scholarly journals Tau and Membranes: Interactions That Promote Folding and Condensation

2021 ◽  
Vol 9 ◽  
Author(s):  
Chad A. Sallaberry ◽  
Barbie J. Voss ◽  
Jaroslaw Majewski ◽  
Jacek Biernat ◽  
Eckhard Mandelkow ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Phase Separation ◽  
Electrostatic Interactions ◽  
Membrane Surface ◽  
Cellular Functions ◽  
Cell Transport ◽  
Repeat Domain ◽  
A Site ◽  
Β Sheet ◽  
Powerful Mechanism

Tau misfolding and assembly is linked to a number of neurodegenerative diseases collectively described as tauopathies, including Alzheimer’s disease (AD) and Parkinson’s disease. Anionic cellular membranes, such as the cytosolic leaflet of the plasma membrane, are sites that concentrate and neutralize tau, primarily due to electrostatic interactions with tau’s microtubule binding repeat domain (RD). In addition to electrostatic interactions with lipids, tau also has interactions with membrane proteins, which are important for tau’s cellular functions. Tau also interacts with lipid tails to facilitate direct translocation across the membrane and can form stable protein-lipid complexes involved in cell-to-cell transport. Concentrated tau monomers at the membrane surface can form reversible condensates, change secondary structures, and induce oligomers, which may eventually undergo irreversible crosslinking and fibril formation. These β-sheet rich tau structures are capable of disrupting membrane organization and are toxic in cell-based assays. Given the evidence for relevant membrane-based tau assembly, we review the emerging hypothesis that polyanionic membranes may serve as a site for phase-separated tau condensation. Membrane-mediated phase separation may have important implications for regulating tau folding/misfolding, and may be a powerful mechanism to spatially direct tau for native membrane-mediated functions.

scholarly journals Lipid anchoring and electrostatic interactions target the phospholipase NOT-LIKE-DAD to pollen endo-plasma membrane

2020 ◽  
Author(s):  
Laurine M. Gilles ◽  
Veronica La Padula ◽  
Nathanaël M.A. Jacquier ◽  
Jean-Pierre Martinant ◽  
Peter M. Rogowsky ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Electrostatic Interactions ◽  
Membrane Surface ◽  
Male Gamete ◽  
Targeted Mutagenesis ◽  
Major Constituent ◽  
Sperm Cells ◽  
Wild Type Female ◽  
Haploid Embryos ◽  
Membrane Surface Charge

AbstractPhospholipases are ubiquitous enzymes that cleave phospholipids, one major constituent of membranes. They are thus essential for many developmental processes, including male gamete development. In flowering plants, mutation of phospholipase NOT-LIKE-DAD (NLD) leads to peculiar defects in sexual reproduction. Indeed, pollination of a wild-type female with mutant pollen generates haploid embryos containing solely maternal genetic information. Contrary to previous reports NLD does not localize to cytosol and plasma membrane (PM) of sperm cells but to the pollen endo-plasma membrane (endo-PM), a specific membrane derived from the PM of the pollen vegetative cell that encircles the two sperm cells. Pharmacological approaches coupled with targeted mutagenesis revealed that lipid anchoring together with electrostatic interactions between membrane and NLD are involved in the attachment of NLD to this atypical endo-PM. Membrane surface-charge and anionic lipid bio-sensors indicated that phosphatidylinositol-4,5-bisphosphate (PIP(4,5)P2) is enriched in the endo-PM as compared to the PM. Our results uncover a unique example of how membrane electrostatic properties can specify a unique polar domain (i.e. endo-PM), which is critical for plant reproduction and gamete formation.

Lipid anchoring and electrostatic interactions target NOT-LIKE-DAD to pollen endo-plasma membrane

2021 ◽  
Vol 220 (10) ◽  
Author(s):  
Laurine M. Gilles ◽  
Andrea R.M. Calhau ◽  
Veronica La Padula ◽  
Nathanaël M.A. Jacquier ◽  
Claire Lionnet ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Electrostatic Interactions ◽  
Membrane Surface ◽  
Male Gamete ◽  
Targeted Mutagenesis ◽  
Sperm Cells ◽  
Apical Region ◽  
Haploid Embryos ◽  
Membrane Surface Charge ◽  
Specific Membrane

