Understanding Periperal Membrane Protein Interactions | BPS Thematic Meeting

Understanding Peripheral Membrane Protein Interactions: Structure, Dynamics, Function and Therapy

Poster Abstracts

9-POS Board 9 MASS-SENSITIVE IMAGING OF MYOSIN-VI BOUND TO CARDIOLIPIN MEMBRANES USING ISCAT MICROSCOPY Nikolas Hundt 1,2 ; Antonino F Montanarella 1,2 ; Dominik Keim 1,2 ; Aron Venczel 1,2 ; Felix Zierhut 1,2 ; Simon Langnickel 1,2 ; Andreas Graw 1,2 ; Markus Kröss 1,2 ; Johannes Dietrich 1,2 ; Dario Saczko-Brack 1,2 ; Claudia Veigel 1,2 ; 1 Ludwig-Maximilians-Universität München, Cellular Physiology, Planegg-Martinsried, Germany 2 Ludwig-Maximilians-Universität München, Centre for NanoScience, Munich, Germany Studying protein-lipid interactions on near-physiological membrane systems is technically challenging as it involves the formation of model membranes and sensitive detection of their protein interaction. A large majority of techniques involves fluorescence for detecting protein and lipid components due to their superior signal specificity and a large toolkit to choose from. However, attachment of labels to lipids and proteins comes at the risk of changing the properties of the native system. For imaging of very fast processes, mediating transient interactions and diffusion phenomena, fluorescent dyes often lack the photon yield for sensitive high-speed imaging. Our lab has previously established an interferometric scattering (iSCAT) detection scheme for label-free, mass-sensitive imaging of single proteins on supported lipid bilayers. This technology enables native imaging of peripheral membrane proteins when bound to bilayers and studying their oligomeric state at millisecond time resolution. Using iSCAT, we have investigated the interaction of the molecular motor myosin-VI (Myo6) with cardiolipin (CL) membranes. CL is a specialized lipid of the inner mitochondrial membrane that gets externalized upon mitochondrial stress. Thereby, CL serves as a signal for cellular stress levels and mediates recycling of mitochondria through autophagy. The initiation of autophagy involves recruitment of Myo6 to mitochondria and formation of an actin cage around the organelle to isolate it from intact mitochondrial networks. The molecular steps that mediate recruitment of Myo6 to the membrane are unclear. We found that Myo6 interacts strongly with CL-containing membranes, gets activated as a motor and forms oligomeric assemblies capable of transporting cargo along actin filaments. Our mass-sensitive imaging helped us discern the lipid-binding and oligomer forming sections of Myo6 and create a model for its membrane-mediated activation, demonstrating the potential of iSCAT microscopy for peripheral membrane protein studies in general.

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