S. Becker et al., INTRACELLULAR-TRANSPORT AND PROCESSING OF THE MARBURG VIRUS SURFACE PROTEIN IN VERTEBRATE AND INSECT CELLS, Virology, 225(1), 1996, pp. 145-155
The surface protein (GP) of Marburg virus (MEG) is synthesized as a 90
-kDa precursor protein which is cotranslationally modified by the addi
tion of high-mannose sugars (140 kDa). This step is followed by the co
nversion of the N-linked sugars to endoglycosidase H (endo H)-resistan
t species and the addition of O-linked oligosaccharides leading to a m
ature protein of 170-200 kDa approximately 30 min after pulse labeling
. The mature form of GP is efficiently transported to the plasma membr
ane. GP synthesized using the T7 polymerase-driven vaccinia virus expr
ession system was transported with essentially the same kinetics as th
e authentic GP. However, the protein that is shown to appear 30 min af
ter pulse labeling at the plasma membrane was slightly smaller (160 kD
a) than GP incorporated into the virions (170 kDa). Using a recombinan
t baculovirus, GP was expressed at high levels in insect cells. Three
different species could be identified: a 90-kDa unglycosylated GP loca
lized in the cytoplasm and two 140-kDa glycosylated proteins. Characte
rization of the glycosylated GPs revealed that processing of the oligo
saccharides of GP was less efficient in insect cells than in mammalian
cells. The majority of GP remained endo H sensitive containing high-m
annose type N-linked glycans, whereas only a small fraction became end
o H resistant carrying processed N-glycans and O-glycans. Tunicamycin
treatment of the GP-expressing cells demonstrated that N-glycosylation
is essential for the transport of the MBG surface protein. (C) 1996 A
cademic Press, Inc.