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Understanding the rhabdovirus fusion machinery

Perspectives opened by dynamic structural virology

Molecular and Structural Virology Laboratory CNRS – Gif sur Yvette

Yves Gaudin

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Rhabdovirus entry into the host cell

Endosome acidification

Membrane fusion

Virion endocytosis

Receptor recognition

Prototypes : rabies virus and VSV

Enveloped viruses with a typical bullet shape

Glycoprotein G mediates viral entry

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The membrane fusion pathwayComplete

fusion

Stalk Hemifusion Fusion Pore

Class IParamyxovirus F

Influenza HAHIV gp160

Class IIAlphavirus E1Flavivirus E

Native or prefusion conformation

Energy

Final or postfusion conformation

Fusion machineries

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Rhabdovirus glycoprotein G: The prototype of the third class

Internal fusion loops

Transmembrane domain

446 466 495CHO CHO

pH-dependent equilibrium between these different states

How does it work ?

Prefusion state

Activated state

Postfusion state

Receptor recognition

Membrane interaction

pH >7 pH < 6.5

pH 7.5 pH 5.5One glycoprotein

Several conformations

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pH 5.5pH 7.5

Identification of two distinct steps during membrane fusion

Libersou et al. J. Cell Biol. 2010

Visualization of individual fusion events

LIPO

LIPO

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Crystalline structures of VSV G

TM

Trimers

Prefusion Postfusion

Forme préfusion

Protomers

Prefusion Postfusion

Roche et al. Science 2006 ; Science 2007

Membrane

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Target membrane

Viral membrane

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The conformational change pathway

Trimeric prefusion

state(high pH)

Trimeric postfusion

state(low pH)

Fusion loopsTransmembrane domains

**

TomographyCristallography

TomographyCristallography

EMSAXS

Decreasing pH

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First structure of intermediates• Chandipura virus (outbreaks of deadly encephalitis in India)

Two different monomers in the asymetric unit !

1 1

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VSV G postfusion

Late intermediate

VSV G prefusion

Fusion loops.TM domains.

Early intermediate

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Structural virology: a french « savoir faire »

- Class II fusion proteins of Chikungunya virus (Felix Rey, Institut Pasteur)

- Replication complex of influenza and Mononegavirales, HIV structural biology (Rob Ruigrok, Winfried Weissenhorn, UVHCI, Grenoble)

- Replication complex of positive strand RNA viruses such as Dengue virus, West Nile virus, SARS coronavirus (Bruno Canard, AFMB, Marseille)

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Perspectives

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Powerful hybrid approaches (Cristallography, EM, SAXS, NMR…) in structural virology allow:

•Access to the dynamics of complex viral machineries

•Determination of the structure of intermediates that can constitute new targets for antiviral strategies