The long and short of membrane curvature sensing by septins

Abstract

Septin proteins form hetero-oligomers that associate with membranes of specific curvatures, but the mechanism is unknown. In this issue, Cannon et al. (2019. J. Cell Biol. https://doi.org/10.1083/jcb.201807211) identify a single amphipathic helix that is necessary and sufficient for membrane curvature sensing by septins.

Animal Cell Cytokinesis: The Rho-Dependent Actomyosin-Anilloseptin Contractile Ring as a Membrane Microdomain Gathering, Compressing, and Sorting Machine

“…Septins have been shown to bind preferentially to membranes of a positive, micron-scale curvature ( Bridges et al, 2016 ; Beber et al, 2019 ; Cannon et al, 2019 ; McMurray, 2019 ). Although the CR undoubtedly harbor regions of changing membrane curvature, the Rho/Anillin-dependent recruitment of septins to the plasma membrane that we have observed occurs just as effectively in cells treated with LatA (where no such curvature exists) as in cells with a constricting actomyosin ring.…”

Nanoscale details of mitochondrial fission revealed by cryo-electron tomography

“…Their arrangement, frequently localized to the neck region of division bridges, differed from that of actin filaments, suggesting distinct roles. Septins are known to sense micron-scale membrane curvature (Bridges et al, 2016;McMurray, 2019), including at the poles of rod-shaped bacteria (Krokowski et al, 2018). It is therefore possible that the septin filaments we observed in our tomograms are sensing membrane curvature, if not driving remodeling directly, then perhaps reinforcing it by physically preventing the OMM from relaxing back to a larger diameter.…”

Simultaneous co‐overexpression of Saccharomyces cerevisiae septins Cdc3 and Cdc10 drives pervasive, phospholipid‐, and tag‐dependent plasma membrane localization

“…The septin complexes normally made during sporulation contain Cdc3 and Cdc10 but not Cdc12 or Shs1 (Garcia et al, 2016; McMurray & Thorner, 2008), and instead contain Spr28 and Spr3 (Garcia et al, 2016), the sporulation‐specific counterpart of Cdc12. Spr3 also has a predicted AH with unknown contributions to curvature preference (McMurray, 2019). Spr3 is required for uniform PM localization by Cdc3 in spores (Pablo‐Hernando et al, 2008) but since Spr3 is not expressed in vegetatively dividing cells, it cannot explain the BiFC PM localization we observe upon co‐overexpression of Cdc3 and Cdc10 in vegetative cells.…”

“…has a predicted AH with unknown contributions to curvature preference(McMurray, 2019). Spr3 is required for uniform PM localization by Cdc3 in spores(Pablo-Hernando et al, 2008) but since Spr3 is not expressed in vegetatively dividing cells, it cannot explain the BiFC PM localization we observe upon co-overexpression of Cdc3 and Cdc10 in vegetative cells.…”