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Published on: September 13, 2018
Globoside Is an Essential Intracellular Factor Required for Parvovirus B19 Endosomal Escape
Jan Bieri1, Corinne Suter1,2, Oliver Caliaro1,2
1Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
Human parvovirus B19 (B19V) entry does not disrupt endosomes. Instead, globoside facilitates B19V escape via the Golgi, challenging previous models of viral entry.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Human parvovirus B19 (B19V) possesses phospholipase A2 (PLA2) activity, hypothesized to mediate viral entry through endosomal membrane disruption.
- The precise mechanism of B19V endosomal escape remains incompletely understood.
Purpose of the Study:
- To challenge the prevailing model of B19V entry.
- To elucidate the role of globoside and PLA2 activity in B19V cellular uptake and endosomal escape.
- To investigate the involvement of the Golgi apparatus in B19V infection.
Main Methods:
- Utilized globoside knockout cells to assess the necessity of globoside for B19V infection.
- Investigated B19V PLA2 activity under varying calcium and pH conditions.
- Employed MS2 bacteriophage particles pseudotyped with B19V PLA2 subunits to evaluate enzymatic function.
- Assessed endosomal integrity using microscopy during B19V entry.
- Examined the effect of polyethyleneimine (PEI) on rescuing infection in globoside-deficient cells.
- Analyzed the colocalization of incoming virus with Golgi markers.
Main Results:
- B19V entry occurs without endosomal disruption, with PLA2 activity optimized at specific calcium levels and pH found outside endosomes.
- Endosomal membrane integrity is maintained during B19V entry, even with high viral PLA2 enzymatic potential.
- Globoside is essential for B19V endosomal escape; its absence arrests viral entry within endosomes.
- Infection can be rescued by promoting endosomal leakage, confirming globoside's role in escape.
- B19V entry involves the Golgi apparatus, suggesting this organelle provides favorable conditions for PLA2 activity.
Conclusions:
- The current model of B19V entry via endosomal disruption is challenged.
- Globoside acts as a crucial intracellular receptor facilitating B19V endosomal escape.
- B19V entry involves retrograde transport to the Golgi, which supports the virus's lipolytic PLA2 activity for egress.
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