Condensation of the plasma membrane at the site of T lymphocyte activation

Gaus, Katharina; Chklovskaia, Elena; Groth, Barbara Fazekas de St; Jessup, Wendy; Harder, Thomas

doi:10.1083/jcb.200505047

Cited by 233 publications

(250 citation statements)

References 55 publications

Supporting

Mentioning

234

Contrasting

Order By: Relevance

“…The role of lipid rafts in T cell signalling is repeatedly being challenged [23, 35--37] although there is substantial evidence for their involvement in this process [16,19,38,39]. In several studies it was concluded that lipid rafts are involved in T cell signalling because acute cholesterol depletion abolished T cell signalling [10,11,40].…”

Section: Discussionmentioning

confidence: 99%

“…That the T cell plasma membrane of fixed cells that are in contact with beads coated with anti--CD3 antibody is more ordered than the rest of the T cells plasma membrane, has been demonstrated by studying laurdan generalised polarisation [16,17]. In a very recent study by the same group, it was demonstrated that lipids expected to form lipid rafts like cholesterol, sphingomyelin and PC with saturated acyl chains accumulate where T cells interact with beads covered in antibodies against the T cell receptor [21].…”

Section: Discussionmentioning

confidence: 99%

“…If this holds for cell plasma membranes, cholesterol depletion could lead to the aggregation of lipid rafts. That cholesterol and the capability to form raft--like liquid ordered domains are important for membrane condensation (the existence of ordered domains), at the contact site between T cells and beads coated with T cell antigen receptor (TCR) stimulating antibodies, has been demonstrated in fixed cells [16,17].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Limited cholesterol depletion causes aggregation of plasma membrane lipid rafts inducing T cell activation

Mahammad

Dinić

Adler

et al. 2010

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biolog

View full text Add to dashboard Cite

Acute cholesterol depletion is generally associated with decreased or abolished T cell signalling but it can also cause T cell activation. This anomaly has been addressed in Jurkat T cells using progressive cholesterol depletion with methyl--beta--cyclodextrin (MBCD). At depletion levels higher than 50% there is substantial cell death, which explains reports of signalling inhibition. At 10--20% depletion levels, tyrosine phosphorylation is increased, ERK is activated and there is a small increase in cytoplasmic Ca 2+ . Peripheral actin polymerisation is also triggered by limited cholesterol depletion. Strikingly, the lipid raft marker GM1 aggregates upon cholesterol depletion and these aggregated domains concentrate the signalling proteins Lck and LAT, whereas the opposite is true for the non lipid raft marker the transferrin receptor. Using PP2, an inhibitor of Src family kinase activation, it is demonstrated that the lipid raft aggregation occurs independently of and thus upstream of the signalling response. Upon cholesterol depletion there is an increase in overall plasma membrane order, indicative of more liquid ordered domains forming at the expense of liquid disordered domains. That cholesterol depletion and not unspecific effects of MBCD was behind the reported results was confirmed by performing all experiments with MBCD--cholesterol, when no net cholesterol extraction took place. We conclude that non--lethal cholesterol depletion causes the aggregation of lipid rafts which then induces T cell signalling.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Limited cholesterol depletion causes aggregation of plasma membrane lipid rafts inducing T cell activation

Mahammad

Dinić

Adler

et al. 2010

Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biolog

View full text Add to dashboard Cite

show abstract

“…Similarly, Larson et al 41 showed that full length Lyn co-localizes (actually codiffuses as this is an FCS analysis) with crosslinked immunoglobulin E (IgE) receptor, but again the minimal lipid anchor of Lyn coupled to GFP does not. In parallel, Gaus et al 42 have shown, using Laurdan imaging, that the lipids in and around the TCR-protein complex are ordered, which shows with some certainty that these signalling platforms are indeed large, stable L o domains. Together, these observations raise an important question: why do a subset of lipid-modified GFP probes that putatively associate with L o domains (raft markers) not associate with the large putative L o domains that constitute the TCR and IgE receptor signalling platforms?…”

