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John R. Silvius

Bio: John R. Silvius is an academic researcher from McGill University. The author has contributed to research in topics: Lipid bilayer & Vesicle. The author has an hindex of 49, co-authored 95 publications receiving 7607 citations.


Papers
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Journal ArticleDOI
11 Jan 2008-Science
TL;DR: A biosensor developed to study the subcellular distribution of phosphatidylserine found that it binds the cytosolic leaflets of the plasma membrane, as well as endosomes and lysosomes.
Abstract: Electrostatic interactions with negatively charged membranes contribute to the subcellular targeting of proteins with polybasic clusters or cationic domains. Although the anionic phospholipid phosphatidylserine is comparatively abundant, its contribution to the surface charge of individual cellular membranes is unknown, partly because of the lack of reagents to analyze its distribution in intact cells. We developed a biosensor to study the subcellular distribution of phosphatidylserine and found that it binds the cytosolic leaflets of the plasma membrane, as well as endosomes and lysosomes. The negative charge associated with the presence of phosphatidylserine directed proteins with moderately positive charge to the endocytic pathway. More strongly cationic proteins, normally associated with the plasma membrane, relocalized to endocytic compartments when the plasma membrane surface charge decreased on calcium influx.

945 citations

Journal ArticleDOI
TL;DR: Evidence that cholesterol interacts differentially with different membrane lipids, associating particularly strongly with saturated, high-melting phospho- and sphingolipids and particularly weakly with highly unsaturated lipid species is considered.

550 citations

Journal ArticleDOI
TL;DR: Fluorescent analogues of two of the diacylglycerol-based cationic amphiphiles examined in this study are shown to be readily degraded after incorporation into CV-1 cells from PE/cationic lipid dispersions.

486 citations

Journal ArticleDOI
TL;DR: PE/DOTAP vesicles show substantial lipid mixing with negatively charged vesicle containing high proportions of phosphatidylcholine, as well as with human erythrocyte ghosts, on a time scale of a few minutes.
Abstract: Lipid vesicles with a positive surface charge have been prepared by using mixtures of phosphatidylethanolamine (PE) and phosphatidylcholine (PC) together with low mole fractions of a cationic lipid analogue, 1,2-bis(oleoyloxy)-3-(trimethylammonio)propane (DOTAP). We have used measurements of vesicle aggregation, lipid mixing, contents mixing, and contents leakage to examine the interactions between these vesicles and similar vesicles that carry a negative surface charge. Mixtures of vesicles with opposite surface charges aggregate readily at physiological or lower ionic strengths, and the extent of this aggregation is enhanced for vesicles that contain high proportions of PE relative to PC. Mixing of lipids and aqueous contents can also be observed between such vesicles, particularly when the vesicles contain substantial proportions of PE. Surprisingly, these latter processes are strongly promoted by monovalent salts and do not proceed at very low ionic strengths. PE/DOTAP vesicles show substantial lipid mixing with negatively charged vesicles containing high proportions of phosphatidylcholine, as well as with human erythrocyte ghosts, on a time scale of a few minutes. These interactions are strongly promoted both by the presence of high levels of PE in the cationic vesicles and by the presence of complementary surface charges on the two membrane populations.

339 citations

Journal ArticleDOI
21 Jul 2006-Science
TL;DR: These probes revealed marked, localized alterations in the charge of the inner surface of the plasma membrane of macrophages during the course of phagocytosis, which accounted for the change in surface potential at the phagosomal cup.
Abstract: The surface potential of biological membranes varies according to their lipid composition. We devised genetically encoded probes to assess surface potential in intact cells. These probes revealed marked, localized alterations in the charge of the inner surface of the plasma membrane of macrophages during the course of phagocytosis. Hydrolysis of phosphoinositides and displacement of phosphatidylserine accounted for the change in surface potential at the phagosomal cup. Signaling molecules such as K-Ras, Rac1, and c-Src that are targeted to the membrane by electrostatic interactions were rapidly released from membrane subdomains where the surface charge was altered by lipid remodeling during phagocytosis.

315 citations


Cited by
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Journal ArticleDOI
05 Jun 1997-Nature
TL;DR: A new aspect of cell membrane structure is presented, based on the dynamic clustering of sphingolipids and cholesterol to form rafts that move within the fluid bilayer that function as platforms for the attachment of proteins when membranes are moved around inside the cell and during signal transduction.
Abstract: A new aspect of cell membrane structure is presented, based on the dynamic clustering of sphingolipids and cholesterol to form rafts that move within the fluid bilayer. It is proposed that these rafts function as platforms for the attachment of proteins when membranes are moved around inside the cell and during signal transduction.

9,436 citations

Journal ArticleDOI
TL;DR: How do cells apply anabolic and catabolic enzymes, translocases and transporters, plus the intrinsic physical phase behaviour of lipids and their interactions with membrane proteins, to create the unique compositions and multiple functions of their individual membranes?
Abstract: Throughout the biological world, a 30 A hydrophobic film typically delimits the environments that serve as the margin between life and death for individual cells. Biochemical and biophysical findings have provided a detailed model of the composition and structure of membranes, which includes levels of dynamic organization both across the lipid bilayer (lipid asymmetry) and in the lateral dimension (lipid domains) of membranes. How do cells apply anabolic and catabolic enzymes, translocases and transporters, plus the intrinsic physical phase behaviour of lipids and their interactions with membrane proteins, to create the unique compositions and multiple functionalities of their individual membranes?

5,720 citations

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TL;DR: The relationship between detergent-resistant membranes, rafts, caveolae, and low-density plasma membrane fragments, and possible functions of lipid rafts in membranes are discussed.
Abstract: ▪ Abstract Recent studies showing that detergent-resistant membrane fragments can be isolated from cells suggest that biological membranes are not always in a liquid-crystalline phase. Instead, sph...

2,951 citations

Journal ArticleDOI
TL;DR: What is known about mammalian endocytic mechanisms is reviewed, with focus on the cellular proteins that control these events, and the functional relevance of distinctendocytic pathways is discussed.
Abstract: Endocytic mechanisms control the lipid and protein composition of the plasma membrane, thereby regulating how cells interact with their environments. Here, we review what is known about mammalian endocytic mechanisms, with focus on the cellular proteins that control these events. We discuss the well-studied clathrin-mediated endocytic mechanisms and dissect endocytic pathways that proceed independently of clathrin. These clathrin-independent pathways include the CLIC/GEEC endocytic pathway, arf6-dependent endocytosis, flotillin-dependent endocytosis, macropinocytosis, circular doral ruffles, phagocytosis, and trans-endocytosis. We also critically review the role of caveolae and caveolin1 in endocytosis. We highlight the roles of lipids, membrane curvature-modulating proteins, small G proteins, actin, and dynamin in endocytic pathways. We discuss the functional relevance of distinct endocytic pathways and emphasize the importance of studying these pathways to understand human disease processes.

2,685 citations

Journal ArticleDOI
TL;DR: This work will review the evidence that rafts exist in cells and focus on their structure, or the organization of raft lipids and proteins, and the role of rafts in signaling in hematopoietic cells.

2,312 citations