Tag: Membrane structure and assembly

Human ESCRT-III polymers assemble on positively curved membranes and induce helical membrane tube formation

The Endosomal Sorting Complex Required for Transport-III (ESCRT-III) is part of a conserved membrane remodeling machine. ESCRT-III employs polymer formation to catalyze inside-out membrane fission processes in a large variety of cellular processes, including budding of endosomal vesicles and enveloped viruses, cytokinesis, nuclear envelope reformation, plasma membrane repair, exosome formation, neuron pruning, dendritic spine maintenance, and preperoxisomal vesicle biogenesis.*

How membrane shape influences ESCRT-III polymerization and how ESCRT-III shapes membranes is yet unclear.*

In the article “Human ESCRT-III polymers assemble on positively curved membranes and induce helical membrane tube formation” Aurélie Bertin, Nicola de Franceschi, Eugenio de la Mora, Sourav Maity, Maryam Alqabandi, Nolwen Miguet, Aurélie di Cicco, Wouter H. Roos, Stéphanie Mangenot, Winfried Weissenhorn and Patricia Bassereau describe how human core ESCRT-III proteins, CHMP4B, CHMP2A, CHMP2B and CHMP3 are used to address this issue in vitro by combining membrane nanotube pulling experiments, cryo-electron tomography and Atomic Force Microscopy.*

The authors show that CHMP4B filaments preferentially bind to flat membranes or to tubes with positive mean curvature.*

The results presented in the article cited above underline the versatile membrane remodeling activity of ESCRT-III that may be a general feature required for cellular membrane remodeling processes.*

The authors provide novel insight on how mechanics and geometry of the membrane and of ESCRT-III assemblies can generate forces to shape a membrane neck.*

NanoWorld Ultra-Short AFM Cantilevers USC-F1.2-k0.15 were used for the High-speed Atomic Force Microscopy ( HS-AFM ) experiments presented in this article.*

Figure 1 from «Human ESCRT-III polymers assemble on positively curved membranes and induce helical membrane tube formation” by Aurélie Bertin et al.: CHMP4-ΔC flattens LUVs and binds preferentially to flat membranes or to membranes with a positive mean curvature. 1a CHMP4B-ΔC spirals observed by HS-AFM on a lipid bilayer. Scale bar: 50 nm. Please refer to the full article for the complete figure: https://rdcu.be/b5rOe
Figure 1 from «Human ESCRT-III polymers assemble on positively curved membranes and induce helical membrane tube formation” by Aurélie Bertin et al.:
CHMP4-ΔC flattens LUVs and binds preferentially to flat membranes or to membranes with a positive mean curvature.
1a CHMP4B-ΔC spirals observed by HS-AFM on a lipid bilayer. Scale bar: 50 nm.
Please refer to the full article for the complete figure: https://rdcu.be/b5rOe

*Aurélie Bertin, Nicola de Franceschi, Eugenio de la Mora, Sourav Maity, Maryam Alqabandi, Nolwen Miguet, Aurélie di Cicco, Wouter H. Roos, Stéphanie Mangenot, Winfried Weissenhorn and Patricia Bassereau
Human ESCRT-III polymers assemble on positively curved membranes and induce helical membrane tube formation
Nature Communications volume 11, Article number: 2663 (2020)
DOI: https://doi.org/10.1038/s41467-020-16368-5

Please follow this external link to read the full article: https://rdcu.be/b5rOe

Open Access The article “ Human ESCRT-III polymers assemble on positively curved membranes and induce helical membrane tube formation “ by Aurélie Bertin, Nicola de Franceschi, Eugenio de la Mora, Sourav Maity, Maryam Alqabandi, Nolwen Miguet, Aurélie di Cicco, Wouter H. Roos, Stéphanie Mangenot, Winfried Weissenhorn and Patricia Bassereau is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

High-speed AFM height spectroscopy reveals microsecond-dynamics of unlabeled biomolecules

In their recent publication “High-speed AFM height spectroscopy reveals μs-dynamics of unlabeled biomolecules” in Nature Communications George R. Heath and Simon Sheuring develop and apply HS-AFM height spectroscopy (HS-AFM-HS, a technique inspired by fluorescence spectroscopy), a technique whereby the AFM tip is held at a fixed x–y position and  the height fluctuations under the tip in z-direction with Angstrom spatial and 10µs temporal resolution are monitored.

They demonstrate “how this technique can be used to simultaneously measure surface concentrations, diffusion rates and oligomer sizes of highly mobile annexin-V molecules during membrane-binding and self-assembly at model membranes and derive its kinetic and energetic terms. Additionally, HS-AFM-HS at specific positions in the annexin lattice where the freedom of movement is restricted to rotation allowed determination of the interaction free energies of protein-protein contacts.”* The applicability of this technique is wide and is discussed at the end of the publication.

