Abstract
The role of cell membrane dynamics in cell migration is unclear. To examine whether total cell surface area changes are required for cell migration, Dictyostelium cells were flattened by agar-overlay. Scanning electron microscopy demonstrated that flattened migrating cells have no membrane reservoirs such as projections and membrane folds. Similarly, optical sectioning fluorescence microscopy showed that the cell surface area does not change during migration. Interestingly, staining of the cell membrane with a fluorescent lipid analogue demonstrated that the turnover rate of cell membrane is closely related to the cell migration velocity. Next, to clarify the mechanism of cell membrane circulation, local photobleaching was separately performed on the dorsal and ventral cell membranes of rapidly moving cells. The bleached zones on both sides moved rearward relative to the cell. Thus, the cell membrane moves in a fountain-like fashion, accompanied by a high membrane turnover rate and actively contributing to cell migration.
Highlights
Cell migration plays important roles in many cellular processes, such as morphogenesis, immune responses, and wound healing
Internalization of the cell membrane stained with a fluorescent lipid analogue (FM1-43) revealed a 4–10 min turnover time in vegetative cells, which may be reasonable to explain the contribution of cell membrane turnover to cell migration[13]
We demonstrate that the cell membrane flows rearward, as the fountain flow model assumes, and provide essential information regarding the mechanism of cell migration
Summary
Cell migration plays important roles in many cellular processes, such as morphogenesis, immune responses, and wound healing. Internalization of the cell membrane stained with a fluorescent lipid analogue (FM1-43) revealed a 4–10 min turnover time in vegetative cells, which may be reasonable to explain the contribution of cell membrane turnover to cell migration[13] These authors examined cells in a vegetative stage, where the cells actively eat the external nutrient medium. In the fountain flow model (Fig. 1B), both the dorsal and ventral membranes flow toward the rear of migrating cells; membrane precursor vesicles are fused to the anterior cell membrane to supply new membrane lipids, and at the rear, membrane is removed by internalization. In the caterpillar flow model (Fig. 1C), the cell membrane moves circularly in the order of the ventral, anterior, dorsal, and rear regions In this case, the cell membrane may turn over everywhere. Due to a technical limitation at that time, the photobleaching was simultaneously performed on both the dorsal and ventral cell membrane in single cells, and the individual movements could not be distinguished
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