Selective Association of Cholesterol with Long-Chain Phospholipids in Liquid-Ordered Bilayers:  Support for the Existence of Lipid Rafts

2003 ◽  
Vol 125 (43) ◽  
pp. 13040-13041 ◽  
Author(s):  
Michihiro Sugahara ◽  
Maki Uragami ◽  
Steven L. Regen
Keyword(s):  
Lipid Rafts ◽  
Liquid Ordered ◽  
Long Chain

scholarly journals Uptake of long chain fatty acids is regulated by dynamic interaction of FAT/CD36 with cholesterol/sphingolipid enriched microdomains (lipid rafts)

2008 ◽  
Vol 9 (1) ◽  
Author(s):  
Robert Ehehalt ◽  
Richard Sparla ◽  
Hasan Kulaksiz ◽  
Thomas Herrmann ◽  
Joachim Füllekrug ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Lipid Rafts ◽  
Dynamic Interaction ◽  
Long Chain Fatty Acids ◽  
Long Chain ◽  
Chain Fatty Acids

scholarly journals Lipid rafts and regulation of the cytoskeleton during T cell activation

2005 ◽  
Vol 360 (1461) ◽  
pp. 1663-1672 ◽  
Author(s):  
Karina F Meiri
Keyword(s):  
T Cell ◽  
Lipid Rafts ◽  
T Cell Activation ◽  
Cell Activation ◽  
Immunological Synapse ◽  
Membrane Lipids ◽  
Actin Dynamics ◽  
Associated Proteins ◽  
Liquid Ordered

The ability of polarized cells to initiate and sustain directional responses to extracellular signals is critically dependent on direct communication between spatially organized signalling modules in the membrane and the underlying cytoskeleton. Pioneering work in T cells has shown that the assembly of signalling modules critically depends on the functional compartmentalization of membrane lipids into ordered microdomains or lipid rafts. The significance of rafts in T cell activation lies not only in their ability to recruit the signalling partners that eventually assemble into a mature immunological synapse but also in their ability to regulate actin dynamics and recruit cytoskeletal associated proteins, thereby achieving the structural polarization underlying stability of the synapse—a critical prerequisite for activation to be sustained. Lipid rafts vary quite considerably in size and visualizing the smallest of them in vivo has been challenging. Nonetheless it is now been shown quite convincingly that a surprisingly large proportion—in the order of 50%—of external membrane lipids (chiefly cholesterol and glycosphingolipids) can be dynamically localized in these liquid ordered rafts. Complementary inner leaflet rafts are less well characterized, but contain phosphoinositides as an important functional component that is crucial for regulating the behaviour of the actin cytoskeleton. This paper provides an overview of the interdependency between signalling and cytoskeletal polarization, and in particular considers how regulation of the cytoskeleton plays a crucial role in the consolidation of rafts and their stabilization into the immunological synapse.

scholarly journals Dietary fish oil and DHA down-regulate antigen-activated CD4+T-cells while promoting the formation of liquid-ordered mesodomains

2013 ◽  
Vol 111 (2) ◽  
pp. 254-260 ◽  
Author(s):  
Wooki Kim ◽  
Rola Barhoumi ◽  
David N. McMurray ◽  
Robert S. Chapkin
Keyword(s):  
T Cells ◽  
T Cell ◽  
Transgenic Mice ◽  
Fish Oil ◽  
Lipid Rafts ◽  
T Cell Activation ◽  
Cell Function ◽  
Immunological Synapse ◽  
Potential Contribution ◽  
Liquid Ordered

