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Hyun S Lillehoj - One of the best experts on this subject based on the ideXlab platform.

  • expression of flotillin 1 on eimeria tenella sporozoites and its role in host cell invasion
    Journal of Parasitology, 2007
    Co-Authors: E. Del Cacho, Margarita Gallego, Caridad Sanchezacedo, Hyun S Lillehoj
    Abstract:

    Lipid rafts are detergent-resistant, liquid-ordered microdomains in plasma membranes that are enriched in cholesterol and sphingolipids and involved in intracellular signal transduction, membrane trafficking, and Molecular Sorting. In this study, we investigated the possibility that lipid rafts on Eimeria tenella sporozoites may act as platforms for host cell invasion. Flotillin-1, a resident protein of lipid rafts, was identified on E. tenella sporozoites and was prominently expressed at the apex of the cells, a region mediating host cell invasion. Pretreatment of sporozoites with antibody against flotillin-1 blocked parasite invasion. Furthermore, the anticoccidial drug, monensin, disrupted the localization of flotillin-1 within raft structures resulting in loss of invasion. We conclude that Eimeria sporozoites utilize lipid rafts containing flotillin-1 for internalization into host cells.

  • expression of flotillin 1 on eimeria tenella sporozoites and its role in
    2007
    Co-Authors: E. Del Cacho, Margarita Gallego, Caridad Sanchezacedo, Hyun S Lillehoj
    Abstract:

    Lipid rafts are detergent-resistant, liquid-ordered microdomains in plasma membranes that are enriched in cholesterol and sphingolipids and involved in intracellular signal transduction, membrane trafficking, and Molecular Sorting. In this study, we investigated the possibility that lipid rafts on Eimeria tenella sporozoites may act as platforms for host cell invasion. Flotillin-1, a resident protein of lipid rafts, was identified on E. tenella sporozoites and was prominently expressed at the apex of the cells, a region mediating host cell invasion. Pretreatment of sporozoites with antibody against flotillin-1 blocked parasite invasion. Furthermore, the anticoccidial drug, monensin, disrupted the localization of flotillin- 1 within raft structures resulting in loss of invasion. We conclude that Eimeria sporozoites utilize lipid rafts containing flotillin-1 for internalization into host cells.

Lene B Oddershede - One of the best experts on this subject based on the ideXlab platform.

  • direct measurement of heating by optically trapped gold nanoparticles using Molecular Sorting in a lipid bilayer
    Biophysical Journal, 2010
    Co-Authors: Poul Martin Bendix, Nader S S Reihani, Lene B Oddershede
    Abstract:

    Gold nanoparticles have are extremely useful as multi-functional and sensitive probes for investigation and manipulation of biological systems. Particles, as small as tenths of nanometers, can be visualized, optically manipulated, and used as controlled force transducers. Their high absorbance also makes them excellent converters of electromagnetic radiation into thermal energy. If the heating can be quantified it can also be advantageously used to perform controlled thermal treatment. We performed a direct measurement of the heating associated with optical trapping of individual gold nanospheres. A trapped gold nanosphere was embedded in a two dimensional supported gel phase lipid bilayer with incorporated fluorescent molecules which preferentially located, e.g., in the gel phase. Visualization of the melted region gave direct information about the temperature profile around the irradiated particle. The heating is highly dependent on particle size and laser power, with surface temperatures increasing from a few to hundreds of degrees Celcius. This quantification allows for creating controlled and localized temperature gradients which can be utilized for destruction of unwanted biological material such as cancer cells, to create local temperature gradients in lipid bilayers, or for nano-engineering purposes.View Large Image | View Hi-Res Image | Download PowerPoint Slide

Ole G Mouritsen - One of the best experts on this subject based on the ideXlab platform.

  • Molecular Sorting of lipids by bacteriorhodopsin in dilauroylphosphatidylcholine distearoylphosphatidylcholine lipid bilayers
    Biophysical Journal, 1997
    Co-Authors: Fabrice Dumas, M M Sperotto, Mariachantal Lebrun, Jeanfrancois Tocanne, Ole G Mouritsen
    Abstract:

    A combined experimental and theoretical study is performed on binary dilauroylphosphatidylcholine/distearoylphosphatidylcholine (DLPC/DSPC) lipid bilayer membranes incorporating bacteriorhodopsin (BR). The system is designed to investigate the possibility that BR, via a hydrophobic matching principle related to the difference in lipid bilayer hydrophobic thickness and protein hydrophobic length, can perform Molecular Sorting of the lipids at the lipid-protein interface, leading to lipid specificity/selectivity that is controlled solely by physical factors. The study takes advantage of the strongly nonideal mixing behavior of the DLPC/DSPC mixture and the fact that the average lipid acyl-chain length is strongly dependent on temperature, particularly in the main phase transition region. The experiments are based on fluorescence energy transfer techniques using specifically designed lipid analogs that can probe the lipid-protein interface. The theoretical calculations exploit a microscopic Molecular interaction model that embodies the hydrophobic matching as a key parameter. At low temperatures, in the gel-gel coexistence region, experimental and theoretical data consistently indicate that BR is associated with the short-chain lipid DLPC. At moderate temperatures, in the fluid-gel coexistence region, BR remains in the fluid phase, which is mainly composed of short-chain lipid DLPC, but is enriched at the interface between the fluid and gel domains. At high temperatures, in the fluid phase, BR stays in the mixed lipid phase, and the theoretical data suggest a preference of the protein for the long-chain DSPC molecules at the expense of the short-chain DLPC molecules. The combined results of the experiments and the calculations provide evidence that a Molecular Sorting principle is active because of hydrophobic matching and that BR exhibits physical lipid selectivity. The results are discussed in the general context of membrane organization and compartmentalization and in terms of nanometer-scale lipid-domain formation.

