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F- and G-actin concentrations in lamellipodia of moving cells.
Koestler, Stefan A Rottner, Klemens Lai, Frank Block, Jennifer Vinzenz, Marlene Small, J Victor
Koestler, Stefan A
Rottner, Klemens
Lai, Frank
Block, Jennifer
Vinzenz, Marlene
Small, J Victor
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Abstract
Cells protrude by polymerizing monomeric (G) into polymeric (F) actin at the tip of the lamellipodium. Actin filaments are depolymerized towards the rear of the lamellipodium in a treadmilling process, thereby supplementing a G-actin pool for a new round of polymerization. In this scenario the concentrations of F- and G-actin are principal parameters, but have hitherto not been directly determined. By comparing fluorescence intensities of bleached and unbleached regions of lamellipodia in B16-F1 mouse melanoma cells expressing EGFP-actin, before and after extraction with Triton X-100, we show that the ratio of F- to G-actin is 3.2+/-0.9. Using electron microscopy to determine the F-actin content, this ratio translates into F- and G-actin concentrations in lamellipodia of approximately 500 microM and 150 microM, respectively. The excess of G-actin, at several orders of magnitude above the critical concentrations at filament ends indicates that the polymerization rate is not limited by diffusion and is tightly controlled by polymerization/depolymerization modulators.
Citation
F- and G-actin concentrations in lamellipodia of moving cells. 2009, 4 (3):e4810 PLoS ONE
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Article
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en
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1932-6203