scholarly journals Zn2+ triggered two-step mechanism of CLIC1 membrane insertion and activation into chloride channels

2021 ◽  
Author(s):  
Lorena Varela ◽  
Alex C Hendry ◽  
Joseph Cassar ◽  
Ruben Martin-Escolano ◽  
Diego Cantoni ◽  
...  
Keyword(s):  
Chloride Channels ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Molecular Switch ◽  
Soluble Form ◽  
Membrane Insertion ◽  
Dependent Manner ◽  
Intracellular Release ◽  
Proliferation And Metastasis ◽  
Step Mechanism

The CLIC protein family displays the unique feature of altering its structure from a soluble form to a membrane-bound chloride channel. CLIC1, a member of this family, is found in the cytoplasm or in internal and the plasma membranes, with membrane relocalisation linked to endothelial disfunction, tumour proliferation and metastasis. The molecular switch promoting CLIC1 activation remains unclear. Here, cellular chloride efflux assays and immunofluorescence microscopy studies have identified Zn2+ intracellular release as the trigger for CLIC1 activation and membrane relocalisation. Biophysical assays confirmed specific binding to Zn2+, inducing membrane association and enhancing chloride efflux in a pH dependent manner. Together, our results identify a two-step mechanism with Zn2+ binding as the molecular switch promoting CLIC1 membrane insertion, followed by pH activation of chloride efflux.

scholarly journals Membrane insertion of soluble CLIC1 into active chloride channels is triggered by specific divalent cations

2019 ◽  
Author(s):  
Lorena Varela ◽  
Alex C. Hendry ◽  
Encarnacion Medina-Carmona ◽  
Diego Cantoni ◽  
Jose L. Ortega-Roldan
Keyword(s):  
Fluorescence Microscopy ◽  
Chloride Channel ◽  
Chloride Channels ◽  
Molecular Switch ◽  
Solution Nmr ◽  
Soluble Form ◽  
Membrane Insertion ◽  
Nmr Studies ◽  
Channel Form ◽  
Membrane Bound

ABSTRACTThe CLIC family of proteins display the unique feature of altering their structure from a soluble form to a membrane-bound chloride channel. CLIC1, a member of this family, can be found in the cytoplasm or in nuclear, ER and plasma membranes, with membrane overexpression linked to tumour proliferation. The molecular switch promoting CLIC1 membrane insertion has been related to environmental factors, but still remains unclear. Here, we use solution NMR studies to confirm that both the soluble and membrane bound forms are in the same oxidation state. Our data from fluorescence assays and chloride efflux assays indicate that Ca2+and Zn2+trigger association to the membrane into active chloride channels. We use fluorescence microscopy to confirm that an increase of the intracellular Ca2+leads to re-localisation of CLIC1 to both plasma and internal membranes. Finally, we show that soluble CLIC1 adopts an equilibrium of oligomeric species, and Ca2+/Zn2+mediated membrane insertion promotes the formation of a tetrameric assembly. Thus, our results identify Ca2+and Zn2+binding as the molecular switch promoting CLIC1 membrane insertion.SIGNIFICANCE STATEMENTCLIC1, a member of the CLIC family of proteins, is expressed as a soluble protein in cells but can insert in the membrane forming a chloride channel. This chloride channel form is upregulated in different types of cancers including glioblastoma and promote tumour invasiveness and metastasis. The factors promoting CLIC1 membrane insertion nor the mechanism of this process are yet understood. Here, we use a combination of solution NMR, biophysics and fluorescence microscopy to identify Ca2+and Zn2+binding as the switch to promote CLIC1 insertion into the membrane to form active chloride channels. We also provide a simple mechanism how such transition to the membrane occurs. Such understanding will enable subsequent studies on the structure of the chloride channel form and its inhibition.

