The involvement of lipid rafts in the regulation of integrin function

2002 ◽  
Vol 115 (5) ◽  
pp. 963-972 ◽  
Author(s):  
Birgit Leitinger ◽  
Nancy Hogg
Keyword(s):  
T Lymphocytes ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Integrin Activation ◽  
Functional Relevance ◽  
Intact Lipid

Integrin activity on cells such as T lymphocytes is tightly controlled. Here we demonstrate a key role for lipid rafts in regulating integrin function. Without stimulation integrin LFA-1 is excluded from lipid rafts, but following activation LFA-1 is mobilised to the lipid raft compartment. An LFA-1 construct from which the I domain has been deleted mimics activated integrin and is constitutively found in lipid rafts. This correlation between integrin activation and raft localisation extends to a second integrin,α4β1, and the clustering of α4β1 is also raft dependent. Both LFA-1 and α4β1-mediated adhesion is dependent upon intact lipid rafts providing proof of the functional relevance of the lipid raft localisation. Finally we find that non-raft integrins are excluded from the rafts by cytoskeletal constraints. The presence of integrin in lipid rafts under stimulating conditions that activate these receptors strongly indicates that the rafts have a key role in positively regulating integrin activity.

scholarly journals CD44 Engagement Promotes Matrix-Derived Survival through the CD44-SRC-Integrin Axis in Lipid Rafts

2008 ◽  
Vol 28 (18) ◽  
pp. 5710-5723 ◽  
Author(s):  
Jia-Lin Lee ◽  
Mei-Jung Wang ◽  
Putty-Reddy Sudhir ◽  
Jeou-Yuan Chen
Keyword(s):  
Lipid Rafts ◽  
Lipid Raft ◽  
Integrin Activation ◽  
Variant Isoforms ◽  
Survival Signal ◽  
The Matrix ◽  
Signaling Axis ◽  
Tightly Coupled ◽  
Carboxyl Terminal

ABSTRACT CD44 is present in detergent-resistant, cholesterol-rich microdomains, called lipid rafts, in many types of cells. However, the functional significance of CD44 in lipid rafts is still unknown. We have previously demonstrated that osteopontin-mediated engagement of CD44 spliced variant isoforms promotes an extracellular matrix-derived survival signal through integrin activation. By using a series of CD44 mutants and pharmacological inhibitors selectively targeted to various cellular pathways, we show in this study that engagement of CD44 induces lipid raft coalescence to facilitate a CD44-Src-integrin signaling axis in lipid rafts, leading to increased matrix-derived survival. Palmitoylation of the membrane-proximal cysteine residues and carboxyl-terminal linkage to the actin cytoskeleton both contribute to raft targeting of CD44. The enrichment of integrin β1 in lipid rafts is tightly coupled to CD44 ligation-elicited lipid raft reorganization and associated with temporally delayed endocytosis. Through the interaction with the CD44 carboxyl-terminal ankyrin domain, Src is cotranslocated to lipid rafts, where it induces integrin activation via an inside-out mechanism. Collectively, this study demonstrates an important role of the dynamic raft reorganization induced by CD44 clustering in eliciting the matrix-derived survival signal.

scholarly journals Nef Associates with p21-Activated Kinase 2 in a p21-GTPase-Dependent Dynamic Activation Complex within Lipid Rafts

2004 ◽  
Vol 78 (23) ◽  
pp. 12773-12780 ◽  
Author(s):  
Kati Pulkkinen ◽  
G. Herma Renkema ◽  
Frank Kirchhoff ◽  
Kalle Saksela
Keyword(s):  
Catalytic Activity ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Kinase Activity ◽  
Highly Active ◽  
Membrane Compartment ◽  
Per Se ◽  
P21 Activated Kinase ◽  
Autoregulatory Mechanism ◽  
Pak2 Activation

