1. Understanding the rhabdovirus fusion machinery Perspectives opened by dynamic structural virology Molecular and Structural Virology Laboratory CNRS – Gif sur Yvette Yves Gaudin CEA CHRU CNRS CPU INRA INRIA INSERM INSTITUT PASTEUR IRD

2. Rhabdovirus entry into the host cell Prototypes : rabies virus and VSV Enveloped viruses with a typical bullet shape Glycoprotein G mediates viral entry Endosome acidification Membrane fusion Virion endocytosis Receptor recognition

3. The membrane fusion pathway Complete fusion Stalk Hemifusion Fusion Pore Class I Paramyxovirus F Influenza HA HIV gp160 Class II Alphavirus E1 Flavivirus E Native or prefusion conformation Energy Final or postfusion conformation Fusion machineries

4. Rhabdovirus glycoprotein G: The prototype of the third class How does it work ? Internal fusion loops Transmembrane domain 446 466 495 CHO CHO pH-dependent equilibrium between these different states Prefusion state Activated state Postfusion state Receptor recognition Membrane interaction pH >7 pH < 6.5 pH 7.5 pH 5.5 One glycoprotein Several conformations

6. Crystalline structures of VSV G TM Trimers Prefusion Postfusion Roche et al. Science 2006 ; Science 2007 Membrane Forme préfusion Protomers Prefusion Postfusion

7. Target membrane Viral membrane

8. The conformational change pathway Trimeric prefusion state (high pH) Trimeric postfusion state (low pH) Fusion loops Transmembrane domains * * Tomography Cristallography Tomography Cristallography EM SAXS Decreasing pH