Cell Biology

Staged Transport

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Science  08 Aug 2003:
Vol. 301, Issue 5634, pp. 735
DOI: 10.1126/science.301.5634.735c

When an influenza virus infects a cell, it enters via endocytosis at clathrin-coated pits. After these pits pinch off from the plasma membrane, the clathrin-coated vesicles lose their coats in the cytoplasm and then fuse with each other to form early endosomes, which subsequently mature into late endosomes. During these stages, the pH in the lumen of the endosome falls from about 7.0 to about 5.5, at which point the influenza hemagglutinin protein initiaties fusion of the viral envelope with the endosomal membrane, thereby releasing the viral capsid into the cytosol where it can establish a productive infection.

Lakadamyali et al. have been able to track the characteristics of single viral particles in real time by first fluorescently labeling them. After internalization, individual viruses appear to undergo an early active transport process that precedes viral fusion. The first stage of movement is actin-mediated, whereas subsequent stages involve the microtubule motor dynein and end with the virally loaded endosome in the perinuclear region, where the pH-triggered fusion occurs. — SMH

Proc. Natl. Acad. Sci. U.S.A. 100, 9280 (2003).

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