Newcastle disease virus may enter cells by caveolae-mediated endocytosis.
The entry into cells of Newcastle disease virus (NDV), a prototype member of the paramyxoviruses, is believed to occur by direct fusion at the plasma membrane through a pH-independent mechanism. In addition, NDV may enter host cells by an endocytic pathway. Treatment of cells with drugs that block caveolae-dependent endocytosis reduced NDV fusion and infectivity, the degree of inhibition being dependent on virus concentration. The inhibitory effect was reduced greatly when drugs were added after virus adsorption. Cells treated with methyl beta-cyclodextrin, a drug that sequesters cholesterol from membranes, reduced the extent of fusion, infectivity and virus-cell binding; this indicates that cholesterol plays a role in NDV entry. Double-labelling immunofluorescence assays performed with anti-NDV monoclonal antibodies and antibodies against the early endosome marker EEA1 revealed the localization of the virus in these intracellular structures. Using fluorescence microscopy, it was found that cell-cell fusion was enhanced at low pH. It is concluded that NDV may infect cells through a caveolae-dependent endocytic pathway, suggesting that this pathway could be an alternative route for virus entry into cells.
Cantín
Celia
C
Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain.
Holguera
Javier
J
Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain.
Ferreira
Laura
L
Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain.
Villar
Enrique
E
Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain.
Muñoz-Barroso
Isabel
I
Departamento de Bioquímica y Biología Molecular, Universidad de Salamanca, Edificio Departamental Lab. 108, Plaza Doctores de la Reina s/n, 37007 Salamanca, Spain.
D000818:Animals; D019556:COS Cells; D021941:Caveolae / Q000821:virology*; D002459:Cell Fusion; D002522:Chlorocebus aethiops; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008561:Membrane Fusion; D008856:Microscopy, Fluorescence; D009522:Newcastle disease virus / Q000472:pathogenicity* / Q000502:physiology; D014709:Vero Cells; D053586:Virus Internalization; D047392:beta-Cyclodextrins / Q000494:pharmacology
D047392:beta-Cyclodextrins; C031215:betadex