ABSTRACT We have previously reported that Nef specifically interacts with a small but highly active subpopulation of p21-activated kinase 2 (PAK2). Here we show that this is due to a transient association of Nef with a PAK2 activation complex within a detergent-insoluble membrane compartment containing the lipid raft marker GM1. The low abundance of this Nef-associated kinase (NAK) complex was found to be due to an autoregulatory mechanism. Although activation of PAK2 was required for assembly of the NAK complex, catalytic activity of PAK2 also promoted dissociation of this complex. Testing different constitutively active PAK2 mutants indicated that the conformation associated with p21-mediated activation rather than kinase activity per se was required for PAK2 to become NAK. Although association with PAK2 is one of the most conserved properties of Nef, we found that the ability to stimulate PAK2 activity differed markedly among divergent Nef alleles, suggesting that PAK2 association and activation are distinct functions of Nef. However, mutations introduced into the p21-binding domain of PAK2 revealed that p21-GTPases are involved in both of these Nef functions and, in addition to promoting PAK2 activation, also help to physically stabilize the NAK complex.

scholarly journals Lipid raft–dependent plasma membrane repair interferes with the activation of B lymphocytes

2015 ◽  
Vol 211 (6) ◽  
pp. 1193-1205 ◽  
Author(s):  
Heather Miller ◽  
Thiago Castro-Gomes ◽  
Matthias Corrotte ◽  
Christina Tam ◽  
Timothy K. Maugel ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
B Cell ◽  
B Lymphocytes ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Cell Activation ◽  
Dependent Manner ◽  
B Cell Activation ◽  
Membrane Repair ◽  
Membrane Injury

Cells rapidly repair plasma membrane (PM) damage by a process requiring Ca2+-dependent lysosome exocytosis. Acid sphingomyelinase (ASM) released from lysosomes induces endocytosis of injured membrane through caveolae, membrane invaginations from lipid rafts. How B lymphocytes, lacking any known form of caveolin, repair membrane injury is unknown. Here we show that B lymphocytes repair PM wounds in a Ca2+-dependent manner. Wounding induces lysosome exocytosis and endocytosis of dextran and the raft-binding cholera toxin subunit B (CTB). Resealing is reduced by ASM inhibitors and ASM deficiency and enhanced or restored by extracellular exposure to sphingomyelinase. B cell activation via B cell receptors (BCRs), a process requiring lipid rafts, interferes with PM repair. Conversely, wounding inhibits BCR signaling and internalization by disrupting BCR–lipid raft coclustering and by inducing the endocytosis of raft-bound CTB separately from BCR into tubular invaginations. Thus, PM repair and B cell activation interfere with one another because of competition for lipid rafts, revealing how frequent membrane injury and repair can impair B lymphocyte–mediated immune responses.

Mediators of innate immune recognition of bacteria concentrate in lipid rafts and facilitate lipopolysaccharide-induced cell activation

2002 ◽  
Vol 115 (12) ◽  
pp. 2603-2611 ◽  
Author(s):  
Martha Triantafilou ◽  
Kensuke Miyake ◽  
Douglas T. Golenbock ◽  
Kathy Triantafilou
Keyword(s):  
Lipid Rafts ◽  
Lipid Raft ◽  
Cell Activation ◽  
Imaging Techniques ◽  
Recognition System ◽  
Innate Immune ◽  
Membrane Microdomains ◽  
Immune Recognition ◽  
Cellular Activation ◽  
Signalling Molecules

The plasma membrane of cells is composed of lateral heterogeneities,patches and microdomains. These membrane microdomains or lipid rafts are enriched in glycosphingolipids and cholesterol and have been implicated in cellular processes such as membrane sorting and signal transduction. In this study we investigated the importance of lipid raft formation in the innate immune recognition of bacteria using biochemical and fluorescence imaging techniques. We found that receptor molecules that are implicated in lipopolysaccharide (LPS)-cellular activation, such as CD14, heat shock protein(hsp) 70, 90, Chemokine receptor 4 (CXCR4), growth differentiation factor 5(GDF5) and Toll-like receptor 4 (TLR4), are present in microdomains following LPS stimulation. Lipid raft integrity is essential for LPS-cellular activation, since raft-disrupting drugs, such as nystatin or MCD, inhibit LPS-induced TNF-α secretion. Our results suggest that the entire bacterial recognition system is based around the ligation of CD14 by bacterial components and the recruitment of multiple signalling molecules, such as hsp70, hsp90, CXCR4, GDF5 and TLR4, at the site of CD14-LPS ligation, within the lipid rafts.

