Biology subjects

Pavlov, E. V.

Publications and source records attributed to Pavlov, E. V..

5 recordsLinked to original sources

bioRxiv2025

Effects of Natural Lithium and Lithium Isotopes on Voltage Gated Sodium Channel Activity in SH-SY5Y and IPSC Derived Cortical Neurons

Although lithium (Li) is a widely used treatment for bipolar disorder, its exact mechanisms of action remain elusive. Research has shown that the two stable Li isotopes, which differ in their mass and nuclear spin, can induce distinct effects in both in vivo and in vitro studies. Since sodium (Na+) channels are the primary pathway for Li+ entry into cells, we examined how Li+ affects the current of Na+ channels using whole-cell patch-clamp techniques on SH-SY5Y neuroblastoma cells and human iPSC-derived cortical neurons. Our findings indicate that mammalian Na+ channels in both neuronal models studied here display no selectivity between Na+ and Li+, unlike previously reported bacterial Na+ channels. We observed differences between the two neuronal models in three measured parameters (Vhalf, Gmax,z). We saw no statistically significant differences between any ions in SHSY-5Y cells, but small differences in the half-maximum activation potential (Vhalf) between Na+ and 6Li+ and between 7Li+ and 6Li+ were found in iPSC-derived cortical neurons. Although Na+ channels are widely expressed and important in neuronal function, the very small differences observed in this work suggest that Li+ regulation through Na+ channels is likely not the primary mechanism underlying Li+ isotope differentiation.

neuroscience↗

bioRxiv2021

Holographic imaging of mitochondrial optical density in living cells reveals that the Mitochondrial Permeability Transition is a two-stage process

A sudden increase in permeability of the mitochondrial inner membrane, mitochondrial permeability transition (PT), is the central event responsible for cell death and tissue damage in conditions such as stroke and heart attack. PT is caused by the opening of the Cyclosporin A (CSA) dependent calcium-induced pore, the Permeability Transition Pore (PTP). The molecular details of PTP are incompletely understood. We utilized a combination of holographic and fluorescent microscopy to assess the contribution of the ATP synthase and Adenine Nucleotide Translocator (ANT) towards PTP. In cells lacking either ATP synthase or ANT, we observed CSA-sensitive membrane depolarization, but not high-conductance PTP. Further, we found that in wild-type cells calcium induced CSA-sensitive depolarization precedes opening of the PTP, which occurred until after nearly complete mitochondrial membrane depolarization. We propose that both ATP synthase and ANT are required for high conductance PTP but not depolarization, which presumably occurs through activation of the low conductance PT, which has a molecular nature that is different from both complexes.

cell biology↗

bioRxiv2020

The Mitochondrial Permeability Transition Phenomenon Elucidated by Cryo-EM Reveals the Genuine Impact of Calcium Overload on Mitochondrial Structure and Function

Mitochondria have a remarkable ability to uptake and store massive amounts of calcium. However, the consequences of massive calcium accumulation remain enigmatic. In the present study, we analyzed a series of time-course experiments to identify the sequence of events that occur in a population of guinea pig cardiac mitochondria exposed to excessive calcium overload that cause mitochondrial permeability transition (MPT). By analyzing coincident structural and functional data, we determined that excessive calcium overload is associated with large calcium phosphate granules and inner membrane fragmentation, which explains the extent of mitochondrial dysfunction. This data also reveals a novel mechanism for cyclosporin A, an inhibitor of MPT, in which it preserves inner membrane architecture despite the presence of massive calcium phosphate granules in the matrix. Overall, these findings establish a mechanism of calcium-induced mitochondrial dysfunction and the impact of calcium regulation on mitochondrial structure and function.

cell biology↗

bioRxiv2020

C subunit of the ATP synthase is an amyloidogenic channel-forming peptide: possible implications in mitochondrial pathogenesis

The c subunit is an inner mitochondrial membrane (IMM) protein and is an integral part of the F0 complex of the ATP synthase. Under physiological conditions, this short 75 residue-long peptide folds into an -helical hairpin and forms oligomers spanning the lipid bilayer. In addition to its physiological role, the c subunit has been proposed as a key participant in stress-induced IMM permeabilization by the mechanism of calcium-induced permeability transition. However, the molecular mechanism of the c subunit participation in IMM permeabilization is not completely understood. Here we used fluorescence spectroscopy, atomic force microscopy and black lipid membrane methods to gain insights into the structural and functional properties of c subunit protein that make it relevant to mitochondrial toxicity. We discovered that c subunit is an amyloidogenic peptide that can spontaneously fold into {beta}-sheets and self-assemble into fibrils and oligomers. C subunit oligomers exhibited ion channel activity in lipid membranes. We propose that the toxic effects of c subunit might be linked to its amyloidogenic properties and are driven by mechanisms similar to those of neurodegenerative polypeptides such as A{beta} and -synuclein.

biophysics↗

bioRxiv2018

Inorganic polyphosphate (polyP) is required for sustained free mitochondrial calcium elevation, following stimulated calcium uptake.

Mitochondrial free calcium is critically linked to the regulation of bioenergetics and cellular signaling. Free calcium concentrations within the organelle are regulated by two processes: flux across the mitochondrial inner membranes and buffering by phosphate. The key role of phosphate in the buffering of free calcium in mitochondria is well-established. Specifically, during stimulated calcium uptake, calcium is partially buffered by orthophosphate, allowing for elevated calcium concentrations, while preventing calcium toxicity. However, this buffering system is expected to lead to the irreversible formation of insoluble precipitates, which are not observed in living cells, under physiological conditions. Here, we demonstrate that the regulation of free mitochondrial calcium requires the presence of free inorganic polyphosphate (polyP) within the organelle. Specifically, we found that the overexpression of a mitochondrial-targeted enzyme hydrolyzing polyP, leads to the loss of the cellular ability to maintain elevated calcium concentrations within the organelle, following stimulated cytoplasmic signal. We hypothesize that the presence of polyP prevents the formation of calcium-phosphate insoluble clusters, allowing for the maintenance of elevated free calcium levels, during stimulated calcium uptake.

molecular biology↗