Interaction of α-Synuclein with Negatively Charged Lipid Membranes Monitored by Surface Plasmon Resonance

Aggregation of presynaptic protein α-synuclein is implicated in the development of Parkinson’s disease. Interaction of α-synuclein with lipid membranes appears to be critical for its physiological and pathological roles. Anionic lipids trigger conformational transition of α-synuclein from its natively disordered into an α-helical structure. Here we used surface plasmon resonance (SPR) to determine the affinities of α-synuclein for the small unilamellar vesicles composed of anionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS) or 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) and neutral 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) lipids. α-Synuclein bound in a concentration dependent manner to equimolar mixtures of POPC/POPS and POPC/DPPG vesicles. The affinity of α-synuclein for POPC/POPS was ~3-fold higher than for POPC/DPPG. These results indicate that headgroup charge is not the only factor contributing to α-synuclein-membrane association. This work is licensed under a Creative Commons Attribution 4.0 International License

An oomycete NLP cytolysin forms transient small pores in lipid membranes

Microbial plant pathogens secrete a range of effector proteins that damage host plants and consequently constrain global food production. Necrosis and ethylene-inducing peptide 1-like proteins (NLPs) are produced by numerous phytopathogenic microbes that cause important crop diseases. Many NLPs are cytolytic, causing cell death and tissue necrosis by disrupting the plant plasma membrane. Here, we reveal the unique molecular mechanism underlying the membrane damage induced by the cytotoxic model NLP. This membrane disruption is a multistep process that includes electrostatic-driven, plant-specific lipid recognition, shallow membrane binding, protein aggregation, and transient pore formation. The NLP-induced damage is not caused by membrane reorganization or large-scale defects but by small membrane ruptures. This distinct mechanism of lipid membrane disruption is highly adapted to effectively damage plant cells.Peer reviewe

α-Synuclein interactions with phospholipid model membranes: Key roles for electrostatic interactions and lipid-bilayer structure

Abstractα-Synuclein is a small presynaptic protein that is critically implicated in the onset of Parkinson's disease and other neurodegenerative disorders. It has been assumed that the pathogenesis of α-synuclein is associated with its aggregation, while for its physiological function, binding of α-synuclein to the synaptic vesicle membrane appears to be most important. The present study investigated the mechanism of α-synuclein binding to the lipid membrane. Upon binding to negatively charged small unilamellar vesicles consisting of 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol in the liquid-crystalline state, α-synuclein undergoes conformational transition from its native unfolded form to an α-helical structure. The positively charged N-terminal part of α-synuclein is likely to be involved in interactions with the negatively charged lipid surface. α-Synuclein did not associate with vesicles consisting of the zwitterionic (neutral) lipids 1,2-dipalmitoyl-sn-glycero-3-phosphocholine or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine. The data obtained by circular dichroism spectroscopy, fluorescence anisotropy measurements, differential scanning calorimetry, and calcein efflux assays indicate that in addition to electrostatic interactions, hydrophobic interactions are important in the association of α-synuclein with membranes. The mechanism of α-synuclein binding to lipid membranes is primarily dependent on the surface charge density of the lipid bilayer and the phase state of the lipids. We propose that α-synuclein has a lipid ordering effect and thermally stabilises vesicles

High-frequency and high-voltage asymmetric bipolar pulse generator for electroporation based technologies and therapies

Currently, in high-frequency electroporation, much progress has been made but limited to research groups with custom-made laboratory prototype electroporators. According to the review of electroporators and economic evaluations, there is still an area of pulse parameters that needs to be investigated. The development of an asymmetric bipolar pulse generator with a maximum voltage of 4 kV and minimum duration time of a few hundred nanoseconds, would enable in vivo evaluation of biological effects of high-frequency electroporation pulses. Herein, from a series of most commonly used drivers and optical isolations in high-voltage pulse generators the one with optimal characteristics was used. In addition, the circuit topology of the developed device is described in detail. The developed device is able to generate 4 kV pulses, with theoretical 131 A maximal current and 200 ns minimal pulse duration, the maximal pulse repetition rate is 2 MHz and the burst maximal repetition rate is 1 MHz. The device was tested in vivo. The effectiveness of electrochemotherapy of high-frequency electroporation pulses is compared to “classical” electrochemotherapy pulses. In vivo electrochemotherapy with high-frequency electroporation pulses was at least as effective as with “classical” well-established electric pulses, resulting in 86% and 50% complete responses, respectively. In contrast to previous reports, however, muscle contractions were comparable between the two protocols