Directed motility of phagosomes in Tetrahymena thermophila requires actin and Myo1p, a novel unconventional myosin.
The phagosome cycle was investigated in Tetrahymena thermophila, which had internalized fluorescent latex beads. Confocal microscopy of cells from a GFP-actin strain revealed actin filaments that extended 3-5 mum from the periphery of fluorescent phagosomes. In GFP-actin cells and in wild-type cells, motility of fluorescent phagosomes was directed from the oral cavity to the posterior end of the cell. Although 60% of fluorescent phagosomes in the MYO1-knockout strain were motile, movement of phagosomes was not directed toward the posterior end of the cell and was random. Forty percent of fluorescent phagosomes in knockout cells were non-motile in contrast to only 20% non-motile phagosomes in wild-type cells. The increased incidence of non-motile phagosomes in the knockout strain could reflect absence of Myo1p as a motor. Another myosin or other molecular motors could power random movement of phagosomes in the MYO1-knockout strain. In latrunculin-treated GFP-actin cells, movement of fluorescent phagosomes was random. Average velocity of random movement of fluorescent phagosomes in the knockout strain and in latrunculin-treated cells was statistically the same as the average velocity (2.0 +/- 1.9 microm/min) of phagosomes in GFP-actin cells. These findings are an indication that dynamic actin and Myo1p are required for directed motility of phagosomes.
Hosein
Roland E
RE
Department of Biology, Brooklyn College of the City University of New York, Brooklyn, New York 11210, USA.
Williams
Selwyn A
SA
Gavin
R H
RH
D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D000970:Antineoplastic Agents / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D016764:Cell Polarity; D018613:Microscopy, Confocal; D008863:Microspheres; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*; D015739:Nocodazole / Q000494:pharmacology; D010588:Phagosomes / Q000187:drug effects / Q000378:metabolism*; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016808:Tetrahymena thermophila / Q000166:cytology* / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
D000199:Actins; D000970:Antineoplastic Agents; D019086:Bridged Bicyclo Compounds, Heterocyclic; C491829:MYO1 protein, protozoan; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D013844:Thiazoles; D053778:Thiazolidines; D018995:Myosin Heavy Chains; D015739:Nocodazole; C037067:latrunculin A