How enzymes locally block cell wall repair, allowing cells to fuse in an irreversible manner
The fusion of two cells is a decisive event in the sexual reproduction of many organisms. In fungi, cells must not only bring their membranes together and merge them, but also locally open their protective cell wall.
In order to fuse, fungal cells must open and expand a pore in their protective cell wall. However, a mechanism that prevents cell wall repair at the fusion site can make the process irreversible. A new study published in Current Biology provides insight into how this mechanism works.
Researchers at the University of Geneva studied Schizosaccharomyces pombe, a type of yeast commonly used as a model organism for understanding cellular mechanisms, and identified the Pak2 enzyme as crucial for preventing wall repair during fusion. Pak2 accumulates at the fusion site in normal cells, promoting the opening and expansion of the pore that allows cellular contents to pass from one cell to the other.
However, when the Pak2 enzyme is absent, the cell wall repair mechanism can sometimes close the pore and rebuild the wall between the two cells, effectively reversing fusion. This reversal occurs because the mechanisms that monitor and repair the cell wall become particularly active at the fusion site in Pak2-deficient cells.
By understanding the balance between cell wall repair and localized degradation during fusion, this study opens new avenues for the development of antifungal strategies, as the cell wall is a major target for many treatments against pathogenic fungi.
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