The small hydrophobic (SH) protein accumulates within lipid-raft structures of the Golgi complex during respiratory syncytial virus infection

Abstract

The cellular distribution of the small hydrophobic (SH) protein in respiratory syncytial virus (RSV)-infected cells was examined. Although the SH protein was distributed throughout the cytoplasm, it appeared to accumulate in the Golgi complex within membrane structures that were enriched in the raft lipid, GM1. The ability of the SH protein to interact with lipid-raft membranes was further confirmed by examining its detergent-solubility properties in Triton X-100 at 4 6C. This analysis showed that a large proportion of the SH protein exhibited detergent-solubility characteristics that were consistent with an association with lipid-raft membranes. Analysis of virus-infected cells by immuno-transmission electron microscopy revealed SH protein clusters on the cell surface, but only very low levels of the protein appeared to be associated with mature virus filaments and inclusion bodies. These data suggest that during virus infection, the compartments in the secretory pathway, such as the endoplasmic reticulum (ER) and Golgi complex, are major sites of accumulation of the SH protein. Furthermore, although a significant amount of this protein interacts with lipid-raft membranes within the Golgi complex, its presence within mature virus filaments is minimal.

The Human Respiratory Syncytial Virus Matrix Protein Is Required for Maturation of Viral Filaments

“…There is ample evidence of a role for polymerized actin and actinregulatory proteins in assembly (4,6,11,22,30,32,49,53,59). However, the role of polymerized actin seems to be limited to the actual budding/release event (11,30,32), which was shown previously to occur at sites of lipid rafts (8,9,22,27,31,36,42,49,50). In contrast to polymerized actin, microtubules were reported previously to be involved in virus production at a step prior to budding (32).…”

“…Several reports have implicated cytoskeletal elements in the processes that lead to virus egress, in particular microtubules, myosin V, actin, and actin-regulatory proteins such as profilin and RhoA (30,32,59). In addition, a role for an actin/myosinbased motility system in HRSV exit has been proposed (6,53,59), and there is strong evidence for the involvement of lipid rafts (8,9,22,27,31,36,49,50,53).…”

Structural and Functional Aspects of the Small Hydrophobic (SH) Protein in the Human Respiratory Syncytial Virus

“…Indeed, hRSV has been shown to utilize lipid rafts, and in particular caveolae, a caveolin-1 enriched subdomain (Werling et al, 1999;Brown et al, 2002), to gain entry and in the assembly of virus particles. Only a very low amount of SH protein is associated with the viral envelope (Rixon et al, 2004).…”

“…During infection, the majority of the SH protein accumulates at lipid-raft structures of the Golgi complex, the endoplasmic reticulum (ER), and the cell surface (Rixon et al, 2004). Lipid rafts are enriched in cholesterol and sphingolipids and form a platform for various protein-protein interactions necessary during signal transduction events (Dykstra et al, 2003), protein trafficking (Helms & Zurzolo, 2004), and also virus entry, assembly, and budding (Suzuki & Suzuki, 2006).…”

Pentameric viral ion channels: from structure to function

“…72 During infection, the full-length unmodified form is the major species. 68 RSV lacking the SH gene (RSV∆SH) is viable, causes formation of syncytia, and grows as well as the WT virus in cell culture.…”