NanoWorld Ultra-Short Cantilevers (USC) for Fast-/High-Speed AFM  ( USC-F1.2-k0.15 ) were used.

Congratulations to the authors to this publication which pushes the speed limits of AFM even further!

Increasing the temporal resolution of HS-AFM by reducing the dimensionality of data acquisition. a HS-AFM image of a DOPC/DOPS (8:2) membrane in the presence of annexin-V and NP-EGTA-caged Ca2+. Blue arrows illustrate the slow- (vertical) and the fast-scan axis (horizontal). Images can be captured at up to 10–20 frames s−1. b HS-AFM movie frames of A5 membrane-binding, self-assembly and formation of p6 2D-crystals upon UV-illumination induced Ca2+-release. c Average height/time trace of the membrane area in b. d Averaged HS-AFM image of an A5 p6-lattice overlaid with the subsequent line scanning kymograph, obtained by scanning repeatedly the central x-direction line as illustrated by the blue arrow with a maximum rate of 1000–2000 lines s−1. e Line scanning kymograph across one protomer of the non-p6 trimer, marked by * in d and e at a rate of 417 lines s−1 (2.4 ms per line). f Histogram of state dwell-times of the molecule in e. g HS-AFM image of an A5 p6-lattice partially covering a DOPC/DOPS (8:2) SLB surface during self-assembly. HS-AFM height spectroscopy (HS-AFM-HS) is performed following halting the x- and y-piezos to capture height information at a fixed position at the center of the image (illustrated by the target). h Schematic showing the principle of HS-AFM-HS. The AFM tip is oscillated in z at a fixed x,y-position, detecting single molecule dynamics such as diffusion under the tip. i Height/time trace obtained by HS-AFM-HS with the tip positioned at the center of image (g). The height/time trace allows determination of the local A5 concentration analyzing the time fraction of the occurrence of height peaks. j Dwell-time analysis of each height peak of diffusing A5 from 60 s height/time data and subsequent fitting of the distribution to multiple Gaussians (possible molecular aggregates corresponding to the fits with distinct dwell-times (τD) are shown above the graph). All scale bars: 20 nm, NanoWorld Ultra-Short Cantilevers (USC) for Fast-/High-Speed AFM ( USC-F1.2-k0.15 ) were used.
Figure 1 from “High-speed AFM height spectroscopy reveals μs-dynamics of unlabeled biomolecules”: Increasing the temporal resolution of HS-AFM by reducing the dimensionality of data acquisition. a HS-AFM image of a DOPC/DOPS (8:2) membrane in the presence of annexin-V and NP-EGTA-caged Ca2+. Blue arrows illustrate the slow- (vertical) and the fast-scan axis (horizontal). Images can be captured at up to 10–20 frames s−1. b HS-AFM movie frames of A5 membrane-binding, self-assembly and formation of p6 2D-crystals upon UV-illumination induced Ca2+-release. c Average height/time trace of the membrane area in b. d Averaged HS-AFM image of an A5 p6-lattice overlaid with the subsequent line scanning kymograph, obtained by scanning repeatedly the central x-direction line as illustrated by the blue arrow with a maximum rate of 1000–2000 lines s−1. e Line scanning kymograph across one protomer of the non-p6 trimer, marked by * in d and e at a rate of 417 lines s−1 (2.4 ms per line). f Histogram of state dwell-times of the molecule in e. g HS-AFM image of an A5 p6-lattice partially covering a DOPC/DOPS (8:2) SLB surface during self-assembly. HS-AFM height spectroscopy (HS-AFM-HS) is performed following halting the x- and y-piezos to capture height information at a fixed position at the center of the image (illustrated by the target). h Schematic showing the principle of HS-AFM-HS. The AFM tip is oscillated in z at a fixed x,y-position, detecting single molecule dynamics such as diffusion under the tip. i Height/time trace obtained by HS-AFM-HS with the tip positioned at the center of image (g). The height/time trace allows determination of the local A5 concentration analyzing the time fraction of the occurrence of height peaks. j Dwell-time analysis of each height peak of diffusing A5 from 60 s height/time data and subsequent fitting of the distribution to multiple Gaussians (possible molecular aggregates corresponding to the fits with distinct dwell-times (τD) are shown above the graph). All scale bars: 20 nm

*George R. Heath & Simon Scheuring
High-speed AFM height spectroscopy reveals μs-dynamics of unlabeled biomolecules
Nature Communicationsvolume 9, Article number: 4983 (2018)
DOI: https://doi.org/10.1038/s41467-018-07512-3

Please follow this external link for the full article: https://rdcu.be/bdaKU

Open Access The article “High-speed AFM height spectroscopy reveals μ s-dynamics of unlabeled biomolecules” by George R. Heath & Simon Scheuring is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.