We have demonstrated previously thatn-3 PUFA endogenously produced byfat-1transgenic mice regulate CD4+T-cell function by affecting the formation of lipid rafts, liquid-ordered mesodomains in the plasma membrane. In the present study, we tested the effects of dietary sources ofn-3 PUFA, i.e. fish oil (FO) or purified DHA, when compared with ann-6 PUFA-enriched maize oil control diet in DO11.10 T-cell receptor transgenic mice. Dietaryn-3 PUFA were enriched in CD4+T-cells, resulting in the increase of then-3:n-6 ratio. Following antigen-specific CD4+T-cell activation by B-lymphoma cells pulsed with the ovalbumin 323–339 peptide, the formation of liquid-ordered mesodomains at the immunological synapse relative to the whole CD4+T-cell, as assessed by Laurdan labelling, was increased (P< 0·05) in the FO-fed group. The FO diet also suppressed (P< 0·05) the co-localisation of PKCθ with ganglioside GM1 (monosialotetrahexosylganglioside), a marker for lipid rafts, which is consistent with previous observations. In contrast, the DHA diet down-regulated (P< 0·05) PKCθ signalling by moderately affecting the membrane liquid order at the immunological synapse, suggesting the potential contribution of the other majorn-3 PUFA components of FO, including EPA.

Lipid microdomains in model and biological membranes: how strong are the connections?

2005 ◽  
Vol 38 (4) ◽  
pp. 373-383 ◽  
Author(s):  
John Silvius
Keyword(s):  
Lipid Rafts ◽  
Model Systems ◽  
Membrane Microdomains ◽  
Potential Importance ◽  
Functional Importance ◽  
Lipid Microdomains ◽  
Membrane Biology ◽  
Liquid Ordered ◽  
Membrane Components ◽  
Membrane Signaling

1. Introduction 3732. Are rafts probable? 3743. Micro-, nano- or ephemeral domains? 3754. How can we reliably assess ‘raft’ composition? 3765. Are rafts plausible? 3796. What more can model systems contribute to ‘raft’ studies? 3817. References 382The concept of ‘lipid rafts’ and related liquid-ordered membrane microdomains has attracted great attention in the field of membrane biology, both as a novel paradigm in models of membrane organization and for the potential importance of such domains in phenomena such as membrane signaling and the differential trafficking of various membrane components. Studies of biological and of model membranes have gone hand in hand in shaping our current picture of the possible organization and functions of liquid-ordered lipid microdomains in membranes. This essay discusses some important current questions concerning the existence and functional importance of lipid microdomains in mammalian cell membranes, and the potential as well as the limitations of using model systems to help to address such questions.

scholarly journals What Can Mushroom Proteins Teach Us about Lipid Rafts?

Membranes ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 264
Author(s):  
Maja Grundner ◽  
Anastasija Panevska ◽  
Kristina Sepčić ◽  
Matej Skočaj
Keyword(s):  
Lipid Rafts ◽  
Lipid Raft ◽  
Mammalian Cells ◽  
Binding Proteins ◽  
Protein Complexes ◽  
Biological Membranes ◽  
Indirect Evidence ◽  
Lipid Binding ◽  
Liquid Ordered

The lipid raft hypothesis emerged as a need to explain the lateral organization and behavior of lipids in the environment of biological membranes. The idea, that lipids segregate in biological membranes to form liquid-disordered and liquid-ordered states, was faced with a challenge: to show that lipid-ordered domains, enriched in sphingomyelin and cholesterol, actually exist in vivo. A great deal of indirect evidence and the use of lipid-binding probes supported this idea, but there was a lack of tools to demonstrate the existence of such domains in living cells. A whole new toolbox had to be invented to biochemically characterize lipid rafts and to define how they are involved in several cellular functions. A potential solution came from basic biochemical experiments in the late 1970s, showing that some mushroom extracts exert hemolytic activities. These activities were later assigned to aegerolysin-based sphingomyelin/cholesterol-specific cytolytic protein complexes. Recently, six sphingomyelin/cholesterol binding proteins from different mushrooms have been identified and have provided some insight into the nature of sphingomyelin/cholesterol-rich domains in living vertebrate cells. In this review, we dissect the accumulated knowledge and introduce the mushroom lipid raft binding proteins as molecules of choice to study the dynamics and origins of these liquid-ordered domains in mammalian cells.

scholarly journals Modeling the effects of cyclodextrin on intracellular membrane vesicles from Cos-7 cells prepared by sonication and carbonate treatment