Section: Determinants Of Raft Stabilitymentioning

confidence: 96%

Lipid rafts: contentious only from simplistic standpoints

Hancock

2006

Nat Rev Mol Cell Biol

742

714

View full text Add to dashboard Cite

The hypothesis that lipid rafts exist in plasma membranes and have crucial biological functions remains controversial. The lateral heterogeneity of proteins in the plasma membrane is undisputed, but the contribution of cholesterol-dependent lipid assemblies to this complex, non-random organization promotes vigorous debate. In the light of recent studies with model membranes, computational modelling and innovative cell biology, I propose an updated model of lipid rafts that readily accommodates diverse views on plasma-membrane micro-organization.A widely accepted hypothesis in contemporary cell biology is that freely diffusing, stable, lateral assemblies of sphingolipids and cholesterol, which are termed lipid rafts 1-3 , constitute an important organizing principle for the plasma membrane. The basic concept is that lipid rafts can facilitate selective protein-protein interactions by selectively excluding or including proteins. This lipid-based sorting mechanism has been widely implicated in the assembly of transient signalling platforms and more permanent structures such as the immunological synapse, as well as in the sorting of proteins for entry into specific exocytic and endocytic trafficking pathways [1][2][3] . Despite the undoubted theoretical utility of lipid rafts to many cell biological processes, the basic hypothesis that stable lipid rafts exist at all in biological membranes is under intense scrutiny 4,5 . This is partly because lipid rafts, if they exist in resting cell membranes, are too small to be resolved by fluorescent microscopy and have no defined ultrastructure; therefore, proving their existence is problematic. This article will consider the biophysical properties of model membranes that underpin the lipid raft hypothesis, and the limitations of the biochemical approaches that have been used to study rafts in biological membranes that largely account for the current debate on the hypothesis mentioned above. After examining the challenges that are involved in correlating observations, which have been made in model and cellular membranes, I focus on synthesizing recent data on the size of lipid domains in model membranes with observations that have been obtained by imaging intact plasma membranes. These imaging approaches include single particle tracking (SPT), single fluorophore video tracking (SFVT), fluorescence resonance energy transfer (FRET), homo-FRET and electron microscopy (EM). On the one hand, these studies challenge the simplistic null hypothesis that lipid-based assemblies, such as lipid rafts, do not exist in biological membranes. On the other hand, it is timely to reconsider the raft hypothesis in the light of these new data because the consensus model that emerges is more complex than a simplistic notion of stable, freely diffusing lipid rafts. Some intriguing new questions aboutCompeting interests statement The author declares no competing financial interests. DATABASES

show abstract

“…Gaus and Harder have recently pioneered another approach that relies upon indicator dyes. Using the liquid-order sensing dye Laurdan, they demonstrated that liquid ordered (Lo) lipids are specifically enriched at the IS [11]. In their review, the lessons of this useful dye are discussed and placed into context of the previous studies.…”

mentioning

confidence: 99%

Testing the organization of the immunological synapse

Krummel

2007

Current Opinion in Immunology

View full text Add to dashboard Cite

Upon encounter with antigen-bearing presenting cells, T cells initiate the formation of a unique junction termed the immunological synapse (IS). The morphology of this junction, characterized in EM as a series of discrete contacts into which are interspersed synaptic spaces [1], has multiple similarities to neuronal synapses. The closely apposed membranes permit engagement of T cell receptors (TCR) on T cells with peptide-major histocompatibility complexes (pMHC) as well as distinct contacts for other receptor-ligand pairs such as integrins. The form of this synapse has also been extensively characterized at the level of molecular organization. When TCRs or pMHC complexes are attached to fluorophores, it is found that they first form dynamic and relatively small structures (clusters or 'microclusters') all over the contact area and perhaps predominantly at the outskirts of the synapse [2][3][4]. These ultimately coalesce [3,4] to a central spot and this spot corresponds to a structure first characterized by Kupfer and co-workers in fixed couples and termed the central 'supramolecular activating cluster' or cSMAC [5].The name cSMAC is perhaps misleading since early calcium imaging together with TCR visualization as well as antibody-staining for phosphotyrosine has since shown that activation of signaling actually coincides with the appearance of the smaller clusters, prior to their centralization [3,6]. As the cSMAC is the last spot from which TCRs are likely internalized, it is also the point at which TCR signaling likely ceases [7]. The cSMAC is contrasted by a slightly externalized distribution of CD4 [3] and a larger annulus of integrins such as LFA-1 in the peripheral region (the p-SMAC). The multiple zones of proteins in the IS define distinct membrane domains and the nature of the domains and their function is the overall theme of this issue.The IS involves events that are at once dynamic (involving the cessation of motility, repolarization and coalescence of receptor clusters) as well as having relatively stable aspects. In the last year, Vale and co-workers used a model system in which T cells were triggered by immobilized antibodies to demonstrate that TCRs are confined to relatively stable zones that behave as if they are bounded by a diffusion barrier [8]. This suggests that, while the pathway from an unstimulated cell surface to a highly ordered cSMAC/pSMAC array is highly dynamic, it is also highly aided by stabilizing forces in the membrane or in the cytoskeleton. As it is tested more, it becomes clear that the dynamic assembly of the IS relies upon a confluence of biophysical processes within the membrane, and cell biological processes deriving from other proteins in the membrane or within the cytosol and recent efforts have focused upon all of these. The foremost structure being studied is the lipid bilayer and the proteins arrays that assemble within this unique environment.

show abstract

Condensation of the plasma membrane at the site of T lymphocyte activation

Cited by 233 publications

References 55 publications

Limited cholesterol depletion causes aggregation of plasma membrane lipid rafts inducing T cell activation

Limited cholesterol depletion causes aggregation of plasma membrane lipid rafts inducing T cell activation

Lipid rafts: contentious only from simplistic standpoints

Testing the organization of the immunological synapse

Contact Info

Product

Resources

About