Hemagglutinin of Influenza Virus Partitions into the Nonraft Domain of Model Membranes

Nikolaus, Jörg; Scolari, Silvia; Bayraktarov, Elisa; Jungnick, Nadine; Engel, Stephanie; Plazzo, Anna Pia; Stöckl, Martin; Volkmer, Rudolf; Veit, Michael; Herrmann, Andreas

doi:10.1016/j.bpj.2010.04.027

Cited by 58 publications

(68 citation statements)

References 66 publications

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“…These findings disprove the hypothesis that hemagglutinin clustering is caused by an attraction to ordered plasma membrane domains that are enriched with cholesterol and sphingolipids. This conclusion is consistent with biophysical studies that indicated hemagglutinin is not located within cholesterol-rich liquid-ordered membrane domains (Hess et al, 2005, 2007; Polozov et al, 2008; Nikolaus et al, 2010). …”

Section: Direct Imaging Of Sphingolipid Distribution In the Plasma Mesupporting

confidence: 89%

Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It

Kraft

2017

Front. Cell Dev. Biol.

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Sphingolipids are structural components in the plasma membranes of eukaryotic cells. Their metabolism produces bioactive signaling molecules that modulate fundamental cellular processes. The segregation of sphingolipids into distinct membrane domains is likely essential for cellular function. This review presents the early studies of sphingolipid distribution in the plasma membranes of mammalian cells that shaped the most popular current model of plasma membrane organization. The results of traditional imaging studies of sphingolipid distribution in stimulated and resting cells are described. These data are compared with recent results obtained with advanced imaging techniques, including super-resolution fluorescence detection and high-resolution secondary ion mass spectrometry (SIMS). Emphasis is placed on the new insight into the sphingolipid organization within the plasma membrane that has resulted from the direct imaging of stable isotope-labeled lipids in actual cell membranes with high-resolution SIMS. Super-resolution fluorescence techniques have recently revealed the biophysical behaviors of sphingolipids and the unhindered diffusion of cholesterol analogs in the membranes of living cells are ultimately in contrast to the prevailing hypothetical model of plasma membrane organization. High-resolution SIMS studies also conflicted with the prevailing hypothesis, showing sphingolipids are concentrated in micrometer-scale membrane domains, but cholesterol is evenly distributed within the plasma membrane. Reductions in cellular cholesterol decreased the number of sphingolipid domains in the plasma membrane, whereas disruption of the cytoskeleton eliminated them. In addition, hemagglutinin, a transmembrane protein that is thought to be a putative raft marker, did not cluster within sphingolipid-enriched regions in the plasma membrane. Thus, sphingolipid distribution in the plasma membrane is dependent on the cytoskeleton, but not on favorable interactions with cholesterol or hemagglutinin. The alternate views of plasma membrane organization suggested by these findings are discussed.

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Section: Direct Imaging Of Sphingolipid Distribution In the Plasma Mesupporting

confidence: 89%

Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It

Kraft

2017

Front. Cell Dev. Biol.

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“…In living cells, the differences between Lo and Ld domains are less pronounced than they can be in model membranes, due to the more complex lipid composition and high protein concentration in the plasma membrane, which may hamper the tight lipid packing in Lo (49,50). In particular, in the model membrane used in our simulations, the almost complete depletion of unsaturated lipids from Lo yields a very ordered domain.…”

Section: Discussionmentioning

confidence: 90%

“…The incorporation of this peptide is facilitated by the transient formation of an island of unsaturated lipids pervading the ordered domain, emphasizing that it is the collective motion of both lipids and peptides that plays a role in the lateral sorting process. Thus far, no TM peptides or proteins that partition into Lo domains in model membranes were reported (33,(45)(46)(47)(48)(49), irrespective of the amino acid sequence. However, the underlying molecular mechanisms and thermodynamic driving forces were poorly understood.…”

Section: Discussionmentioning

confidence: 99%

Lipid packing drives the segregation of transmembrane helices into disordered lipid domains in model membranes

