Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

35-POS Board 35 VISUALIZATION OF ENDOPLASMIC RETICULUM MEMBRANE TOPOLOGY BASED ON SUPER-RESOLUTION MICROSCOPY DATA Zach Marin 1,2 ; Michael Graff 1 ; Joerg Bewersdorf 1,2 ; David Baddeley 1,3 ; 1 Yale University, Cell Biology, New Haven, Connecticut, USA 2 Yale University, Biomedical Engineering, New Haven, Connecticut, USA 3 University of Auckland, Auckland Bioengineering Institute, Auckland, New Zealand Membrane fusion and fission processes within the endoplasmic reticulum (ER) are essential for maintaining the complex structure and function of this important organelle, but difficult to study due to the ER’s convoluted topology. The ER exhibits a broad continuum of morphologies ranging from flat, sheet-like domains to highly curved parking-garage structures, tubules, and nanoscale holes. The ER is also highly dynamic, and can transition between morphologies on a timescale of seconds to minutes. While many proteins that are key players in ER organization have been identified, the mechanisms of ER membrane fusion and fission are still poorly understood--it even seems likely that different fission and fusion mechanisms are active in different parts of the ER. Due to the structural heterogeneity in the ER, we believe that fusion and fission processes must be studied in the context of local membrane morphology. To enable this, we have developed super-resolution microscopy techniques that provide a detailed view of ER morphology and dynamics. Single-molecule switching nanoscopy (SMSN), in particular, provides 3D data at 20- nm resolution. Rather than directly imaging membrane surfaces, however, SMSN gives us the positions of proteins that localize to the ER membrane. Here, we present our work toward creating and visualizing biophysically-constrained representations of a membrane passing through an SMSN point cloud. These algorithms are implemented in the PYthon Microscopy Environment (PYME), an open-source nanoscopy imaging and analysis suite. This tool enables us to quantify the curvature of the ER membrane, which we can use to understand possible mechanisms of ER fusion events, and other membranous organelles.

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