Respiratory syncytial virus assembly occurs in GM1-rich regions of the host-cell membrane and alters the cellular distribution of tyrosine phosphorylated caveolin-1

Abstract

We have previously shown that respiratory syncytial virus (RSV) assembly occurs within regions of the host-cell surface membrane that are enriched in the protein caveolin-1 (cav-1). In this report, we have employed immunofluorescence microscopy to further examine the RSV assembly process. Our results show that RSV matures at regions of the cell surface that, in addition to cav-1, are enriched in the lipid-raft ganglioside GM1. Furthermore, a comparison of mock-infected and RSVinfected cells by confocal microscopy revealed a significant change in the cellular distribution of phosphocaveolin-1 (pcav-1). In mock-infected cells, pcav-1 was located at regions of the cell that interact with the extracellular matrix, termed focal adhesions (FA). In contrast, RSV-infected cells showed both a decrease in the levels of pcav-1 associated with FA and the appearance of pcav-1-containing cytoplasmic vesicles, the latter being absent in mock-infected cells. These cytoplasmic vesicles were clearly visible between 9 and 18 h post-infection and coincided with the formation of RSV filaments, although we did not observe a direct association of pcav-1 with mature virus. In addition, we noted a strong colocalization between pcav-1 and growth hormone receptor binding protein-7 (Grb7), within these cytoplasmic vesicles, which was not observed in mock-infected cells. Collectively, these findings show that the RSV assembly process occurs within specialized lipid-raft structures on the host-cell plasma membrane, induces the cellular redistribution of pcav-1 and results in the formation of cytoplasmic vesicles that contain both pcav-1 and Grb7.

Do lipid rafts mediate virus assembly and pseudotyping?

“…The viral glycoprotein and GM1 also co-localize on the cell surface. Respiratory syncytial virus has been shown to assemble within GM1-rich microdomains (Brown et al, 2002) and will form pseudotypes with VSV (Kahn et al, 1999(Kahn et al, , 2001). …”

Differential Regulation of GM1 and Asialo-GM1 Expression by T Cells and Natural Killer (NK) Cells in Respiratory Syncytial Virus Infection

“…At the level of the virus life cycle, RSV replication machinery colocalizes with lipid rafts, and virions are selectively assembled at and likely bud from lipid rafts (50)(51)(52)(53)(54). GM1 is incorporated into the RSV viral envelope (55).…”

Protein-Protein Interactions in RSV Assembly: Potential Targets for Attenuating RSV Strains

“…RSV buds from the lipid raft domains of the plasma membrane [11,12,54]. Analyses of the membranes from RSV-infected cells shows that all components of the nucleocapsid (N, P, L, M, M2-1) and envelope glycoprotein (M, F, G) complexes are present in the detergent insoluble lipid raft fraction [12,13,54].…”