Membrane currents and pacemaking in corticotrophs and hiPSC-derived dopaminergic neurons

Many neural networks are required to function at particular frequencies. These processes are often driven by rhythmic, intrinsically generated electrical activity that is produced by cells described as pacemaker neurons. Two disease-relevant in-vitro models were investigated that display poorly understood pacemaker activity; AtT20 anterior pituitary corticotrophs and human induced pluripotent stem cell (hiPSC)-derived dopaminergic (DA) neurons. Using electrophysiology and Ca2+ imaging, gaps in our understanding of pacemaking in these cell types were investigated. For AtT20s, it was revealed that hormone secretion in this cell type is uncoupled from its electrical activity. Novel roles were found for T-type voltage-gated calcium channels (VGCCs) in pacemaking and for L-type VGCCs in maintaining intracellular Ca2+ concentrations. hiPSC-derived DA neurons were found to produce apparently spontaneous electrical activity in culture that was dependent upon L-type VGCCs. This pacemaking was not found to be intrinsic, instead being driven by and developing in parallel with synaptic input in culture. These DA neurons immunostained for the L-type VGCC subtype CaV1.3, which is involved in the death of DA neurons in Parkinson's disease. Using a novel cell death assay these neurons were found to be selectively susceptible to the DA toxin 6-hydroxydopamine but displayed a resistance to glutamate-induced excitotoxicity. Data here provides valuable information on the similarities and differences between these in-vitro models and their in-vivo counterparts. This allowed for an in-depth assessment of their suitability as models for their respective diseases, hopefully leading to the targeted, efficient design of studies that use these cell types

Molecular simulation of partially denatured β-lactoglobulin

From Elsevier via Jisc Publications RouterHistory: accepted 2023-04-22, issued 2023-04-29Article version: AMPublication status: AcceptedFunder: Heriot-Watt University; FundRef: https://doi.org/10.13039/100009767Funder: Engineering & Physical Sciences Research Council; Grant(s): EP/J501682/1Julien Lonchamp - ORCID: 0000-0001-7954-4745 https://orcid.org/0000-0001-7954-4745The unfolding of β-lactoglobulin (β-lac) upon heating was comprehensively studied through molecular dynamics computer simulations. A β-lac molecule in the aqueous solution was firstly heated at 500 K for unfolding and then annealed at 300 K to collect stable conformations. There were five meta-stable conformations observed based on the Free Energy Landscape (FEL). The β-lac molecule was found to exhibit an open and extended conformation on heating followed by limited refolding upon cooling. The cysteine residues –SH121 and S–S66-160 in the most open conformation were located at the opposite ends of the β-lac molecule. This would favour the intermolecular –SH/S–S interchange reactions that are known to occur in β-lac as part of the inter-molecular aggregation process. Furthermore, the unfolding of the β-lac increased the hydrogen bond forming capacity between water molecules and the protein and between water molecules themselves. The interactions and the properties of the water molecules in the protein hydration shell also indicated that the hydration shell was stabilized by protein unfolding. However, it was found that the unfolding of β-lac increased diffusion of hydration water molecules, including those in the first hydration shell that interact more strongly with the protein. This may partly explain why unfolded proteins are more likely to aggregate even though there were more hydration water molecules protecting them. Such results provided more detailed information on the structure-functionality relationship of β-lac based on both the protein molecule and its hydration shell. This provides insight into how we can control the processing of proteins for desirable functional properties such as thickening and gelation, which are modified through protein-water interactions.inpressinpres

Stable emulsions of droplets in a solid edible organogel matrix

Sitosterol–oryzanol organogels are unstable near water, but are shown to be stable in the presence of glycerol.</p