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Journal of Cell Science, Vol 111, Issue 15 2097-2108, Copyright © 1998 by Company of Biologists
JOURNAL ARTICLES |
S Yumura and Y Fukui
Department of Biology, Faculty of Science, Yamaguchi University, Yamaguchi 753-8512, Japan.
To study the spatial and temporal regulation of the actin cytoskeleton, we have analyzed the actin concentration dynamics in live Dictyostelium. The relative actin concentration was analyzed with respect to cell behavior by fluorescence morphometry. We electroporated rhodamine-actin into Dictyostelium cells and acquired images with 200-300 millisecond temporal and approximately 250 nm spatial resolutions. To convert fluorescence intensity into actin concentration, the observation was made on nearly two-dimensional cells, and the actin signal was ratioed over a volume marker (FITC-BSA or GFP). Since the emission of FITC and GFP is pH-dependent, we first measured the cytoplasmic pH in live cells and determined that the pHi in pseudopods is same as that of general cytoplasm. During cytokinesis, the relative concentration of actin in the cleavage furrow was significantly higher than in the general cytoplasm. In migrating cells, actin was recruited surprisingly rapidly, particularly in the pseudopod. We found that the region of high actin concentration moves relative to the leading edge when a pseudopod projects or retracts. When the pseudopod retracts, the actin density dissipates within 5 seconds. We have also found that actin accumulates in developing pseudopods in an oscillatory manner, and this timing coordinates with advancement of the centroid. This is the first study to reveal the dynamic changes in relative concentration of actin in live cells and to quantitatively correlate these changes with the locomotive behavior of the amoeba.
This article has been cited by other articles:
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  Y. Iwadate and S. Yumura Actin-based propulsive forces and myosin-II-based contractile forces in migrating Dictyostelium cells J. Cell Sci., April 15, 2008; 121(8): 1314 - 1324. [Abstract] [Full Text] [PDF]
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 D. S. Kudryashov, M. Phillips, and E. Reisler Formation and Destabilization of Actin Filaments with Tetramethylrhodamine-Modified Actin Biophys. J., August 1, 2004; 87(2): 1136 - 1145. [Abstract] [Full Text] [PDF]
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K. S. K. Uchida and S. Yumura Dynamics of novel feet of Dictyostelium cells during migration J. Cell Sci., March 15, 2004; 117(8): 1443 - 1455. [Abstract] [Full Text] [PDF]
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K. S. K. Uchida, T. Kitanishi-Yumura, and S. Yumura Myosin II contributes to the posterior contraction and the anterior extension during the retraction phase in migrating Dictyostelium cells J. Cell Sci., January 1, 2003; 116(1): 51 - 60. [Abstract] [Full Text] [PDF]
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H Meinhardt Orientation of chemotactic cells and growth cones: models and mechanisms J. Cell Sci., January 9, 1999; 112(17): 2867 - 2874. [Abstract] [PDF]
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Y Fukui, T Kitanishi-Yumura, and S Yumura Myosin II-independent F-actin flow contributes to cell locomotion in dictyostelium J. Cell Sci., January 3, 1999; 112(6): 877 - 886. [Abstract] [PDF]
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