Biology subjects

Galkin, A.

Publications and source records attributed to Galkin, A..

7 recordsLinked to original sources

bioRxiv2026

Lipid mediated ER-stress contributes to the pathogenesis of mitochondrial myopathies

Mitochondrial diseases are a heterogeneous group of genetic disorders caused by impaired oxidative phosphorylation (OxPhos). When skeletal muscle is predominantly affected, they are defined as primary mitochondrial myopathies. Although the genetic causes of mitochondrial myopathies and the resulting bioenergetic impairments are well established, the metabolic drivers behind progressive muscle dysfunction remain poorly defined. This gap in knowledge may contribute to the lack of effective treatments for these disorders. OxPhos defective muscle initiates a metabolic response coordinated by systemic signals which invokes the mobilization of fatty acids from white adipose tissue despite muscle inability to fully oxidize fatty acids due to OxPhos impairment. Here, we show that in human patients with mitochondrial disease and mice with OxPhos defective muscle, increased fatty acid mobilization from white adipose tissue leads to ectopic lipid accumulation and lipotoxicity in skeletal muscle. We find an increase in very long chain ceramides which are mechanistically linked to chronic ER stress, phosphorylation of eIF2, and activation of ATF4 signaling. We propose that Ph-eIF2-mediated attenuation of global protein synthesis and ATF4-initiated atrophy pathways contribute to muscle wasting and weakness. Importantly, inhibition of de novo synthesis of ceramides with myriocin reduces ER stress and improves muscle proteostasis, body weight, and motor functions in a conditional COX10 KO mouse model of mitochondrial myopathy. Together, these findings highlight altered lipid metabolism as a contributor of mitochondrial myopathy pathogenesis and identify lipid-mediated stress pathways that can be targeted therapeutically.

Molecular Biology↗

bioRxiv2026

Discovery and Preclinical Validation of a Clinically Optimized Mitochondrial Complex I Modulator for Alzheimer's Disease

Alzheimers disease (AD) is characterized by diminished capacity to mount adaptive cellular stress responses required to maintain energy homeostasis and proteostasis. An emerging therapeutic strategy is to restore adaptive stress responses by inducing mild energetic stress through inhibition of mitochondrial complex I (mtCI). However, pharmacological inhibition of the respiratory chain has remained challenging, as it can induce bioenergetic failure rather than beneficial signaling. Here, we describe C273, a brain-penetrant small molecule that delivers controlled, weak attenuation of mtCI activity to therapeutically restore endogenous adaptive stress pathways. This work establishes a first-in-class mechanism in which calibrated activation of multifaceted adaptive mechanisms enhances cellular resilience, rather than impairing mitochondrial function. Structure-activity relationship optimization yielded a compound with high potency against A{beta}-induced cellular toxicity, strong selectivity for mtCI, and favorable drug-like properties. C273 demonstrated excellent oral bioavailability, metabolic stability in mouse, rat, and human microsomes, minimal CYP liabilities, and a clean ancillary pharmacology profile in the Eurofins CEREP44 panel. In vivo, C273 readily crosses the blood-brain barrier and activates AMP-activated protein kinase (AMPK), initiating a coordinated hormetic response characterized by enhanced antioxidant defenses, suppression of inflammatory signaling, induction of autophagy, and increased mitochondrial biogenesis and turnover. Genetic deletion of AMPK1/2 abolished these responses, establishing AMPK as a critical mediator of C273 activity. Pharmacological competition experiments further confirmed the target, as pretreatment with non-toxic concentrations of rotenone blocked C273 interaction with the quinone-binding site of mtCI and eliminated its neuroprotective effects. Repeated oral administration of C273 (20-80 mg/kg/day) to wild-type mice for one month produced no detectable cardiac or hepatic toxicity, indicating a favorable in vivo safety margin. Importantly, C273 activated these mechanisms and reduced A{beta} and p-Tau levels in induced pluripotent stem cell-derived cerebral organoids from patients with sporadic AD. Collectively, these results establish controlled mtCI modulation as a therapeutic strategy and position C273 as a promising disease-modifying candidate for AD.

neuroscience↗

bioRxiv2025

Leveraging BRG1 Driven Ferroptosis Resistance to Overcome Treatment Resistance

Resistance to Brutons tyrosine kinase inhibitors (BTKi) remains a major therapeutic challenge in B-cell malignancies, limiting treatment durability. Here, we identify ferroptosis suppression as a central mechanism of BTKi resistance in mantle cell lymphoma (MCL). Aberrant BRG1 activity protects cells from BTKi-induced ferroptosis by restricting reactive oxygen species (ROS) and labile iron. Mechanistically, BRG1 promotes resistance through both BTK-dependent survival signaling and a BTK-independent transcriptional program. The latter is mediated by BRG1-driven induction of MEF2B, which upregulates NDUFA4L2 to inhibit mitochondrial respiration, thereby blocking mitochondria-dependent ferroptosis. Pharmacologic inhibition of BRG1 disrupts these programs, restoring ferroptotic sensitivity and synergizing with BTKi across resistant MCL models. Together, these findings establish BRG1 as a central regulator of therapy resistance and provide a rationale for co-targeting BRG1 and BTK as a therapeutic strategy for B-cell malignancies.