Phospholipases cleave phospholipids, major membrane constituents. They are thus essential for many developmental processes, including male gamete development. In flowering plants, mutation of phospholipase NOT-LIKE-DAD (NLD, also known as MTL or ZmPLA1) leads to peculiar defects in sexual reproduction, notably the induction of maternal haploid embryos. Contrary to previous reports, NLD does not localize to cytosol and plasma membrane of sperm cells but to the pollen endo-plasma membrane (endo-PM), a specific membrane derived from the PM of the pollen vegetative cell that encircles the two sperm cells. After pollen tube burst, NLD localizes at the apical region of the egg apparatus. Pharmacological approaches coupled with targeted mutagenesis revealed that lipid anchoring together with electrostatic interactions are involved in the attachment of NLD to this atypical endo-PM. Membrane surface-charge and lipid biosensors indicated that phosphatidylinositol-4,5-bisphosphate is enriched in the endo-PM, uncovering a unique example of how membrane electrostatic properties can define a specific polar domain (i.e., endo-PM), which is critical for plant reproduction and gamete formation.

scholarly journals Characterization of micron-scale protein-depleted plasma membrane domains in phosphatidylserine-deficient yeast cells

2021 ◽  
Vol 135 (5) ◽  
Author(s):  
Tetsuo Mioka ◽  
Tian Guo ◽  
Shiyao Wang ◽  
Takuma Tsuji ◽  
Takuma Kishimoto ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Phase Separation ◽  
Large Scale ◽  
Living Cells ◽  
Yeast Cells ◽  
Membrane Domain ◽  
Cellular Functions ◽  
Artificial Membranes ◽  
Yeast Mutants

ABSTRACT Membrane phase separation to form micron-scale domains of lipids and proteins occurs in artificial membranes; however, a similar large-scale phase separation has not been reported in the plasma membrane of the living cells. We show here that a stable micron-scale protein-depleted region is generated in the plasma membrane of yeast mutants lacking phosphatidylserine at high temperatures. We named this region the ‘void zone’. Transmembrane proteins and certain peripheral membrane proteins and phospholipids are excluded from the void zone. The void zone is rich in ergosterol, and requires ergosterol and sphingolipids for its formation. Such properties are also found in the cholesterol-enriched domains of phase-separated artificial membranes, but the void zone is a novel membrane domain that requires energy and various cellular functions for its formation. The formation of the void zone indicates that the plasma membrane in living cells has the potential to undergo phase separation with certain lipid compositions. We also found that void zones were frequently in contact with vacuoles, in which a membrane domain was also formed at the contact site.

scholarly journals Lipid membrane templated misfolding and self-assembly of intrinsically disordered tau protein

2020 ◽  
Author(s):  
Jaroslaw Majewski ◽  
Emmalee M. Jones ◽  
Crystal M. Vander Zanden ◽  
Jacek Biernat ◽  
Eckhard Mandelkow ◽  
...  
Keyword(s):  
Phase Separation ◽  
Tau Protein ◽  
Self Assembly ◽  
Electrostatic Interactions ◽  
Lipid Membrane ◽  
Tau Proteins ◽  
Lipid Monolayer ◽  
Intrinsically Disordered ◽  
Tau Aggregation ◽  
Β Sheet

AbstractThe aggregation of the intrinsically disordered tau protein into highly ordered β-sheet fibrils is implicated in many neurodegenerative disorders. Fibrillation mechanism remains unresolved, particularly early events that trigger tau misfolding and assembly. We investigated the role membrane plays in modulating aggregation of three tau variants, the largest isoform hTau40, the truncated construct K18, and a hyperphosphorylation mutant hTau40/3Epi. Despite being charged and soluble, tau proteins were also highly surface active and favorably interacted with anionic, but not zwitterionic, lipid monolayer at the air/water interface. Membrane binding induced macroscopic tau phase separation and β-sheet-rich tau oligomer formation. Concomitantly, membrane morphology and lipid packing became disrupted. Our findings support a general tau aggregation mechanism wherein tau’s inherent surface activity and favorable electrostatic interactions drive tau-membrane association, inducing tau phase separation that is accompanied by misfolding and self-assembly of disordered tau into β-sheet-rich oligomers, which subsequently seed fibrillation and deposition into diseased tissues.

