Tamucci, J. D. | Search bioRxiv

bioRxiv2025

Mitochondria-Targeted Peptides and Bilayer Composition Modulate Membrane Electro-poration Under Elevated Electrochemical Stress

Several studies have used molecular dynamics (MD) simulations to examine the relationship between transmembrane potentials ({Delta}{Psi}m) and electroporation; however, research on how this relationship presents in complex membranes with heterogenous lipid compositions is limited. Here we use all-atom, double-bilayer MD simulations with explicitly-modeled{Delta}{Psi} m voltages to compare how membranes with homogenous vs. heterogenous lipid compositions respond to varying degrees of electrochemical stress. These two bilayer systems were also exposed to a mitochondria-targeted peptide named Elamipretide which has been shown experimentally to modulate membrane electrostatics. Additionally, we used Computational Electrophysiology (CompEL) MD simulations to analyze how lipid composition and peptide exposure influence rates of passive transmembrane ion flux during electroporation events. The addition of cardiolipin (CL) and Elamipretide increased membrane capacitance, decreasing the{Delta}{Psi} m for a given transmembrane charge imbalance ({delta}TM) and protecting bilayers against electroporation. These results expand our understanding of how more complex, biologically-relevant bilayers respond to electrochemical stress.

biophysics↗

bioRxiv2019

Molecular Mechanism of Action of Mitochondrial Therapeutic SS-31 (Elamipretide): Membrane Interactions and Effects on Surface Electrostatics

Mitochondrial dysfunction includes heritable diseases, acquired pathologies, and age-related declines in health. Szeto-Schiller (SS) peptides comprise a class of amphipathic tetrapeptides that have demonstrated efficacy in treating a wide array of mitochondrial disorders, and are believed to target mitochondrial membranes due to their enrichment in the anionic phospholipid cardiolipin (CL). However, little is known regarding how SS peptides interact with or alter the physical properties of lipid bilayers. In this study, we have analyzed the interactions of the lead compound SS-31 (Elamipretide) with model and mitochondrial membranes using biophysical and computational approaches. Our results show that this polybasic peptide partitions into the membrane interfacial region with affinity and binding density that are directly related to surface charge. SS-31 binding does not destabilize lamellar bilayers even at the highest binding concentrations; however, it does cause saturable alterations in lipid packing. Most notably, SS-31 modulates the surface electrostatic properties of model and mitochondrial membranes, which could play a significant role in the mitoprotective properties of this compound. As a proof of concept, we show that SS-31 alters ion distribution at the membrane interface with implications for maintaining mitochondrial membranes subject to divalent cation (calcium) stress. Taken together, these results support a mechanism of action in which SS peptides interact with lipid bilayers and alter the biophysical (primarily electrostatic) properties of mitochondrial membranes as their primary mechanism of action. Understanding this molecular mechanism is key to the development of future compound variants with enhanced efficacy.\n\nSignificanceSzeto-Schiller (SS) peptides are among the most promising therapeutic compounds for mitochondrial dysfunction. However, the molecular target(s) and the mechanism of action of SS peptides are poorly understood. In this study, we evaluate the interaction of the lead compound SS-31 (Elamipretide) with mitochondrial and synthetic model membranes using a host of biophysical techniques. Our results show that SS-31 membrane interaction is driven largely by the negative surface charge of mitochondrial membranes and that SS-31 alters lipid bilayer properties, most notably electrostatics at the membrane interface. This work supports a mechanism in which SS peptides act on a key physical property of mitochondrial membranes rather than with a specific protein complex, consistent with the exceptionally broad therapeutic efficacy of these compounds.

biophysics↗