polyclonal Antibody

Tight junctions (TJs) in endothelial cells are thought to determine vascular permeability. Recently, claudin-1 to -15 were identified as major components of TJ strands. Among these, claudin-5 (also called transmembrane protein deleted in velo-cardio-facial syndrome [TMVCF]) was expressed ubiquitously, even in organs lacking epithelial tissues, suggesting the possible involvement of this claudin species in endothelial TJs. We then obtained a claudin-6–specific polyclonal antibody and a polyclonal antibody that recognized both claudin-5/TMVCF and claudin-6. In the brain and lung, immunofluorescence microscopy with these polyclonal antibodies showed that claudin-5/TMVCF was exclusively concentrated at cell–cell borders of endothelial cells of all segments of blood vessels, but not at those of epithelial cells. Immunoreplica electron microscopy revealed that claudin-5/TMVCF was a component of TJ strands. In contrast, in the kidney, the claudin-5/TMVCF signal was restricted to endothelial cells of arteries, but was undetectable in those of veins and capillaries. In addition, in all other tissues we examined, claudin-5/TMVCF was specifically detected in endothelial cells of some segments of blood vessels, but not in epithelial cells. Furthermore, when claudin-5/TMVCF cDNA was introduced into mouse L fibroblasts, TJ strands were reconstituted that resembled those in endothelial cells in vivo, i.e., the extracellular face–associated TJs. These findings indicated that claudin-5/TMVCF is an endothelial cell–specific component of TJ strands.

Rapid downregulation of the rat glutamine transporter SNAT3 by a caveolin-dependent trafficking mechanism in Xenopus laevis oocytes

2010 ◽  
Vol 299 (5) ◽  
pp. C1047-C1057 ◽  
Author(s):  
Sarojini Balkrishna ◽  
Angelika Bröer ◽  
Alice Kingsland ◽  
Stefan Bröer
Keyword(s):  
Xenopus Laevis ◽  
Dominant Negative ◽  
Monocarboxylate Transporter ◽  
Xenopus Laevis Oocytes ◽  
Independent Manner ◽  
Cultured Astrocytes ◽  
Glutamine Transporter ◽  
Liver And Kidney ◽  
The Brain ◽  
Glutamine Uptake

The glutamine transporter SNAT3 is involved in the uptake and release of glutamine in the brain, liver, and kidney. Substrate transport is accompanied by Na+ cotransport and H+ antiport. In this study, treatment of Xenopus laevis oocytes expressing rat SNAT3 with the phorbol ester PMA resulted in a rapid downregulation of glutamine uptake in less than 20 min. PMA treatment of oocytes coexpressing SNAT3 and the monocarboxylate transporter MCT1 reduced SNAT3 activity only, demonstrating the specificity of the regulatory mechanism. Single or combined mutations of seven putative phosphorylation sites in the SNAT3 sequence did not affect the regulation of SNAT3 by PMA. Expression of an EGFP-SNAT3 fusion protein in oocytes established that the downregulation was caused by the retrieval of the transporter from the plasma membrane. Coexpression of SNAT3 with dominant-negative mutants of dynamin or caveolin revealed that SNAT3 trafficking occurs in a dynamin-independent manner and is influenced by caveolin. Although system N activity was not affected by PMA in cultured astrocytes, a downregulation was observed in HepG2 cells.

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