scholarly journals Internalization of Foldamer-Based DNA Mimics through a Site-Specific Antibody Conjugate to Target HER2-Positive Cancer Cells

2021 ◽  
Vol 14 (7) ◽  
pp. 624
Author(s):  
Valentina Corvaglia ◽  
Imène Ait Mohamed Amar ◽  
Véronique Garambois ◽  
Stéphanie Letast ◽  
Aurélie Garcin ◽  
...  
Keyword(s):  
Cancer Cells ◽  
Topoisomerase I ◽  
Ovarian Cancer Cells ◽  
Cellular Functions ◽  
Antibody Drug Conjugate ◽  
Her2 Positive ◽  
Dna Topoisomerase ◽  
Antibody Conjugate ◽  
A Site

Inhibition of protein–DNA interactions represents an attractive strategy to modulate essential cellular functions. We reported the synthesis of unique oligoamide-based foldamers that adopt single helical conformations and mimic the negatively charged phosphate moieties of B-DNA. These mimics alter the activity of DNA interacting enzymes used as targets for cancer treatment, such as DNA topoisomerase I, and they are cytotoxic only in the presence of a transfection agent. The aim of our study was to improve internalization and selective delivery of these highly charged molecules to cancer cells. For this purpose, we synthesized an antibody-drug conjugate (ADC) using a DNA mimic as a payload to specifically target cancer cells overexpressing HER2. We report the bioconjugation of a 16-mer DNA mimic with trastuzumab and its functional validation in breast and ovarian cancer cells expressing various levels of HER2. Binding of the ADC to HER2 increased with the expression of the receptor. The ADC was internalized into cells and was more efficient than trastuzumab at inhibiting their growth in vitro. These results provide proof of concept that it is possible to site-specifically graft high molecular weight payloads such as DNA mimics onto monoclonal antibodies to improve their selective internalization and delivery in cancer cells.

In situ microscopic studies on the structures and phase behaviors of SF/PEG films using solid-state NMR and Raman imaging

2016 ◽  
Vol 18 (24) ◽  
pp. 16353-16360 ◽  
Author(s):  
Congheng Chen ◽  
Ting Yao ◽  
Sidong Tu ◽  
Weijie Xu ◽  
Yi Han ◽  
...  
Keyword(s):  
Phase Separation ◽  
Solid State Nmr ◽  
Random Coil ◽  
Rich Domain ◽  
Microscopic Studies ◽  
Helix Conformation ◽  
Phase Behaviors ◽  
Protein Rich ◽  
Β Sheet

SF was incompatible with PEG in some extent, and the phase separation took place in their blend film. The conformation of SF in the interface between SF and PEG was changed to the β-sheet, while that in the protein-rich domain remained in the random coil and/or helix conformation.

scholarly journals Vacuolar-type H+-ATPase regulates cytoplasmic pH in Toxoplasma gondii tachyzoites

1998 ◽  
Vol 330 (2) ◽  
pp. 853-860 ◽  
Author(s):  
N. J. Silvia MORENO ◽  
Li ZHONG ◽  
Hong-Gang LU ◽  
Wanderley DE SOUZA ◽  
Marlene BENCHIMOL
Keyword(s):  
Plasma Membrane ◽  
Toxoplasma Gondii ◽  
Laser Scanning ◽  
Membrane Surface ◽  
Surface Proteins ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Dependent Manner ◽  
Cytoplasmic Ph ◽  
Bafilomycin A1