scholarly journals Lipid rafts mediate internalization of β1-integrin in migrating intestinal epithelial cells

2008 ◽  
Vol 295 (5) ◽  
pp. G965-G976 ◽  
Author(s):  
Elena V. Vassilieva ◽  
Kirsten Gerner-Smidt ◽  
Andrei I. Ivanov ◽  
Asma Nusrat
Keyword(s):  
Epithelial Cells ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Intestinal Epithelial Cells ◽  
Focal Adhesions ◽  
Endocytic Pathway ◽  
Dependent Manner ◽  
Intestinal Epithelial ◽  
Caveolin 1 ◽  
Cell Matrix

Intestinal mucosal inflammation is associated with epithelial wounds that rapidly reseal by migration of intestinal epithelial cells (IECs). Cell migration involves cycles of cell-matrix adhesion/deadhesion that is mediated by dynamic turnover (assembly and disassembly) of integrin-based focal adhesions. Integrin endocytosis appears to be critical for deadhesion of motile cells. However, mechanisms of integrin internalization during remodeling of focal adhesions of migrating IECs are not understood. This study was designed to define the endocytic pathway that mediates internalization of β1-integrin in migrating model IECs. We observed that, in SK-CO15 and T84 colonic epithelial cells, β1-integrin is internalized in a dynamin-dependent manner. Pharmacological inhibition of clathrin-mediated endocytosis or macropinocytosis and small-interfering RNA (siRNA)-mediated knock down of clathrin did not prevent β1-integrin internalization. However, β1-integrin internalization was inhibited following cholesterol extraction and after overexpression of lipid raft protein, caveolin-1. Furthermore, internalized β1-integrin colocalized with the lipid rafts marker cholera toxin, and siRNA-mediated knockdown of caveolin-1 and flotillin-1/2 increased β1-integrin endocytosis. Our data suggest that, in migrating IEC, β1-integrin is internalized via a dynamin-dependent lipid raft-mediated pathway. Such endocytosis is likely to be important for disassembly of integrin-based cell-matrix adhesions and therefore in regulating IEC migration and wound closure.

scholarly journals Palmitoylation of the Autographa californica Multicapsid Nucleopolyhedrovirus Envelope Glycoprotein GP64: Mapping, Functional Studies, and Lipid Rafts

2003 ◽  
Vol 77 (11) ◽  
pp. 6265-6273 ◽  
Author(s):  
Sandy Xiaoxin Zhang ◽  
Yu Han ◽  
Gary W. Blissard
Keyword(s):  
Cell Surface ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Envelope Glycoprotein ◽  
Cysteine Residue ◽  
Autographa Californica ◽  
Membrane Microdomains ◽  
Sf9 Cells ◽  
Wild Type ◽  
Lipid Raft Microdomains

ABSTRACT Budded virions (BV) of the baculovirus Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) contain a major envelope glycoprotein known as GP64, which was previously shown to be palmitoylated. In the present study, we used truncation and amino acid substitution mutations to map the palmitoylation site to cysteine residue 503. Palmitoylation of GP64 was not detected when Cys503 was replaced with alanine or serine. Palmitoylation-minus forms of GP64 were used to replace wild-type GP64 in AcMNPV, and these viruses were used to examine potential functions of GP64 palmitoylation in the context of the infection cycle. Analysis by immunoprecipitation and cell surface studies revealed that palmitoylation of GP64 did not affect GP64 synthesis or its transport to the cell surface in Sf9 cells. GP64 proteins lacking palmitoylation also mediated low-pH-triggered membrane fusion in a manner indistinguishable from that of wild-type GP64. Cells infected with viruses expressing palmitoylation-minus forms of GP64 produced infectious virions at levels similar to those from cells infected with wild-type AcMNPV. In combination, these data suggest that virus entry and exit in Sf9 cells were not significantly affected by GP64 palmitoylation. To determine whether GP64 palmitoylation affected the association of GP64 with membrane microdomains, the potential association of GP64 with lipid raft microdomains was examined. These experiments showed that: (i) AcMNPV-infected Sf9 cell membranes contain lipid raft microdomains, (ii) GP64 association with lipid rafts was not detected in infected Sf9 cells, and (iii) GP64 palmitoylation did not affect the apparent exclusion of GP64 from lipid raft microdomains.