Enhanced binding of low and high density lipoproteins to human adipocyte plasma membranes: effects of temperature and proteases

1986 ◽  
Vol 64 (12) ◽  
pp. 1378-1382
Author(s):  
Bessie S. Fong ◽  
Pedro O. Rodrigues ◽  
Aubie Angel
Keyword(s):  
Plasma Membranes ◽  
Specific Binding ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
High Density ◽  
High Density Lipoproteins ◽  
Dependent Manner ◽  
Human Adipocyte ◽  
Ldl Binding ◽  
Adipocyte Plasma Membranes

The specific binding of 125I-labelled low density lipoprotein ([125I]LDL to human adipocyte plasma membranes was higher at 37 than at 0 °C. Prior treatment of membranes with pronase had no effect on LDL binding measured at 0 °C but consistently stimulated binding at 37 °C. Plasmin was similar to pronase in enhancing LDL-specific binding, but thrombin was not as effective. 125I-labelled high density lipoprotein ([125I]HDL2) specific binding to human adipocyte plasma membranes was similarly sensitive to temperature and pronase treatment. Addition of the protease inhibitor aprotinin in the adipocyte membrane binding assay significantly reduced [125I]LDL binding at 37 °C (p < 0.05), suggesting the involvement of a protease activity intrinsic to the lipoproteins and (or) membranes. These data demonstrate that both LDL and HDL binding in human adipocyte plasma membranes can be "up-regulated" by specific proteolytic perturbations in a temperature-dependent manner.

scholarly journals Synthetic design of farnesyl-electrostatic peptides for development of a protein kinase A membrane translocation switch

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Allen K. Kim ◽  
Helen D. Wu ◽  
Takanari Inoue
Keyword(s):  
Protein Kinase ◽  
Protein Kinase A ◽  
Single Molecule ◽  
Plasma Membranes ◽  
Modular Design ◽  
Molecular Switch ◽  
Dependent Manner ◽  
Sensors And Actuators ◽  
Kinase A ◽  
In Cells

AbstractMolecular switches that respond to a biochemical stimulus in cells have proven utility as a foundation for developing molecular sensors and actuators that could be used to address important biological questions. Developing a molecular switch unfortunately remains difficult as it requires elaborate coordination of sensing and actuation mechanisms built into a single molecule. Here, we rationally designed a molecular switch that changes its subcellular localization in response to an intended stimulus such as an activator of protein kinase A (PKA). By arranging the sequence for Kemptide in tandem, we designed a farnesylated peptide whose localization can dramatically change upon phosphorylation by PKA. After testing a different valence number of Kemptide as well as modulating the linker sequence connecting them, we identified an efficient peptide switch that exhibited dynamic translocation between plasma membranes and internal endomembranes in a PKA activity dependent manner. Due to the modular design and small size, our PKA switch can have versatile utility in future studies as a platform for visualizing and perturbing signal transduction pathways, as well as for performing synthetic operations in cells.

scholarly journals Human Articular Chondrocytes Induce Interleukin-2 Nonresponsiveness to Allogeneic Lymphocytes

Cartilage ◽  
2016 ◽  
Vol 8 (3) ◽  
pp. 300-306 ◽  
Author(s):  
Satomi Abe ◽  
Hitoshi Nochi ◽  
Hiroshi Ito
Keyword(s):  
T Cells ◽  
Articular Chondrocytes ◽  
Interleukin 2 ◽  
Flow Cytometric Analysis ◽  
Third Party ◽  
Soluble Form ◽  
Enzyme Linked Immunosorbent Assay ◽  
Dependent Manner ◽  
Activated T Cells ◽  
Allogeneic Lymphocytes

