Micron-scale plasma membrane curvature is recognized by the septin cytoskeleton

Abstract

Cells change shape in response to diverse environmental and developmental conditions, creating topologies with micron-scale features. Although individual proteins can sense nanometer-scale membrane curvature, it is unclear if a cell could also use nanometer-scale components to sense micron-scale contours, such as the cytokinetic furrow and base of neuronal branches. Septins are filament-forming proteins that serve as signaling platforms and are frequently associated with areas of the plasma membrane where there is micron-scale curvature, including the cytokinetic furrow and the base of cell protrusions. We report here that fungal and human septins are able to distinguish between different degrees of micron-scale curvature in cells. By preparing supported lipid bilayers on beads of different curvature, we reconstitute and measure the intrinsic septin curvature preference. We conclude that micron-scale curvature recognition is a fundamental property of the septin cytoskeleton that provides the cell with a mechanism to know its local shape.

Fungal Morphogenesis, from the Polarized Growth of Hyphae to Complex Reproduction and Infection Structures

“…Thus, the surface of endosomes is used for the assembly of heteromeric septin complexes, and these complexes are transported for the formation of higherorder structures (190). In accordance, the membrane-assisted assembly of heteromeric septin structures was recently shown, and septins were able to recognize specific membrane curvatures (191,192). Importantly, this is yet another new function of early endosomes: the transport of newly synthesized proteins and the assembly of heteromeric protein complexes.…”

Endosomal assembly and transport of heteromeric septin complexes promote septin cytoskeleton formation

“…An attractive explanation would be that, compared to single septin proteins, heterooligomers bind endosomal lipids stronger. This could be due to an increased avidity of membrane binding, for example, mediated by the multiplication of polybasic regions in septin oligomers, or the ability of septin oligomers to recognize membrane curvature (Bridges et al, 2016). Alternatively, an interaction partner that specifically interacts with the C-termini of Cdc3 and Cdc12 might be present.…”

Forging the ring: from fungal septins' divergent roles in morphology, septation and virulence to factors contributing to their assembly into higher order structures

“…Ash. gossypii Cdc11a was found to localize asymmetrically at the branching sites, with the most highly curved side of the branch point enriched (Bridges et al, 2016). Septins have a preference for positive curvature (the base of branches), while in areas of negative curvature (hyphal cell), septins localize parallel to the hyphal growth Morphogenesis, filamentous growth, teliospore formation Alvarez-Tabares & Perez-Martin (2010) axis.…”

“…Septin interactants, such as Hsl7 in Ash. gossypii, can discriminate between septins in the curved or straight surface, providing a mechanism for the cell to recognize micro-scale curvature (Bridges et al, 2016;Helfer & Gladfelter, 2006).…”