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Biophysics of Proteins at Surfaces: Assembly, Activation, Signaling
Poster Abstracts
5-POS
Board 5
Septin Filaments Recognize Micron-Scale Positive Plasma Membrane Curvature
Andrew Bridges
, Patricia Occhipinti, Amy Gladfelter.
Dartmouth College, Hanover, USA.
Septins are conserved filament forming GTPases that maintain cell polarity by restricting
diffusion of proteins in the plasma membrane and endoplasmic reticulum while acting as a
molecular scaffold for cytosolic proteins. Septin higher-order structures form on and associate
with the plasma membrane and cells carrying mutated septin genes display irregular cell polarity,
abnormal cell shape, are defective at cytokinesis, and are generally inviable. Though it has been
shown that Cdc42 drives the accumulation of septins at incipient sites of cell polarity, properties
of the plasma membrane that influence and maintain their localization have not been established.
Here, we show that septins preferentially bind the plasma membrane in numerous cell types at
sites of micron-scale positive curvature, a common topology of polarized cells. In regions of the
cell devoid of positive curvature, septin filaments preferentially minimize interacting with
negative plasma membrane curvature. Using phospholipid bilayer coated glass microspheres we
show that curvature recognition is an intrinsic property of septin filaments. This work
demonstrates that septins are a filamentous system capable of sensing plasma membrane shape
on the micron-scale. Utilizing this property, septins respond to large scale changes in cell shape
and communicate these changes to the cytoplasm.