Retroviruses Human Immunodeficiency Virus and Murine Leukemia Virus Are Enriched in Phosphoinositides

104

139

The interaction between HIV and dendritic cells (DCs) is an important early event in HIV-1 pathogenesis that leads to efficient viral dissemination. Here we demonstrate a HIV gp120-independent DC capture mechanism that uses virion-incorporated hostderived gangliosides with terminal α2-3-linked sialic acid linkages. Using exogenously enriched virus and artificial liposome particles, we demonstrate that both α2-3 gangliosides GM1 and GM3 are capable of mediating this interaction when present in the particle at high levels. In the absence of overexpression, GM3 is the primary ligand responsible for this capture mechanism, because siRNA depletion of GM3 but not GM1 from the producer cell and hence virions, resulted in a dramatic decrease in DC capture. Furthermore, HIV-1 capture by DCs was competitively inhibited by targeting virion-associated GM3, but was unchanged by targeting GM1. Finally, virions were derived from monocytoid THP-1 cells that constitutively display low levels of GM1 and GM3, or from THP-1 cells induced to express high surface levels of GM1 and GM3 upon stimulation with the TLR2/1 ligand Pam3CSK4. Compared with untreated THP-1 cells, virus produced from Pam3CSK4-stimulated THP-1 cells incorporated higher levels of GM3, but not GM1, and showed enhanced DC capture and trans-infection. Our results identify a unique HIV-1 DC attachment mechanism that is dependent on a host-cell-derived ligand, GM3, and is a unique example of pathogen mimicry of host-cell recognition pathways that drive virus capture and dissemination in vivo.

Section: Discussionsupporting

confidence: 82%

Section: Enrichment Of α2-3-linked Gangliosides Results In Enhanced Hmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

HIV-1 incorporation of host-cell–derived glycosphingolipid GM3 allows for capture by mature dendritic cells

Puryear

Ramirez

et al. 2012

104

139

“…This high membrane order can be related to two causes. First, as cholesterol concentration is more than 40% in plasma membranes (40,41), not only the ordered but also the disordered phase of GPMVs likely contains considerable amounts of cholesterol, increasing the packing in the membrane. In addition, both phases are above the order of the unseparated GPMVs at 20°C (Fig.…”

Section: Analysis Of Phase Separation In Plasma Membranesmentioning

confidence: 99%

Order of lipid phases in model and plasma membranes

Kaiser

Lingwood

Levental

et al. 2009

425

396

Lipid rafts are nanoscopic assemblies of sphingolipids, cholesterol, and specific membrane proteins that contribute to lateral heterogeneity in eukaryotic membranes. Separation of artificial membranes into liquid-ordered (Lo) and liquid-disordered phases is regarded as a common model for this compartmentalization. However, tight lipid packing in Lo phases seems to conflict with efficient partitioning of raft-associated transmembrane (TM) proteins. To assess membrane order as a component of raft organization, we performed fluorescence spectroscopy and microscopy with the membrane probes Laurdan and C-laurdan. First, we assessed lipid packing in model membranes of various compositions and found cholesterol and acyl chain dependence of membrane order. Then we probed cell membranes by using two novel systems that exhibit inducible phase separation: giant plasma membrane vesicles [Baumgart et al. (2007) Proc Natl Acad Sci USA 104:3165-3170] and plasma membrane spheres. Notably, only the latter support selective inclusion of raft TM proteins with the ganglioside GM1 into one phase. We measured comparable small differences in order between the separated phases of both biomembranes. Lateral packing in the ordered phase of giant plasma membrane vesicles resembled the Lo domain of model membranes, whereas the GM1 phase in plasma membrane spheres exhibited considerably lower order, consistent with different partitioning of lipid and TM protein markers. Thus, lipid-mediated coalescence of the GM1 raft domain seems to be distinct from the formation of a Lo phase, suggesting additional interactions between proteins and lipids to be effective.generalized polarization value ͉ giant unilamellar vesicle ͉ membrane organization ͉ lipid sorting ͉ lipid raft T he lipid raft hypothesis postulates that selective interactions among sphingolipids, cholesterol, and membrane proteins contribute to lateral membrane heterogeneity (1). A tenet of the model is that small, dynamic cholesterol-sphingolipid-enriched assemblies can be induced to coalesce into larger, more stable structures through clustering of domain components (2). Although experimental data support cholesterol-dependent nano-scale membrane heterogeneity (3-8) and selective domain formation upon raft cross-linking (9-12), the mechanisms that govern such associations in cell membranes remain unclear.On the molecular level, a key feature that is thought to contribute to raft assembly is the propensity of cholesterol to pack tightly with saturated acyl chains of lipids causing them to adopt an extended conformation (13,14). In multi-component model membranes (n Ͼ 2), this interaction can lead to microscopically separate fluid membrane phases: the liquid-ordered (Lo) phase, enriched in saturated (sphingo-)lipids and cholesterol in a highly condensed state, and the liquid-disordered (Ld) phase, enriched in unsaturated glycerophospholipid in a disordered state (15)(16)(17).Several features of the Lo phase in model membranes correspond to the predicted properties of lipid rafts in cel...

“…Only binding and rearrangements of virion glycoproteins releases energy to overcome the requirements for the formation of the negative curvature essential for fusion (19)(20)(21)(22). Furthermore, outer leaflets of virion envelopes are commonly enriched in glycolipids with relatively large hydrophilic heads, such as gangliosides, which favor positive curvature (23,24).…”

mentioning

confidence: 99%

Rigid amphipathic fusion inhibitors, small molecule antiviral compounds against enveloped viruses

St.Vincent¹,

Colpitts

Устинов

et al. 2010

141

130

Antiviral drugs targeting viral proteins often result in prompt selection for resistance. Moreover, the number of viral targets is limited. Novel antiviral targets are therefore needed. The unique characteristics of fusion between virion envelopes and cell membranes may provide such targets. Like all fusing bilayers, viral envelopes locally adopt hourglass-shaped stalks during the initial stages of fusion, a process that requires local negative membrane curvature. Unlike cellular vesicles, however, viral envelopes do not redistribute lipids between leaflets, can only use the energy released by virion proteins, and fuse to the extracellular leaflets of cell membranes. Enrichment in phospholipids with hydrophilic heads larger than their hydrophobic tails in the convex outer leaflet of vesicles favors positive curvature, therefore increasing the activation energy barrier for fusion. Such phospholipids can increase the activation barrier beyond the energy provided by virion proteins, thereby inhibiting viral fusion. However, phospholipids are not pharmacologically useful. We show here that a family of synthetic rigid amphiphiles of shape similar to such phospholipids, RAFIs (rigid amphipathic fusion inhibitors), inhibit the infectivity of several otherwise unrelated enveloped viruses, including hepatitis C and HSV-1 and -2 (lowest apparent IC 50 48 nM), with no cytotoxic or cytostatic effects (selectivity index > 3,000) by inhibiting the increased negative curvature required for the initial stages of fusion.lipid bilayer fusion | DNA virus | RNA virus | Sindbis virus | nucleosides