Biology subjects

Rems, L.

Publications and source records attributed to Rems, L..

5 recordsLinked to original sources

bioRxiv2025

Acetaminophen attenuates pathological pain through a mechanism that requires CB1 cannabinoid receptors and the enzyme diacylglycerol lipase in mice

Acetaminophen (APAP) produces analgesia through mechanisms that remain poorly understood. Here, we tested the hypothesis that APAP-induced suppression of pathological pain is associated with cannabinoid receptors and activity of enzymes regulating endogenous lipids (diacylglycerol lipase, DAGL; monoacylglycerol lipase, MAGL) including endocannabinoids. APAP suppressed mechanical hypersensitivity in mouse models of post-surgical and inflammatory pain and the DAGL inhibitors (RHC-80267, DO34) and MAGL inhibitor JZL184 blocked APAPs analgesic effects. Global (rimonabant, AM251) but not peripherally restricted (AM6545) cannabinoid receptor antagonists prevented APAP-induced analgesia. APAP increased corticosterone levels >2-fold and reduced prostaglandins >5-fold across the brain and in the paw skin. In addition, APAP reduced up to 39% of signaling lipids detected in the targeted screen in CFA-treated subjects in a tissue-dependent manner. These observations suggest that APAP plays a wider role in endogenous lipid signaling than previously hypothesized and provides novel insight into mechanisms of action.

neuroscience↗

bioRxiv2024

Structural diversity of Arc oligomers within the excitatory synapse

The Activity-Regulated Cytoskeleton-Associated protein (Arc), is pivotal to mediate plasticity responses in neuronal cells. In vitro studies suggest its ability to form high- and low-order oligomers, which are involved in neuronal trafficking. Despite its important functions, no direct observation of Arc oligomers in cells has been presented due to its highly regulated spatiotemporal expression, the small size of the structures, the lack of appropriate labelling strategies and the background associated to free diffusing cytosolic proteins. Here, we apply super resolution microscopy to observe Arc oligomeric states in cellular environment with focus on the excitatory synapse. In cells, we provide the first evidence of Arc high-order oligomers; we uncovered intermolecular interactions of Arc, its tendency to form liquid condensates and interaction with lipid bilayers. Arc high-order oligomers affect AMPA receptor surface levels. Together, our observations suggest a model by which Arc oligomerization mediates plasma membrane negative curvature favoring AMPA receptors endocytosis.

neuroscience↗

bioRxiv2021

Identification of electroporation sites in the complex lipid organization of the plasma membrane

The plasma membrane of a biological cell is a complex assembly of lipids and membrane proteins, which tightly regulate transmembrane transport. When a cell is exposed to a strong electric field, the membrane integrity becomes transiently disrupted by formation of transmembrane pores. This phenomenon, termed electroporation, is already utilized in many rapidly developing applications in medicine including gene therapy, cancer treatment, and treatment of cardiac arrythmias. However, the molecular mechanisms of electroporation are not yet sufficiently well understood; in particular, it is unclear where exactly pores form in the complex organization of the plasma membrane. In this study we combine coarse-grained molecular dynamics simulations, machine learning methods, and Bayesian survival analysis to identify how formation of pores depends on the local lipid organization. We show that pores do not form homogeneously across the membrane, but colocalize with domains that have specific features, the most important being high density of polyunsaturated lipids. We further show that knowing the lipid organization is sufficient to reliably predict poration sites with machine learning. However, by analysing poration kinetics with Bayesian survival analysis we then show that poration does not depend solely on local lipid arrangement, but also on membrane mechanical properties and the polarity of the electric field. Finally, we discuss how the combination of atomistic and coarse-grained molecular dynamics simulations, machine learning methods, and Bayesian survival analysis can guide the design of future experiments and help us to develop an accurate description of plasma membrane electroporation on the whole-cell level. Achieving this will allow us to shift the optimization of electroporation applications from blind trial-and-error approaches to mechanistic-driven design.

biophysics↗

bioRxiv2019

Pulsed electric fields create pores in the voltage sensors of voltage-gated ion channels

Pulsed electric fields are increasingly used in medicine to transiently increase the cell membrane permeability via electroporation, in order to deliver therapeutic molecules into the cell. One type of events that contributes to this increase in membrane permeability is the formation of pores in the membrane lipid bilayer. However, electrophysiological measurements suggest that membrane proteins are affected as well, particularly voltage-gated ion channels (VGICs). The molecular mechanisms by which the electric field could affects these molecules remain unidentified. In this study we used molecular dynamics (MD) simulations to unravel the molecular events that take place in different VGICs when exposing them to electric fields mimicking electroporation conditions. We show that electric fields induce pores in the voltage-sensor domains (VSDs) of different VGICs, and that these pores form more easily in some channels than in others. We demonstrate that poration is more likely in VSDs that are more hydrated and are electrostatically more favorable for the entry of ions. We further show that pores in VSDs can expand into so-called complex pores, which become stabilized by lipid head-groups. Our results suggest that such complex pores are considerably more stable than conventional lipid pores and their formation can lead to severe unfolding of VSDs from the channel. We anticipate that such VSDs become dysfunctional and unable to respond to changes in transmembrane voltage, which is in agreement with previous electrophyiological measurements showing a decrease in the voltage-dependent transmembrane ionic currents following pulse treatment. Finally, we discuss the possibility of activation of VGICs by submicrosecond-duration pulses. Overall our study reveals a new mechanism of electroporation through membranes containing voltage-gated ion channels. Statement of SignificancePulsed electric fields are often used for treatment of excitable cells, e.g., for gene delivery into skeletal muscles, ablation of the heart muscle or brain tumors. Voltage-gated ion channels (VGICs) underlie generation and propagation of action potentials in these cells, and consequently are essential for their proper function. Our study reveals the molecular mechanisms by which pulsed electric fields directly affect VGICs and addresses questions that have been previously opened by electrophysiologists. We analyze VGICs characteristics, which make them prone for electroporation, including hydration and electrostatic properties. This analysis is easily transferable to other membrane proteins thus opening directions for future investigations. Finally, we propose a mechanism for long-lived membrane permeability following pulse treatment, which to date remains poorly understood.

biophysics↗

bioRxiv2018

Unravelling the response of the actin cortex to electric pulses in vesicles

We study the role of a biomimetic actin cortex during the application of electric pulses that induce electroporation or electropermeabilization, using giant unilamellar vesicles (GUVs) as a model system. The actin cortex, a subjacently attached interconnected network of actin filaments, regulates the shape and mechanical properties of the plasma membrane of mammalian cells, and is a major factor influencing the mechanical response of the cell to external physical cues. We demonstrate that the presence of an actin shell inhibits the formation of macropores in the electroporated GUVs. Additionally, experiments on the uptake of dye molecules after electroporation show that the actin network slows down the resealing process of the permeabilized membrane. We further analyze the stability of the actin network inside the GUVs exposed to high electric pulses. We find disruption of the actin layer that is likely due to the electrophoretic forces acting on the actin filaments during the permeabilization of the GUVs. Our findings on the GUVs containing a biomimetic cortex provide a step towards understanding the discrepancies between the electroporation mechanism of a living cell and its simplified model of the empty GUV.

biophysics↗