scholarly journals Interaction of drugs with lipid raft membrane domains as a possible target

2020 ◽  
Vol 14 (1) ◽  
pp. 34-47
Author(s):  
Hironori Tsuchiya ◽  
Maki Mizogami
Keyword(s):  
Membrane Fluidity ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Plasma Membranes ◽  
Cellular Membrane ◽  
Membrane Lipid ◽  
Membrane Domains ◽  
Functional Protein ◽  
Lipid Complex ◽  
Physicochemical Changes

Introduction: Plasma membranes are not the homogeneous bilayers of uniformly distributed lipids but the lipid complex with laterally separated lipid raft membrane domains, which provide receptor, ion channel and enzyme proteins with a platform. The aim of this article is to review the mechanistic interaction of drugs with membrane lipid rafts and address the question whether drugs induce physicochemical changes in raft-constituting and raft-surrounding membranes. Methods: Literature searches of PubMed/MEDLINE and Google Scholar databases from 2000 to 2020 were conducted to include articles published in English in internationally recognized journals. Collected articles were independently reviewed by title, abstract and text for relevance. Results: The literature search indicated that pharmacologically diverse drugs interact with raft model membranes and cellular membrane lipid rafts. They could physicochemically modify functional protein-localizing membrane lipid rafts and the membranes surrounding such domains, affecting the raft organizational integrity with the resultant exhibition of pharmacological activity. Raft-acting drugs were characterized as ones to decrease membrane fluidity, induce liquid-ordered phase or order plasma membranes, leading to lipid raft formation; and ones to increase membrane fluidity, induce liquid-disordered phase or reduce phase transition temperature, leading to lipid raft disruption. Conclusion: Targeting lipid raft membrane domains would open a new way for drug design and development. Since angiotensin-converting enzyme 2 receptors which are a cell-specific target of and responsible for the cellular entry of novel coronavirus are localized in lipid rafts, agents that specifically disrupt the relevant rafts may be a drug against coronavirus disease 2019.

scholarly journals Copatching and Lipid Raft Association of Different Viral Glycoproteins Expressed on the Surfaces of Pseudorabies Virus-Infected Cells

2004 ◽  
Vol 78 (10) ◽  
pp. 5279-5287 ◽  
Author(s):  
Herman W. Favoreel ◽  
Thomas C. Mettenleiter ◽  
Hans J. Nauwynck
Keyword(s):  
Lipid Rafts ◽  
Lipid Raft ◽  
Plasma Membranes ◽  
Pseudorabies Virus ◽  
Viral Proteins ◽  
Viral Envelope ◽  
Viral Glycoprotein ◽  
Monospecific Antibody ◽  
Infected Cells ◽  
Simplex Virus

ABSTRACT Pseudorabies virus (PRV) is a swine alphaherpesvirus that is closely related to human herpes simplex virus (HSV). Both PRV and HSV express a variety of viral envelope glycoproteins in the plasma membranes of infected cells. Here we show that at least four major PRV glycoproteins (gB, gC, gD, and gE) in the plasma membrane of infected swine kidney cells and monocytes seem to be linked, since monospecific antibody-induced patching of any one of these proteins results in copatching of the others. Further, for all four PRV glycoproteins, monospecific antibody-induced patches were enriched in GM1, a typical marker of lipid raft microdomains, but were excluded for transferrin receptor, a nonraft marker, suggesting that these viral proteins may associate with lipid rafts. However, only gB and, to a lesser extent, gE were found in lipid raft fractions by using detergent floatation assays, indicating that gC and gD do not show strong lipid raft association. Addition of methyl-β-cyclodextrin (MCD), a cholesterol-depleting agent that is commonly used to disrupt lipid rafts, only slightly reduced copatching efficiency between the different viral proteins, indicating that other factors, perhaps tegument-glycoprotein interactions, may be important for the observed copatching events. On the other hand, MCD strongly reduced polarization of the antibody-induced viral glycoprotein patches to a cap structure, a gE-dependent process that has been described for specific PRV- and HSV-infected cells. Therefore, we hypothesize that efficient gE-mediated capping of antibody-antigen patches may require the lipid raft-associated signal transduction machinery.

