Sorting of Marburg Virus Surface Protein and Virus Release Take Place at Opposite Surfaces of Infected Polarized Epithelial Cells

Abstract

Marburg virus, a filovirus, causes severe hemorrhagic fever with hitherto poorly understood molecular pathogenesis. We have investigated here the vectorial transport of the surface protein GP of Marburg virus in polarized epithelial cells. To this end, we established an MDCKII cell line that was able to express GP permanently (MDCK-GP). The functional integrity of GP expressed in these cells was analyzed using vesicular stomatitis virus pseudotypes. Further experiments revealed that GP is transported in MDCK-GP cells mainly to the apical membrane and is released exclusively into the culture medium facing the apical membrane. When MDCKII cells were infected with Marburg virus, the majority of GP was also transported to the apical membrane, suggesting that the protein contains an autonomous apical transport signal. Release of infectious progeny virions, however, took place exclusively at the basolateral membrane of the cells. Thus, vectorial budding of Marburg virus is presumably determined by factors other than the surface protein.

Multivesicular Bodies as a Platform for Formation of the Marburg Virus Envelope

“…It has been published earlier that MARV GP is released into the supernatant of GP-expressing cells (43). A recent study by Swenson et al confirmed this observation and, in addition, showed that the amount of GP released from the cells was increased by coexpression of the viral matrix protein VP40 (47).…”

“…In MARV-infected polarized MDCK cells, the majority of GP was also transported to the apical membrane; however, the release of infectious progeny virions took place exclusively at the basolateral membrane of the cells. Thus, in the presence of other viral proteins, GP obviously is redirected to an alternative route (43). Another observation indicating a different route of GP transport in the context of the viral infection is intracellular budding of MARV in human macrophages (15).…”

“…During its transport to the Golgi apparatus, GP is subjected to acylation at two cysteine residues at the border between the membrane anchor and the cytoplasmic tail (19). Serine residues of the ectodomain of GP are phosphorylated in the Golgi apparatus (43). In the trans-Golgi network (TGN), GP is cleaved by the prohormone convertase furin into two subunits, GP 1 (170 kDa) and GP 2 (46 kDa), that are linked by disulfide bonds (49).…”

Nipah Virus Entry and Egress from Polarized Epithelial Cells

“…However, the localization of G and F proteins in infected polarized MDCK cells was found to be bipolar, with most of the glycoproteins concentrating at the apical membrane (27). As it is known for several viruses that the glycoprotein distribution does not necessarily determine the site of virus budding (28)(29)(30)(31), the impact of the NiV glycoprotein distribution is not yet known. The aim of this study was thus to elucidate the virus entry and exit pathways in polarized epithelial cells and to clarify the role of vectorial sorting of the NiV envelope proteins in virus spread and release from epithelial cells.…”

Glycoprotein targeting signals influence the distribution of measles virus envelope proteins and virus spread in lymphocytes

“…Thus, transient polarization of lymphocytes, similar to the permanent polarized nature of epithelia or neurons, is not only central to their physiological function, but also influences virus replication. Selective transport of viral surface and matrix proteins to a specific domain can critically determine cell-to-cell spread and targeted virus release from polarized cells (Danis et al, 2004;Deschambeault et al, 1999;Fuller et al, 1984;Lodge et al, 1997;Mora et al, 2002;Sanger et al, 2001;Tashiro et al, 1990;Zimmer et al, 2002).…”