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Examining the Effect of Charged Lipids on Mitochondrial Outer Membrane Dynamics Using Atomistic Simulations
Aline A Oliveira1,2, Tomasz Róg3, Albérico B F da Silva2
1Department of Chemistry and Biochemistry, University of California San Diego, San Diego, CA 92093-0340, USA.
Abstract:
The outer mitochondrial membrane (OMM) is involved in multiple cellular functions such as apoptosis, inflammation and signaling via its membrane-associated and -embedded proteins. Despite the central role of the OMM in these vital phenomena, the structure and dynamics of the membrane have regularly been investigated in silico using simple two-component models. Accordingly, the aim was to generate the realistic multi-component model of the OMM and inspect its properties using atomistic molecular dynamics (MD) simulations. All major lipid components, phosphatidylinositol (PI), phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS), were included in the probed OMM models. Because increased levels of anionic PS lipids have potential effects on schizophrenia and, more specifically, on monoamine oxidase B enzyme activity, the effect of varying the PS concentration was explored. The MD simulations indicate that the complex membrane lipid composition (MLC) behavior is notably different from the two-component PC-PE model. The MLC changes caused relatively minor effects on the membrane structural properties such as membrane thickness or area per lipid; however, notable effects could be seen with the dynamical parameters at the water-membrane interface. Increase of PS levels appears to slow down lateral diffusion of all lipids and, in general, the presence of anionic lipids reduced hydration and slowed down the PE headgroup rotation. In addition, sodium ions could neutralize the membrane surface, when PI was the main anionic component; however, a similar effect was not seen for high PS levels. Based on these results, it is advisable for future studies on the OMM and its protein or ligand partners, especially when wanting to replicate the correct properties on the water-membrane interface, to use models that are sufficiently complex, containing anionic lipid types, PI in particular.
Insights
Realistic outer mitochondrial membrane models reveal complex lipid behavior. Varying anionic lipid levels, particularly phosphatidylserine, impact membrane dynamics and hydration at the water-interface, crucial for future studies.
Area of Science:
- Biochemistry
- Computational Biology
- Membrane Biophysics
Background:
- The outer mitochondrial membrane (OMM) plays a critical role in cellular processes like apoptosis and signaling.
- Current in silico models of the OMM often use simplified two-component systems, potentially missing crucial complexities.
- Understanding OMM structure and dynamics is vital for deciphering its role in cellular functions.
Purpose of the Study:
- To develop a realistic multi-component model of the outer mitochondrial membrane (OMM).
- To investigate the properties of this complex model using atomistic molecular dynamics (MD) simulations.
- To explore the impact of varying anionic lipid concentrations, specifically phosphatidylserine (PS), on OMM behavior.
Main Methods:
- Construction of multi-component models of the OMM including phosphatidylinositol (PI), phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS).
- Atomistic molecular dynamics (MD) simulations to analyze membrane structural and dynamical properties.
- Systematic variation of phosphatidylserine (PS) lipid concentration to assess its effects.
Main Results:
- Multi-component lipid composition (MLC) models exhibit distinct behavior compared to simple PC-PE models.
- Changes in MLC had minor effects on structural properties but significant impacts on water-membrane interface dynamics.
- Increased PS levels slowed lipid lateral diffusion; anionic lipids generally reduced hydration and PE headgroup rotation.
- Sodium ion neutralization of the surface was observed with PI but not with high PS levels.
Conclusions:
- Complex, multi-component OMM models are necessary for accurately simulating membrane properties, especially at the water-membrane interface.
- Anionic lipid content, particularly PI, significantly influences OMM dynamics and ion interactions.
- Future research on OMM proteins and ligands should utilize detailed models incorporating anionic lipids for greater fidelity.
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