Efficient transport of Semliki Forest virus glycoproteins through a Golgi complex morphologically altered by Uukuniemi virus glycoproteins.

Abstract

In infected BHK21 cells, the glycoproteins G1 and G2 of a temperature‐sensitive mutant (ts12) of Uukuniemi virus (UUK) accumulate at 39 degrees C in the Golgi complex (GC) causing an expansion and vacuolization of this organelle. We have studied whether such an altered Golgi complex can carry out the glycosylation and transport to the plasma membrane (PM) of the Semliki Forest virus (SFV) glycoproteins in double‐infected cells. Double‐immunofluorescence staining showed that approximately 90% of the cells became infected with both viruses. Almost the same final yield of infectious SFV was obtained from double‐infected cells as from cells infected with SFV alone. The rate of transport from the endoplasmic reticulum (ER) via the GC to the plasma membrane of the SFV glycoproteins was analysed by immunofluorescence, surface radioimmunoassay and pulse‐chase labeling followed by immunoprecipitation, endoglycosidase H digestion and SDS‐PAGE. The results showed that: the SFV glycoproteins were readily transported to the cell surface in double‐infected cells, whereas the UUK glycoproteins were retained in the GC; the transport to the PM was retarded by approximately 20 min, due to a delay between the ER and the central Golgi; E1 of SFV appeared at the PM in a sialylated form. These results indicate that the morphologically altered GC had retained its functional integrity to glycosylate and transport plasma membrane glycoproteins.

Effect of caffeine and reduced temperature (20 degrees C) on the organization of the pre-Golgi and the Golgi stack membranes.

“…In Fig. 1 b, it can be seen that E1 does not become completely resistant to Endo H treatment even at 28~ This, however, is a constant finding for SFV ts-1 and has been reported and discussed earlier (Saraste and Kuismanen, 1984;Gahmberg et al, 1986).…”

The Cytoplasmic Tails of Uukuniemi Virus ( Bunyaviridae ) G N and G C Glycoproteins Are Important for Intracellular Targeting and the Budding of Virus-Like Particles

“…Both glycoproteins accumulated in the Golgi membrane but were unable to initiate budding, resulting in large vacuolization of the Golgi complex. The function of the Golgi complex remained intact, and at a lower temperature (32°C) virus particles could be produced (13,14). However, we did not observe an increase in VLP formation at lower temperatures, indicating that our FIG.…”

Molecular biology of the Bunyaviridae

“…The glycoproteins accumulate in the Golgi complex, causing a progressive vacuolization , an effect mediated by the glycoproteins alone (Gahmberg et al, 1986a). However, the morphologically altered Golgi complex remains functionally active, as evidenced by its ability to glycosylate and transport authentic plasma membrane glycoproteins (Gahmberg et al, 1986b). Virions bud into Golgi vesicles, which are transported to the cell surface where the particles are released by exocytosis.…”