Abstract
ABSTRACTCells are always subjected to mechanical stresses, resulting in wounds of the cell membrane, but cells are able to repair and reseal their wounded membrane. Previous reports have shown that actin and myosin II accumulate around the wound and that the constriction of this purse-string closes the membrane pore. Here, we developed a microsurgical wound assay to assess wound repair in Dictyostelium cells. Fluorescent dye that had been incorporated into the cells leaked out for only 2–3 sec after wounding, and a GFP-derived, fluorescent Ca2+ sensor showed that intracellular Ca2+ transiently increased immediately after wounding. In the absence of external Ca2+, the cell failed to repair itself. During the repair process, actin accumulated at the wounded sites but myosin II did not. The wounds were repaired even in myosin II null cells to a comparable degree as the wild-type cells, suggesting that myosin II does not contribute to wound repair. Thus, the actomyosin purse-string constriction model is not a common mechanism for wound repair in eukaryotic cells, and this discrepancy may arise from the difference in cell size.
Highlights
Cells are always subjected to mechanical or chemical damages from the environment, and often the cell membrane is wounded
We developed a microsurgical wound assay in Dictyostelium cells
Actin accumulated at the wound sites but myosin II did not
Summary
Cells are always subjected to mechanical or chemical damages from the environment, and often the cell membrane is wounded. Cells in mechanically active tissues, such as muscle cells, are frequently wounded; they seem to have the ability to repair their wounded cell membrane (Abreu-Blanco et al, 2011a; Idone et al, 2008a; McNeil and Steinhardt, 2003; Sonnemann and Bement, 2011; Steinhardt, 2005). Plant cells suffer from freeze-induced cell membrane wounds in winter, and their tolerance to freezing involves Ca2+-dependent membrane resealing. Artificial wound experiments, such as puncturing by a microneedle, ablation by intense laser illumination, or treatment with detergent, bacterial toxin, or hypotonic media have shown that mammalian cells, amphibian eggs, echinoderm eggs, fruit flies, amoebae, and budding yeast can reseal their cell membranes
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