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MAMMALIAN SIALIDASE NEU3 OVEREXPRESSION IN COS-7 CELLS
CAUSES A DRASTIC DECREASE OF NDV-CELL FUSION AND VIRUS
INFECTIVITY
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F. D’Avila , L. Anastasia , A. Bianchi , N. Papini , C. Tringali , J. Holguera , E.
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Monti , E. Villar , I. Munoz Barroso , G. Tettamanti , B. Venerando
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Dip. di Chimica, Biochimica e Biotecnologie per la Medicina, Università degli Studi di
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Milano; Departamento de Bioquìmica y Biologìa Molecular, Universidad de
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Salamanca, Spain; Dip. di Scienze Biomediche e Biotecnologie, Università degli Studi
di Brescia
NDV (Newcastle Disease Virus) is an avian enveloped virus that belongs to the
Paramyxoviridae family. The interaction of enveloped viruses with cell surface
receptors is the first step in the viral cycle and an important determinant of viral host
range. Although it is established that NDV binds to sialic acid-containing
glycoconjugates, the exact nature of the receptors has not yet been determined.
However several independent studies have indicated that sialo-glycoconjugates, both
N-linked glycoproteins and gangliosides, seem to be essential for NDV fusion and
infectivity (1). Moreover NDV also interacts in vitro with different
monosialogangliosides, disialogangliosides, and trisialogangliosides that have sialic
acid residues attached to a terminal or an internal galactose (1). Gangliosides, together
with other sialo-glycoconjugates, are substrates of glycohydrolitic enzymes named
sialidases. In particular, the plasma membrane sialidase (NEU3) has gangliosides as its
preferred substrates. The overexpression of this sialidase in COS-7 cells leads to a
substantial modification of the ganglioside pattern in the cell plasma membrane,
accompanied by a marked decrease in ganglioside GD1a and GM3 (2).
Bearing all this in mind, we surmised that NEU3 overexpression in COS-7 cells might
interfere with the NDV-host cell membrane interaction. In fact, the important changes
observed in the sphingolipid pattern after NEU3 overexpression would alter some key
molecules for NDV binding and infection, including gangliosides.
NEU3 overexpression in COS7 cells not only dramatically reduced NDV fusion and
infectivity, but almost completely inhibited viral propagation through cell-cell fusion.
We also observed that NDV preferentially binds to detergent-resistant membranes
(DRMs), which are particularly enriched in gangliosides, and that the viral sialidase
can hydrolyze ganglioside GD1a present at the cell membrane.
(1) FerreiraL,et al., Int.J.Biochem.Cell.Biol. (2004)
(2) Papini et al., JBC (2004)