The Lipidomes of Vesicular Stomatitis Virus, Semliki Forest Virus, and the Host Plasma Membrane Analyzed by Quantitative Shotgun Mass Spectrometry

Abstract

Although enveloped virus assembly in the host cell is a crucial step in the virus life cycle, it remains poorly understood. One issue is how viruses include lipids in their membranes during budding from infected host cells. To analyze this issue, we took advantage of the fact that baby hamster kidney cells can be infected by two different viruses, namely, vesicular stomatitis virus and Semliki Forest virus, from the Rhabdoviridae and Togaviridae families, respectively. We purified the host plasma membrane and the two different viruses after exit from the host cells and analyzed the lipid compositions of the membranes by quantitative shotgun mass spectrometry. We observed that the lipid compositions of these otherwise structurally different viruses are virtually indistinguishable, and only slight differences were detected between the viral lipid composition and that of the plasma membrane. Taken together, the facts that the lipid compositions of the two viruses are so similar and that they strongly resemble the composition of the plasma membrane suggest that these viruses exert little selection in including lipids in their envelopes.Enveloped viruses acquire their lipid envelope from the membranes of host cells (43). In this process, the nucleocapsid or the nucleocapsid-matrix complex of the viruses buds out of the cell and becomes enveloped by a segment of the host membrane. This membrane segment is modified during the budding process, such that virally encoded membrane proteins are included in the viral envelope, while most host proteins are excluded. Since viruses usually do not carry lipid-synthesizing enzymes, the lipids in the viral envelope are derived from the host membrane. The lipid compositions of enveloped viruses have been studied for years (2,15,17,18,23,25,34,36,38,40). One question that remains to be answered is whether the lipids are included passively, and thus the lipid composition of the envelope reflects the lipid composition of the host membrane, or whether lipid sorting occurs, leading to selective inclusion of some lipids and exclusion of others. This issue has been complicated by the fact that the lipid bilayer is no longer considered a homogenous liquid but contains fluctuating nanoscale assemblies of sphingolipids, saturated phospholipids, cholesterol (Chol), and proteins, called lipid rafts (13, 44). Lipid rafts can be induced to coalesce-usually by protein-protein interactions-into larger, dynamic platforms that function in signal transduction, intracellular membrane transport, and other membrane functions (45). It was also proposed that viruses make use of these membrane domains during their exit from cells (29, 32).A major complication in comparing viral envelopes with host cell membranes is the difficulty in obtaining host cell membranes of purity similar to that of the easily purified viruses. Many studies are faulted by the impurity of the cell membranes analyzed. Moreover, the early work in this field employed conventional analytical methods (such as thin-layer chromatography) t...

Biochemical and Morphological Properties of Hepatitis C Virus Particles and Determination of Their Lipidome

“…In contrast, hepatitis C virions resemble (V)LDL particles with respect to their high amounts of incorporated cholesteryl esters, which clearly set them apart from other viruses (51,61). However, it should be kept in mind that triacylglycerols (TAG), which are well established lipid components of HDL (6 mol %), LDL (10 mol %) and VLDL (60 mol %) (75) could not be determined due to technical difficulties.…”

“…Overall, polar membrane lipids such as phosphatidylserine and phosphatidylethanolamine that are enriched in HIV-1 (51), vesicular stomatitis virus, or Semliki Forest virus (61) are only minor lipids in hepatitis C virions. Along these lines, cholesterol, which is thought to be important especially for viruses that acquire their envelope from the plasma membrane, where cholesterol is most abundant, was well detectable in HCV particles but to lower concentrations than in other viruses (61). Likewise, sphingomyelin is enriched in HCV particles but again to a lower extent than reported for other viruses.…”

“…5, C and D). Although our analysis did not cover all possible lipids, most notably triacylglycerol that could not be quantified for technical reasons, the results suggest that the lipid composition of infectious HCV particles generated in Huh7.5 cells is similar to the one of LDL and VLDL (51,61,62).…”

High plasma level of nucleocapsid-free envelope glycoprotein-positive lipoproteins in hepatitis C patients

“…[12][13][14] Second, the phospholipid compositions of HCVcc and TRL share similar characteristics, whereas they strikingly differ from those of cellular membranes or envelopes of virus that assemble at cellular membranes. [15][16][17] Furthermore, lipoprotein lipases that specifically hydrolyse lipoprotein triacylglycerol modify HCVcc biochemical and physical features and decrease their infectivity. 18,19 Thus, both in vivo-produced and in vitro-produced HCV particles share many characteristics of lipoprotein association, but with differences in the extent of apoB association.…”

Lipid Involvement in Viral Infections: Present and Future Perspectives for the Design of Antiviral Strategies

“…For instance, flaviviruses (i.e. DENV or WNV) bud into the endoplasmic reticulum for acquisition of their envelope [80,82], while VSV (Figure 3), influenza, or HIV acquire their envelope by budding from plasma membrane [136][137][138][139]. In other cases, different cellular organelles can contribute with distinct membranes to virus envelopment, is reported for herpersvirus and poxvirus [140][141][142].…”