Cell Biology

Tale of Comet Tails

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Science  25 Feb 2000:
Vol. 287, Issue 5457, pp. 1365
DOI: 10.1126/science.287.5457.1365f

The intracellular pathogen, Listeria monocytogenes, travels through cells by nucleating the assembly of actin tails; these invading bacteria usurp existing cellular machinery to generate these spectacular comet-like structures. Intracellular organelle movements, however, are generally thought to occur along well-organized microtubule tracks.

Taunton et al. were studying the behavior of actin in living Xenopus eggs and observed the formation of actin tails on certain cytoplasmic vesicles soon after the eggs had been ‘activated’—the cellular equivalent of fertilization. The tail-forming activity was reconstituted in a cell-free system and involved the same set of proteins known to be involved in the formation of tails on invading pathogens—a process that previously had been reconstituted from purified components by Loisel et al. Subsequent analysis suggested that the cytoplasmic vesicles were multivesicular endosomes, and when mammalian endosomes and lysosomes were added to the frog system, they recruited the actin tail machinery and moved about. Merrifield et al. also have observed actin tails on pinocytic vesicles in cultured mast cells.—SMH

J. Cell Biol.148, 519 (2000); Nature401, 613 (1999); Nature Cell Biol.1, 72 (1999).

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