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1351 ◽  
Author(s):  
Peter Kilbride ◽  
Holly J. Woodward ◽  
Kuan Boone Tan ◽  
Nguyễn T.K. Thanh ◽  
K.M. Emily Chu ◽  
...  
Keyword(s):  
Lipid Rafts ◽  
Cell Biology ◽  
Buoyant Density ◽  
Membrane Vesicles ◽  
Membrane Microdomains ◽  
Intracellular Membrane ◽  
Liquid Ordered ◽  
Mathematical Analyses ◽  
Phosphatidylinositol 4 ◽  
Induced Changes

Cholesterol has important functions in the organization of membrane structure and this may be mediated via the formation of cholesterol-rich, liquid-ordered membrane microdomains often referred to as lipid rafts. Methyl-beta-cyclodextrin (cyclodextrin) is commonly used in cell biology studies to extract cholesterol and therefore disrupt lipid rafts. However, in this study we reassessed this experimental strategy and investigated the effects of cyclodextrin on the physical properties of sonicated and carbonate-treated intracellular membrane vesicles isolated from Cos-7 fibroblasts. We treated these membranes, which mainly originate from thetrans-Golgi network and endosomes, with cyclodextrin and measured the effects on their equilibrium buoyant density, protein content, represented by the palmitoylated protein phosphatidylinositol 4-kinase type IIα, and cholesterol. Despite the reduction in mass stemming from cholesterol removal, the vesicles became denser, indicating a possible large volumetric decrease, and this was confirmed by measurements of hydrodynamic vesicle size. Subsequent mathematical analyses demonstrated that only half of this change in membrane size was attributable to cholesterol loss. Hence, the non-selective desorption properties of cyclodextrin are also involved in membrane size and density changes. These findings may have implications for preceding studies that interpreted cyclodextrin-induced changes to membrane biochemistry in the context of lipid raft disruption without taking into account our finding that cyclodextrin treatment also reduces membrane size.

Free fatty acid transport across adipocytes is mediated by an unknown membrane protein pump

2007 ◽  
Vol 293 (5) ◽  
pp. E1207-E1214 ◽  
Author(s):  
J. Patrick Kampf ◽  
Danielle Parmley ◽  
Alan M. Kleinfeld
Keyword(s):  
Fatty Acid ◽  
Membrane Protein ◽  
Lipid Rafts ◽  
Cell Lines ◽  
Fatty Acid Transport ◽  
Acid Transport ◽  
Long Chain Fatty Acid ◽  
Caveolin 1 ◽  
Long Chain

The role of cell membranes in regulating the flux of long chain free fatty acids (FFA) into and out of adipocytes is intensely debated. Four different membrane proteins including, FABPpm, CD36/FAT, caveolin-1, and FATP have been identified as facilitating FFA transport. Moreover, CD36 and caveolin-1 are also reported to mediate transport in conjunction with lipid rafts. The principal evidence for these findings is a correlation of the level of FFA uptake with the expression level of these proteins and with the integrity of lipid rafts. The 3T3-L1 and 3T3-F442A cell lines in their preadipocyte states reveal little or no expression of these proteins and correspondingly low levels of uptake. Here we have microinjected the adipocyte and preadipocyte cell lines with ADIFAB, the fluorescent indicator of FFA. The ADIFAB fluorescence allowed us to monitor the intracellular unbound FFA concentration during FFA influx and efflux. We show that these measurements of transport, in contrast to FFA uptake measurements, correlate neither with expression of these proteins nor with lipid raft integrity in preadipocytes and adipocytes. Transport characteristics, including the generation of an ATP-dependent FFA concentration gradient, are virtually identical in adipocytes and preadipocytes. We suggest that the origin of the discrepancy between uptake and our measurements is that most of the FFA transported into the cells is lost during the uptake but not in the transport protocols. We conclude that long chain fatty acid transport in adipocytes is very likely mediated by an as-yet-unidentified membrane protein pump.

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