Introduction We previously showed that articular chondrocytes (ACs) have immune privilege and immunomodulatory functions like those of mesenchymal stem cells. To elucidate these mechanisms, we focused on interleukin-2 (IL-2), which plays critical roles in lymphocyte mitogenic activity. The purpose of this study was to explore whether ACs affect the role of IL-2 underlying immunomodulatory functions. Material and Methods Irradiated human ACs from osteoarthritis donors were used. Third-party ACs were added to the mixed lymphocyte reaction (MLR) with or without recombinant human IL-2 (rhIL-2), and the levels of IL-2 and the soluble form of the IL-2 receptor α (sIL-2Rα) protein in supernatant were measured by enzyme-linked immunosorbent assay. Recombinant human IL-2 (rhIL-2) was also added to the MLR. To detect the expression of IL-2 receptor α (CD25) on lymphocytes in the MLR, flow cytometric analysis was performed. Last, ACs and allogeneic activated CD4+ T cell were co-cultured, and the expression of CD25 on activated T cells was examined by flow cytometry. Results Third-party ACs significantly inhibited the MLR and reduced the level of sIL-2Rα in a dose-dependent manner, but did not affect the concentration of IL-2. Exogenous rhIL-2 accelerated MLR but did not rescue the inhibitory effect of ACs. ACs inhibited the expression of CD25 on activated CD4+ T cells. Discussion Our results showed that third-party ACs inhibited the proliferation of allogeneic activated lymphocytes, thereby inhibiting production sIL-2Rα, although ACs did not affect IL-2 secretion from lymphocytes. Also, ACs inhibited CD25 expression on activated CD4+ T cells. Thus, ACs inhibited the immune response of allogeneic lymphocytes by inducing IL-2 nonresponsiveness.

scholarly journals Purification and characterization of a major glycoprotein in rat hepatoma plasma membranes. One of the membrane proteins released by phosphatidylinositol-specific phospholipase C

1987 ◽  
Vol 241 (1) ◽  
pp. 63-70 ◽  
Author(s):  
Y Ikehara ◽  
Y Hayashi ◽  
S Ogata ◽  
A Miki ◽  
T Kominami
Keyword(s):  
Alkaline Phosphatase ◽  
Phospholipase C ◽  
Plasma Membranes ◽  
Polyacrylamide Gel Electrophoresis ◽  
Gel Filtration ◽  
Soluble Form ◽  
Microsomal Membranes ◽  
Hydrophobic Nature ◽  
Rat Hepatoma

A major glycoprotein of rat hepatoma plasma membranes was selectively released as a soluble form by incubating the membrane with phosphatidylinositol-specific phospholipase C. The soluble form corresponding to the glycoprotein was also prepared by butan-1-ol extraction of microsomal membranes at pH 5.5, whereas extraction at pH 8.5 yielded an electrophoretically different form with a hydrophobic nature. The soluble glycoprotein extracted at pH 5.5 was purified by sequential chromatography on concanavalin A-Sepharose, Sephacryl S-300 and anti-(alkaline phosphatase) IgG-Sepharose, the last step being used to remove a contaminating alkaline phosphatase. The glycoprotein thus purified was a single protein with Mr 130,000 in SDS/polyacrylamide-gel electrophoresis, although it behaved as a dimer in gel filtration on Sephacryl S-300. The glycoprotein was analysed for amino acid and carbohydrate composition. The composition of the carbohydrate moiety, which amounted to 64% by weight, suggested that the glycoprotein contained much larger numbers of N-linked oligosaccharide chains than those with O-linkage. It was confirmed that the purified glycoprotein was immunologically identical not only with that released by the phospholipase C but also with the hydrophobic form extracted with butan-1-ol at pH 8.5. The results indicate that the glycoprotein of rat hepatoma plasma membranes, which has an unusually high content of carbohydrate, is another membrane protein released by phosphatidylinositol-specific phospholipase C, as documented for alkaline phosphatase, acetylcholinesterase and Thy-1 antigen.

scholarly journals Prospects and Pitfalls of Pregnancy-Associated Malaria Vaccination Based on the Natural Immune Response to Plasmodium falciparum VAR2CSA-Expressing Parasites

