Organizing Large GTPase Atlastin-Mediated Membrane Fusion by Programmable DNA Origami Platforms

Area of Science:

• Cell Biology
• Biophysics
• Membrane Dynamics

Background:

• Eukaryotic cells use endoplasmic reticulum (ER) membrane fusion to create interconnected networks.
• Atlastins (ATLs) mediate ER fusion through GTP hydrolysis-induced conformational changes.
• The C-terminal amphipathic helix (AH_ATL-C) facilitates ATL function, but the cooperative mechanism of multiple ATLs remains unclear.

Purpose of the Study:

• To elucidate the cooperative mechanism of multiple atlastins (ATLs) in ER membrane tethering and fusion.
• To investigate the minimal ATL requirement for membrane tethering and lipid mixing.
• To understand the role of the AH_ATL-C in promoting membrane fusion.

Main Methods:

• Utilized programmable DNA origami rings for controlled proteoliposome generation with defined Drosophila ATL (dmATL) numbers.
• Employed DNA soccer-ball frameworks to create tethered liposomes for fusion studies.
• Combined molecular dynamics simulations with DNA-templated single-vesicle fusion assays.

Main Results:

• A single pair of dmATL molecules mediates membrane tethering but not lipid mixing.
• The AH_ATL-C is sufficient to promote membrane merging by enhancing bilayer fluctuations under specific lipid conditions.
• Demonstrated the functional role of dmATL in homotypic membrane fusion at the single-event level.

Conclusions:

• Provided mechanistic insights into dmATL-mediated homotypic membrane fusion.
• Highlighted the capability of the AH_ATL-C in driving membrane merging.
• Showcased adaptable DNA nanostructures as powerful tools for studying molecular interactions and membrane fusion.