Schäfer

Jong

Holt

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

227

265

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Cell membranes are comprised of multicomponent lipid and protein mixtures that exhibit a complex partitioning behavior. Regions of structural and compositional heterogeneity play a major role in the sorting and self-assembly of proteins, and their clustering into higher-order oligomers. Here, we use computer simulations and optical microscopy to study the sorting of transmembrane helices into the liquid-disordered domains of phase-separated model membranes, irrespective of peptide-lipid hydrophobic mismatch. Free energy calculations show that the enthalpic contribution due to the packing of the lipids drives the lateral sorting of the helices. Hydrophobic mismatch regulates the clustering into either small dynamic or large static aggregates. These results reveal important molecular driving forces for the lateral organization and self-assembly of transmembrane helices in heterogeneous model membranes, with implications for the formation of functional protein complexes in real cells.fluorescence microscopy | lipid rafts | membrane proteins | molecular dynamics | linactants T he heterogeneity of biological membranes plays an important role in cellular function (1, 2). Despite experimental progress in recent years (3), the characterization of lateral organization in biological membranes, however, remains challenging due to the lack of tools to study fluctuating nanoscale assemblies in living cells (4-6). Model membranes (7-10) as well as isolated plasma membranes (11, 12) are more frequently studied, because largescale phase separation can be observed in these systems. In particular, at cholesterol concentrations reminiscent of biological membranes (10-30 mol % cholesterol), ternary mixtures of saturated and unsaturated lipids can segregate into coexisting lipid domains of different fluidity, a liquid-ordered (Lo) and a liquiddisordered (Ld) phase. Probing the structural and dynamical properties of these fluid domains has received a lot of attention, as it is presumably linked to the formation of lipid nanodomains ("rafts") in real cells (13,14).The structure and function of membrane proteins is intimately connected with their lipid environment (15, 16). Because of the heterogeneity of the cell membrane, proteins partition between different lipid domains, are recruited to specific locations, and form functional complexes (17)(18)(19). This lateral organization is very important for various cellular processes, such as membrane fusion (20, 21), protein trafficking (22), and signal transduction (23-25). Although lipids and integral membrane proteins are well studied by themselves, the molecular properties that determine the specific interactions between them remain poorly understood. Interactions important for protein sorting and self-assembly are (specific) protein-protein and protein-lipid forces, and indirect lipid-mediated forces. The latter category includes, for instance, forces due to entropic confinement of lipid chains and forces arising from the mismatch between the hydrophobic parts of the protein and the bi...

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“…However, several predicted raft proteins [e.g., LAT (14) and influenza hemagglutinin (13,29)] failed to enrich in the ordered phase in vesicles prepared using the standard PFA/ DTT preparation. Raft phase enrichment of LAT in nGPMVs resolves this discrepancy and suggests that the mechanism behind nonraft partitioning of raft TM proteins in pdGPMVs is depalmitoylation by the reducing agent present in this preparation.…”

Section: Discussionmentioning

confidence: 99%

Palmitoylation regulates raft affinity for the majority of integral raft proteins

Levental

Lingwood

Grzybek

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

500

487

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The physical basis for protein partitioning into lipid rafts remains an outstanding question in membrane biology that has previously been addressed only through indirect techniques involving differential solubilization by nonionic detergents. We have used giant plasma membrane vesicles, a plasma membrane model system that phase separates to include an ordered phase enriching for raft constituents, to measure the partitioning of the transmembrane linker for activation of Tcells (LAT). LATenrichment in the raft phase was dependent on palmitoylation at two juxtamembrane cysteines and could be enhanced by oligomerization. This palmitoylation requirement was also shown to regulate raft phase association for the majority of integral raft proteins. Because cysteine palmitoylation is the only lipid modification that has been shown to be reversibly regulated, our data suggest a role for palmitoylation as a dynamic raft targeting mechanism for transmembrane proteins.phase separation | raft partitioning | posttranslational modification | GPI-anchored protein P osttranslational modifications allow for rapid modulation of protein structure, localization, and function. An important class is lipid modifications, which includes the addition of GPI anchors, sterols, as well as single saturated and/or unsaturated fatty acids. The cellular purpose of protein lipidation is often to anchor the modified polypeptide to membranes; however, the functional significance of the widespread S acylation of transmembrane (TM) proteins remains unclear. Additionally, S acylation, often referred to as "palmitoylation" due to the addition of a cysteine-linked palmitate, is the only protein lipidation under dynamic enzymatic regulation, implying a potentially important regulatory role (1).Adapting a recently developed experimental system for measuring protein partitioning between coexisting fluid domains in cell-derived isolated plasma membranes, we find that palmitoylation regulates raft phase affinity of LAT (linker for activation of T cells), a critical adaptor in immune system signaling. This finding extends to the majority of raft phase partitioning proteins, suggesting a general role for protein palmitoylation in dynamic regulation of raft association. Although previous studies (2-7) have implicated palmitoylation in regulation of detergent resistance of TM proteins, the indirect and controversial nature of these experiments has limited their applicability in assigning raft affinity. The results presented here directly demonstrate and quantify the vital role of palmitoylation in partitioning of TM proteins to raft phase domains of isolated plasma membranes (PM). ResultsLAT Partitioning Is Disrupted by DTT. Giant plasma membrane vesicles (GPMVs) are cell-and cytoskeleton-detached, organellefree PM blebs that maintain the protein (8) and lipid (9) diversity of the native membrane and separate into two liquid phases (10) with different order (11) mirroring the behavior of pure lipid liposomes (12). Remarkably, phase separation sorts membrane com...

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Hemagglutinin of Influenza Virus Partitions into the Nonraft Domain of Model Membranes

Cited by 58 publications

References 66 publications

Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It

Sphingolipid Organization in the Plasma Membrane and the Mechanisms That Influence It

Lipid packing drives the segregation of transmembrane helices into disordered lipid domains in model membranes

Palmitoylation regulates raft affinity for the majority of integral raft proteins

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