Two Septin Complexes Mediate Actin Dynamics During Cell Wound Repair.

Cell membranes are vulnerable to damage from mechanical and chemical insults. When breaches occur, cells initiate rapid repair processes to restore integrity. A key step involves forming and contracting an actomyosin ring at the wound site. While this mechanism is well-documented, the precise molecular regulators remain unclear. Septins, a family of cytoskeletal proteins, have been linked to actin organization in various contexts. However, their specific roles in wound repair have not been fully explored. This gap motivated researchers to investigate Septin function in this process. Prior studies have shown Septins influence actin structures in cell division and polarity. Yet, their involvement in wound healing remains understudied. This uncertainty drove the current investigation into Septin complexes during repair. No prior work had resolved the distinct roles of multiple Septin complexes in this setting.

This study aimed to clarify the role of Septin proteins in cell wound repair. Specifically, the researchers focused on how Septins regulate actomyosin ring dynamics. The study sought to determine whether multiple Septin complexes function during this process. By analyzing Septin recruitment patterns and mutant phenotypes, the team aimed to identify distinct functional roles. The goal was to understand how these complexes contribute to actin ring assembly and contraction. The researchers also wanted to explore interactions with other proteins like Anillin. This investigation was driven by the need to resolve the molecular mechanisms of wound repair. The study's findings could enhance understanding of cytoskeletal regulation in cellular injury.

The researchers used Drosophila as a model system to study Septin function during wound repair. They employed genetic tools to knock down or mutate individual Septin proteins. Fluorescent labeling allowed visualization of Septin localization at wound sites. Time-lapse imaging captured actomyosin ring formation and contraction dynamics. The team compared the effects of different Septin knockdowns on repair efficiency. They analyzed recruitment patterns to distinguish between Septin complexes. Functional assays measured F-actin bending activity for each complex. The study also examined Anillin's role in regulating Septin recruitment.

The study found that all five Drosophila Septins are essential for efficient wound repair. Two distinct Septin complexes, Sep1-Sep2-Pnut and Sep4-Sep5-Pnut, were identified. These complexes regulate different stages of actomyosin ring dynamics. The Sep1-Sep2-Pnut complex appears to influence ring assembly and contraction. The Sep4-Sep5-Pnut complex is involved in ring remodeling and stabilization. The two complexes differ in their F-actin bending activities. Anillin was shown to regulate the recruitment of only the Sep1-Sep2-Pnut complex. These findings suggest that Septin complexes work in parallel to control wound repair.

The authors propose that two Septin complexes function independently during wound repair. Each complex regulates specific aspects of actomyosin ring dynamics. The Sep1-Sep2-Pnut complex contributes to ring assembly and contraction. The Sep4-Sep5-Pnut complex plays a role in ring remodeling. The distinct F-actin bending activities suggest functional specialization. Anillin selectively regulates one of the two complexes. These findings support the idea that Septins work in parallel to control repair. The study highlights the importance of multiple Septin complexes in this process.