Nanoscale architecture of F-BAR proteins and the Schizosaccharomyces pombe contractile ring

Abstract

Cytokinesis is the final step in the cell cycle where one cell is physically divided into two. Animal and fungal cells perform cytokinesis with an actin- and myosin-based molecular machine, the contractile ring. A complete list of components in the contractile ring has been determined in the model organism Schizosaccharomyces pombe; however, it remains unknown how these components organize into a functional division apparatus. Here, I have investigated how the F-BAR family of proteins organizes upon the plasma membrane in the contractile ring. I found the Cdc15 F-BAR forms extended linear oligomers that stably bind the plasma membrane in the contractile ring. These oligomers robustly concentrate Cdc15 at the division site and contribute to anchoring the contractile ring in the cell middle. I found the Imp2 F-BAR, similar to previously studied F-BARs, forms oligomerizes in a helical fashion. Despite this fact, Imp2 does not rely upon oligomerization for its contractile ring function. I have also determined the precise spatial organization of 29 components of the contractile ring with super resolution microscopy, and constructed a nanoscale model of the contractile ring that may serve as a template for understanding the ring’s inner mechanics.