Cytoplasmic pH (pHi) regulation was studied in Toxoplasma gondii tachyzoites by using the fluorescent dye 2ʹ,7ʹ-bis-(2-carboxyethyl)-5(6)-carboxyfluorescein. Their mean baseline pHi (7.07±0.06; n = 5) was not significantly affected in the absence of extracellular Na+, K+ or HCO3- but was significantly decreased in a dose-dependent manner by low concentrations of N,Nʹ-dicyclohexylcarbodi-imide (DCCD), N-ethylmaleimide (NEM) or bafilomycin A1. Bafilomycin A1 also inhibited the recovery of tachyzoite pHi after an acid load with sodium propionate. Similar concentrations of DCCD, NEM and bafilomycin A1 produced depolarization of the plasma membrane potential as measured with bis-(1,3-diethylthiobarbituric)trimethineoxonol (bisoxonol), and DCCD prevented the hyperpolarization that accompanies acid extrusion after the addition of propionate, in agreement with the electrogenic nature of this pump. Confocal laser scanning microscopy indicated that, in addition to being located in cytoplasmic vacuoles, the vacuolar (V)-H+-ATPase of T. gondii tachyzoites is also located in the plasma membrane. Surface localization of the V-H+-ATPase was confirmed by experiments using biotinylation of cell surface proteins and immunoprecipitation with antibodies against V-H+-ATPases. Taken together, the results are consistent with the presence of a functional V-H+-ATPase in the plasma membrane of these intracellular parasites and with an important role of this enzyme in the regulation of pHi homoeostasis in these cells.

Liposomes with cerasome-forming lipids as gene therapy vectors

2021 ◽  
Author(s):  
Moataz Dowaidar
Keyword(s):  
Electrostatic Interactions ◽  
Membrane Surface ◽  
Immunological Response ◽  
Basic Research ◽  
Systemic Circulation ◽  
Cationic Lipids ◽  
Transport Systems ◽  
Component Selection ◽  
Polar Groups ◽  
Gene Therapy Vectors

Basic research focuses on liposome transport systems as non-viral ways of transferring genetic and therapeutic substances. Due to electrostatic interactions between positive polar groups of cationic lipids and the negatively charged cell membrane surface, nucleic acids may readily be transported into cells as part of lipoplexes. Cationic liposomes, however, have a number of well-known problems, including low stability, toxicity, and a potential for severe immunological response. Recent research has revealed, however, that by increasing the system with additional components such as cerasome-forming lipids, these problems may be solved. They aid in the prolongation of the release of a beneficial liposome load in cells by increasing vesicle stability in the systemic circulation. This circumstance broadens the applications for liposomal systems. As a consequence, using varied lipids can create numerous liposomes for use in a range of medical fields. Nonviral delivery approaches based on hybrid liposomes with suitable structural component selection may be a possible response to a number of medical concerns, and further study is urgently needed.

Lipocortin 1 (annexin 1) in patches associated with the membrane of a lung adenocarcinoma cell line and in the cell cytoplasm

1998 ◽  
Vol 111 (10) ◽  
pp. 1405-1418 ◽  
Author(s):  
V. Traverso ◽  
J.F. Morris ◽  
R.J. Flower ◽  
J. Buckingham
Keyword(s):  
Plasma Membrane ◽  
Membrane Protein ◽  
Lung Adenocarcinoma ◽  
Western Blotting ◽  
Signal Sequence ◽  
Membrane Surface ◽  
Integral Membrane Protein ◽  
Subcellular Fractionation ◽  
Cell Fractionation ◽  
Electron Microscopic

Lipocortin 1 (annexin I) is a calcium- and phospholipid-binding annexin protein which can be externalised from cells despite the lack of a signal sequence. To determine its cellular distribution lipocortin 1 in A549 human lung adenocarcinoma cells was localised by light- and electron-microscopic immunocytochemistry and by cell fractionation and western blotting. Lipocortin 1 immunoreactivity is concentrated in prominent patches associated with the plasma membrane. The intensity of these patches varied with the confluence and duration of the culture and was not detectably diminished by an EDTA wash before fixation. Tubulin and cytokeratin 8 were colocalized with lipocortin 1 in the patches. Within the cells lipocortin 1 was distributed throughout the cytoplasm. Electron microscopy revealed prominent immunoreactivity along the plasma membrane with occasional large clusters of gold particles in contact with the membrane surface of the cells; within the cytoplasm the membrane of some vesicle/vacuole structures and some small electron-dense bodies was immunoreactive, but no immunogold particles were associated with the multilamellar bodies. Subcellular fractionation, extraction and western blotting showed that lipocortin 1 in the membrane pellet was present as two distinct fractions; one, intimately associated with the lipid bilayer, which behaved like an integral membrane protein and one loosely attached which behaved like a peripheral membrane protein. The results show that a substantial amounts of lipocortin 1 is concentrated in focal structures associated with and immediately beneath the plasma membrane. These might form part of the mechanism by which lipocortin 1 is released from the cells.

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