scholarly journals Distinct Roles of Cellular Lck and p80 Proteins in Herpesvirus Saimiri Tip Function on Lipid Rafts

2003 ◽  
Vol 77 (16) ◽  
pp. 9041-9051 ◽  
Author(s):  
Junsoo Park ◽  
Nam-Hyuk Cho ◽  
Joong-Kook Choi ◽  
Pinghui Feng ◽  
Joonho Choe ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Lipid Rafts ◽  
T Cell Receptor ◽  
Protein Interaction ◽  
Lipid Raft ◽  
Cell Receptor ◽  
Herpesvirus Saimiri ◽  
Antigenic Peptides ◽  
Potential Mechanism ◽  
Tumor Virus

ABSTRACT Lipid rafts are proposed to function as platforms for both receptor signaling and trafficking. Following interaction with antigenic peptides, the T-cell receptor (TCR) rapidly translocates to lipid rafts, where it transmits signals and subsequently undergoes endocytosis. The Tip protein of herpesvirus saimiri (HVS), which is a T-lymphotropic tumor virus, interacts with cellular Lck tyrosine kinase and p80, a WD domain-containing endosomal protein. Interaction of Tip with p80 induces enlarged vesicles and recruits Lck and TCR complex into these vesicles for trafficking. We report here that Tip is constitutively present in lipid rafts and that Tip interaction with p80 but not with Lck is necessary for its efficient localization in lipid rafts. The Tip-Lck interaction was required for recruitment of the TCR complex to lipid rafts, and the Tip-p80 interaction was critical for the aggregation and internalization of lipid rafts. These results suggest the potential mechanism for Tip-mediated TCR downregulation: Tip interacts with Lck to recruit TCR complex to lipid rafts, and it subsequently interacts with p80 to initiate the aggregation and internalization of the lipid raft domain and thereby downregulate the TCR complex. Thus, the signaling and targeting functions of HVS Tip rely on two functionally and genetically separable mechanisms that independently target cellular Lck tyrosine kinase and p80 endosomal protein.

Lipid raft adhesion receptors and Syk regulate selectin-dependent rolling under flow conditions

Blood ◽  
2006 ◽  
Vol 108 (10) ◽  
pp. 3352-3359 ◽  
Author(s):  
Claire Abbal ◽  
Martine Lambelet ◽  
Debora Bertaggia ◽  
Carole Gerbex ◽  
Manuel Martinez ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Lipid Rafts ◽  
Lipid Raft ◽  
Chelating Agents ◽  
Regulatory Mechanisms ◽  
Membrane Microdomains ◽  
Leukocyte Rolling ◽  
Flow Conditions ◽  
Cell Rolling ◽  
Pharmacologic Inhibitors

Abstract Selectins and their ligand P-selectin glycoprotein ligand-1 (PSGL-1) mediate leukocyte rolling along inflamed vessels. Cell rolling is modulated by selectin interactions with their ligands and by topographic requirements including L-selectin and PSGL-1 clustering on tips of leukocyte microvilli. Lipid rafts are cell membrane microdomains reported to function as signaling platforms. Here, we show that disruption of leukocyte lipid rafts with cholesterol chelating agents depleted raft-associated PSGL-1 and L-selectin and strongly reduced L-, P-, and E-selectin–dependent rolling. Cholesterol repletion reversed inhibition of cell rolling. Importantly, leukocyte rolling on P-selectin induced the recruitment of spleen tyrosine kinase (Syk), a tyrosine kinase associated to lipid raft PSGL-1. Furthermore, inhibition of Syk activity or expression, with pharmacologic inhibitors or by RNA interference, strongly reduced leukocyte rolling on P-selectin, but not on E-selectin or PSGL-1. These observations identify novel regulatory mechanisms of leukocyte rolling on selectins with a strong dependency on lipid raft integrity and Syk activity.

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