Endosome-to-cytosol transport of viral nucleocapsids.
During viral infection, fusion of the viral envelope with endosomal membranes and nucleocapsid release were thought to be concomitant events. We show here that for the vesicular stomatitis virus they occur sequentially, at two successive steps of the endocytic pathway. Fusion already occurs in transport intermediates between early and late endosomes, presumably releasing the nucleocapsid within the lumen of intra-endosomal vesicles, where it remains hidden. Transport to late endosomes is then required for the nucleocapsid to be delivered to the cytoplasm. This last step, which initiates infection, depends on the late endosomal lipid lysobisphosphatidic acid (LBPA) and its putative effector Alix/AIP1, and is regulated by phosphatidylinositol-3-phosphate (PtdIns3P) signalling via the PtdIns3P-binding protein Snx16. We conclude that the nucleocapsid is exported into the cytoplasm after the back-fusion of internal vesicles with the limiting membrane of late endosomes, and that this process is controlled by the phospholipids LBPA and PtdIns3P and their effectors.
Le Blanc
Isabelle
I
Biochemistry Department, University of Geneva, 30 quai E. Ansermet, 1211 Geneva 4, Switzerland.
Luyet
Pierre-Philippe
PP
Pons
Véronique
V
Ferguson
Charles
C
Emans
Neil
N
Petiot
Anne
A
Mayran
Nathalie
N
Demaurex
Nicolas
N
Fauré
Julien
J
Sadoul
Rémy
R
Parton
Robert G
RG
Gruenberg
J
J
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002417:Cattle; D002460:Cell Line; D006224:Cricetinae; D003600:Cytosol / Q000378:metabolism* / Q000648:ultrastructure; D056827:Endosomal Sorting Complexes Required for Transport; D011992:Endosomes / Q000378:metabolism* / Q000648:ultrastructure; D004847:Epithelial Cells / Q000821:virology; D005347:Fibroblasts / Q000821:virology; D006367:HeLa Cells; D006801:Humans; D008246:Lysophospholipids / Q000502:physiology; D008561:Membrane Fusion / Q000187:drug effects / Q000502:physiology*; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D050178:Monoglycerides; D019251:Nucleocapsid / Q000378:metabolism*; D018129:Phosphatidylinositol Phosphates / Q000502:physiology; D010750:Phosphoproteins / Q000235:genetics / Q000502:physiology; D012367:RNA, Viral / Q000096:biosynthesis / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D058305:Sorting Nexins; D013997:Time Factors; D022161:Transport Vesicles / Q000378:metabolism / Q000648:ultrastructure; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000502:physiology; D014721:Vesicular stomatitis Indiana virus / Q000502:physiology; D014779:Virus Replication / Q000235:genetics
D056827:Endosomal Sorting Complexes Required for Transport; D008246:Lysophospholipids; D050178:Monoglycerides; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; D012367:RNA, Viral; C477748:SNX16 protein, human; D058305:Sorting Nexins; D033921:Vesicular Transport Proteins; C012786:bis(monoacylglyceryl)phosphate; C096164:hepatocyte growth factor-regulated tyrosine kinase substrate; C055525:phosphatidylinositol 3-phosphate