2011 ◽  
Vol 2011 ◽  
pp. 1-21 ◽  
Author(s):  
Elizabeth G. Kane ◽  
Andrew W. Taylor-Robinson
Keyword(s):  
Plasmodium Falciparum ◽  
Chondroitin Sulphate ◽  
Specific Binding ◽  
First Trimester ◽  
Effective Vaccine ◽  
Dependent Manner ◽  
Insufficient Information ◽  
Infant Deaths ◽  
Cytokine Balance ◽  
Current Vaccine

Pregnancy-associated malaria, a manifestation of severe malaria, is the cause of up to 200,000 infant deaths a year, through the effects of placental insufficiency leading to growth restriction and preterm delivery. Development of a vaccine is one strategy for control. Plasmodium falciparum-infected red blood cells accumulate in the placenta through specific binding of pregnancy-associated parasite variants that express the VAR2CSA antigen to chondroitin sulphate A on the surface of syncytiotrophoblast cells. Parasite accumulation, accompanied by an inflammatory infiltrate, disrupts the cytokine balance of pregnancy with the potential to cause placental damage and compromise foetal growth. Multigravid women develop immunity towards VAR2CSA-expressing parasites in a gravidity-dependent manner which prevents unfavourable pregnancy outcomes. Although current vaccine design, targeting VAR2CSA antigens, has succeeded in inducing antibodies artificially, this candidate may not provide protection during the first trimester and may only protect those women living in areas endemic for malaria. It is concluded that while insufficient information about placental-parasite interactions is presently available to produce an effective vaccine, incremental progress is being made towards achieving this goal.

Characteristic features of specific binding of pentapeptide HFPGP labeled at the C-terminal proline residue to rat forebrain plasma membranes

2014 ◽  
Vol 456 (1) ◽  
pp. 101-103 ◽  
Author(s):  
T. V. Vyunova ◽  
L. A. Andreeva ◽  
K. V. Shevchenko ◽  
V. P. Shevchenko ◽  
M. Yu. Bobrov ◽  
...  
Keyword(s):  
Plasma Membranes ◽  
Specific Binding ◽  
Proline Residue ◽  
Rat Forebrain ◽  
Characteristic Features

scholarly journals Photoaffinity labelling of a nitrobenzylthioinosine-binding polypeptide from cultured Novikoff hepatoma cells

1986 ◽  
Vol 236 (3) ◽  
pp. 665-670 ◽  
Author(s):  
W P Gati ◽  
J A Belt ◽  
E S Jakobs ◽  
J D Young ◽  
S M Jarvis ◽  
...  
Keyword(s):  
Gel Electrophoresis ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Hepatoma Cells ◽  
Nucleoside Transport ◽  
Facilitated Diffusion ◽  
Animal Cells ◽  
Novikoff Hepatoma

Site-specific binding of nitrobenzylthioinosine (NBMPR) to plasma membranes of some animal cells results in the inhibition of the facilitated diffusion of nucleosides. The present study showed that nucleoside transport in Novikoff UA rat hepatoma cells is insensitive to site-saturating concentrations of NBMPR. Equilibrium binding experiments demonstrated the presence of high-affinity sites for NBMPR in a membrane-enriched fraction from these cells. In the presence of uridine or dipyridamole, specific binding of NBMPR at these sites was inhibited. When Novikoff UA membranes were covalently labelled with [3H]NBMPR by using photoaffinity techniques, specifically bound radioactivity was incorporated exclusively into a polypeptide(s) with an apparent Mr of 72,000-80,000, determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Covalent labelling of this polypeptide was abolished in the presence of excess nitrobenzylthioguanosine (NBTGR) and reduced in the presence of adenosine, uridine or dipyridamole. The apparent Mr of the NBMPR-binding polypeptide in Novikoff UA cells is significantly higher than that reported for corresponding polypeptides in other cell types (Mr 45,000-66,000). When membrane-enriched preparations from S49 mouse lymphoma cells were photolabelled and mixed with labelled NovikoffUA membrane-enriched preparations, gel electrophoresis resolved the NBMPR-binding polypeptides from the two preparations.

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