Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

5-POS Board 5 COMPARATIVE ANALYSIS OF MEMBRANE CONSTRICTION BY DYNAMIN ISOFORMS Rebeca Bocanegra 1 ; Ariana Velasco 2,3 ; Sara de Lorenzo 1 ; Ormaetxea Julene 2,3 ; José L Carrascosa 1,5 ; Anna Shnyrova 2,3 ; Borja Ibarra 1 ; Vadim Frolov 2,3,4 ; 1 IMDEA Nanoscience, Madrid, Spain 2 Biofisika Institute (CSIC, UPV/EHU), Leioa, Vizcaya, Spain 3 University of the Basque Country, Biochemistry and Molecular Biology, Leioa, Vizcaya, Spain The proteins of dynamin superfamily are large GTPases widely implicated in fission and fusion of endomembranes. Their activity is necessary for internalizing essential nutrients, organelle transformations and maintenance, dynamins are intimately involved in signaling and membrane trafficking networks in the cell, in life and pathology. The superfamily founding members, dynamins 1 and 2 (Dyn1 and 2), remain the most characterized dynamins primarily involved in orchestrating membrane fission in the clathrin dependent endocytosis. As an endocytic vesicle buds, dynamin molecules are recruited to its neck, where it self-assembles a helical coat generating a dynamin-lipid tube. The helix constriction driven by GTP hydrolysis promotes fission of the neck and release of the vesicle. While the above patterns of dynamin activities common for Dyn1 and 2 are well understood, in vitro analyses revealed important functional differences between neuron-specific Dyn1 and ubiquitous Dyn2 isoforms. Here we performed systematic mechanistic comparison of membrane remodeling activities of Dyn1 and 2 reconstituted using lipid membrane nanotubes. By combining fluorescence microscopy and optical tweezers approaches, we quantified the nanotube constriction by dynamin isoform in apo state and in the presence of different nucleotide. Our analyses revealed significant differences between membrane constriction and curvature stabilization activities of Dyn1 and 2. We discuss possible relevance of these differences to physiological functions of the proteins. 4 Basque Foundation for Science, Bilbao, Vizcaya, Spain 5 National Center for Biotechnology (CSIC), Madrid, Spain

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