Biophysical Society Thematic Meeting - October 13-15, 2015

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.

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