Ira Mellman - One of the best experts on this subject based on the ideXlab platform.

  • endocytosis and Molecular Sorting
    Annual Review of Cell and Developmental Biology, 1996
    Co-Authors: Ira Mellman
    Abstract:

    Endocytosis in eukaryotic cells is characterized by the continuous and regulated formation of prolific numbers of membrane vesicles at the plasma membrane. These vesicles come in several different varieties, ranging from the actin-dependent formation of phagosomes involved in particle uptake, to smaller clathrin-coated vesicles responsible for the internalization of extracellular fluid and receptor-bound ligands. In general, each of these vesicle types results in the delivery of their contents to lysosomes for degradation. The membrane components of endocytic vesicles, on the other hand, are subject to a series of highly complex and iterative Molecular Sorting events resulting in their targeting to specific destinations. In recent years, much has been learned about the function of the endocytic pathway and the mechanisms responsible for the Molecular Sorting of proteins and lipids. This review attempts to integrate these new concepts with long-established views of endocytosis to present a more coherent picture of how the endocytic pathway is organized and how the intracellular transport of internalized membrane components is controlled. Of particular importance are emerging concepts concerning the protein-based signals responsible for Molecular Sorting and the cytosolic complexes responsible for the decoding of these signals.

  • mechanisms of cell polarity Sorting and transport in epithelial cells
    Current Opinion in Cell Biology, 1994
    Co-Authors: Karl Matter, Ira Mellman
    Abstract:

    The recent discovery of widely distributed targeting determinants, which govern the polarized cell-surface distribution of plasma membrane proteins in epithelial cells, has significantly changed our view of how polarized cells generate functionally distinct membrane domains. Together with the surprising finding that the same determinants are recognized on both the biosynthetic and the endocytic pathways, it now appears likely that a common epigenetic code may exist that controls Molecular Sorting of membrane proteins in a wide variety of polarized, and perhaps even non-polarized, cell types.

  • Molecular Sorting in polarized and non polarized cells common problems common solutions
    Journal of Cell Science, 1993
    Co-Authors: Ira Mellman, Ellen Yamamoto, J A Whitney, Min Kim, Walter Hunziker, Karl Matter
    Abstract:

    We have been interested in determining how epithelial cells generate and maintain their characteristically polarized distributions of membrane proteins. Our efforts to date strongly indicate that the polarized transport in MDCK cells may be due to a set of discrete targeting determinants often found on a membrane protein's cytoplasmic domain. Surprisingly, these determinants are widely distributed and are not specific to proteins expressed in polarized cells. They also appear to function in controlling polarized transport along both the biosynthetic and the endocytic (or transcytotic) pathways. Signals for basolateral transport have been characterized and, like the cytoplasmic domain signal used by plasma membrane receptors for accumulation at clathrin-coated pits, they often involve a critical tyrosine residue. Although the basolateral and coated pit signals may also be co-linear, they are not identical. The basolateral and apical transport determinants are also hierarchically arranged. Although a single protein may contain one or more signals specifying basolateral transport, inactivation of these signals appears to reveal a determinant that directs efficient apical transport. Given that the sequence determinants responsible for polarized transport are not restricted to epithelial cells and are related to determinants commonly utilized in all cells, it is possible that non-polarized cells contain cognate apical and basolateral pathways that are responsible for 'constitutive' transport from the Golgi to the plasma membrane. The presence of two cognate pathways might confer a high degree of plasticity to pre-differentiated cells, allowing them rapidly to begin assuming a polarized phenotype in response to extracellular stimuli without requiring the synthesis of epithelial cell-specific transport machinery.

Poul Martin Bendix - One of the best experts on this subject based on the ideXlab platform.

  • direct measurement of heating by optically trapped gold nanoparticles using Molecular Sorting in a lipid bilayer
    Biophysical Journal, 2010
    Co-Authors: Poul Martin Bendix, Nader S S Reihani, Lene B Oddershede
    Abstract:

    Gold nanoparticles have are extremely useful as multi-functional and sensitive probes for investigation and manipulation of biological systems. Particles, as small as tenths of nanometers, can be visualized, optically manipulated, and used as controlled force transducers. Their high absorbance also makes them excellent converters of electromagnetic radiation into thermal energy. If the heating can be quantified it can also be advantageously used to perform controlled thermal treatment. We performed a direct measurement of the heating associated with optical trapping of individual gold nanospheres. A trapped gold nanosphere was embedded in a two dimensional supported gel phase lipid bilayer with incorporated fluorescent molecules which preferentially located, e.g., in the gel phase. Visualization of the melted region gave direct information about the temperature profile around the irradiated particle. The heating is highly dependent on particle size and laser power, with surface temperatures increasing from a few to hundreds of degrees Celcius. This quantification allows for creating controlled and localized temperature gradients which can be utilized for destruction of unwanted biological material such as cancer cells, to create local temperature gradients in lipid bilayers, or for nano-engineering purposes.View Large Image | View Hi-Res Image | Download PowerPoint Slide