cancer biology↗

bioRxiv2025

Rescuing Ischemic Brain Injury by Rewiring Mitochondrial Electron Flow

Mitochondrial metabolic flux alterations are critical drivers of acute ischemia-reperfusion (IR) brain injury. Reverse electron transfer (RET), defined as the upstream flow of electrons from the quinone pool to complex I, is a major source of pathological reactive oxygen species (ROS) under stress conditions. In an in vivo brain IR model, oxygen deprivation induces the buildup of RET-supporting substrates, with glycerol 3-phosphate identified as the dominant contributor in addition to succinate. Rapid oxidation of these substrates by brain mitochondria upon reoxygenation drives massive ROS production, while also leading to over-reduction and dissociation of the complex I flavin mononucleotide (FMN) cofactor. The resulting FMN-deficient complex I becomes catalytically impaired, unable to oxidize NADH or to produce ROS. To mitigate RET and preserve complex I function, we used transgenic mice xenotopically expressing alternative oxidase (AOX). This enzyme bypasses complexes III and IV by directly oxidizing the reduced quinone pool and passing electrons onto molecular oxygen. AOX expression did not alter complex I abundance, supercomplexes assembly, or basal respiration rates, but effectively diverted electrons from the quinone pool, decreasing RET flux via complex I and limiting ROS generation during IR. For the first time we showed that AOX expression and attenuation of RET preserved complex I FMN binding, suppressed oxidative stress, and conferred neuroprotection in vivo. Our findings reveal a novel strategy for rewiring mitochondrial electron flux to mitigate initial IR brain injury, highlighting modulation of the quinone pool by AOX as a potential therapeutic strategy for IR.

biochemistry↗

bioRxiv2022

Altered MAM function shifts mitochondrial metabolism in SOD1-mutant models of ALS

Mitochondrial defects are a common hallmark of familial and sporadic forms of amyotrophic lateral sclerosis (ALS). However, the origin of these defects, including reduced pyruvate metabolism and reduced oxygen consumption, is poorly understood. These metabolic functions are regulated in specialized endoplasmic reticulum (ER) domains in close contact with mitochondria, called mitochondrial-associated ER membranes (MAM). Recently it has been shown that MAM domains are disrupted in ALS, but the connection between MAM dysregulation and mitochondrial defects in ALS cells remains unclear. Using human embryonic stem cell (ESC)-derived motor neurons (hMNs) and mouse models with ALS-pathogenic mutations in superoxide dismutase 1 (SOD1), we found that the glycolytic deficiency in ALS is a direct consequence of the progressive disruption of MAM structure and function that hinders the use of glucose-derived pyruvate as a mitochondrial fuel and triggers a shift in mitochondrial substrates from pyruvate to fatty acids. This glycolytic deficiency, over time, induces significant alterations in mitochondrial electron flow and in the active/dormant (A/D) status of complex I in spinal cord, but not in brain. These data agree with a role for MAM in the maintenance and regulation of cellular glucose metabolism and suggest that MAM disruption in ALS could be the underlying cause of the bioenergetic deficits observed in the disease.

molecular biology↗

bioRxiv2020

Partial inhibition of mitochondrial complex I attenuates neurodegeneration and restores energy homeostasis and synaptic function in a symptomatic Alzheimers mouse model

We demonstrate that mitochondrial respiratory chain complex I is an important small molecule druggable target in Alzheimers Disease (AD). Partial inhibition of complex I triggers the AMP-activated protein kinase-dependent signaling network leading to neuroprotection in symptomatic APP/PS1 mice, a translational model of AD. Treatment of APP/PS1 mice with complex I inhibitor after the onset of AD-like neuropathology improved energy homeostasis, synaptic activity, long-term potentiation, dendritic spine maturation, cognitive function and proteostasis, and reduced oxidative stress and inflammation in brain and periphery, ultimately blocking the ongoing neurodegeneration. Therapeutic efficacy in vivo was monitored using translational biomarkers FDG-PET, 31P NMR, and metabolomics. Cross-validation of the mouse and the human AMP-AD transcriptomic data demonstrated that pathways improved by the treatment in APP/PS1 mice, including the immune system response and neurotransmission, represent mechanisms essential for therapeutic efficacy in AD patients.

neuroscience↗

bioRxiv2019

Amyloid conformers of the FXR1 protein prevent mRNA degradation in cortical neurons

Functional amyloids regulate vital processes in a variety of organisms from bacteria to higher eukaryotes. The development of methods enabling large-scale screening for amyloids opens up opportunity for systemic analysis of the prevalence of amyloids in nature. Using an original proteomic approach, we identified several proteins forming amyloid-like detergent-resistant aggregates in the rat brain. One of them is the FXR1 protein, which is known to regulate memory and emotions (1, 2). We demonstrated that in brain FXR1 forms amyloid oligomers and insoluble detergent-resistant aggregates that strongly colocalize with amyloid-specific dye Thioflavin S and bind mRNA molecules. Moreover, we demonstrated that mRNAs colocalized with FXR1 amyloid particles are completely resistant to treatment with RNAse A. Taking into consideration that the members of ribonuclease A superfamily function in neurons (3) we can conclude that amyloid conformers of FXR1 control RNA stability in brain. Thus, in contrast to pathological amyloids that cause neurodegeneration, FXR1 is the functional amyloid in forebrain. We showed that amyloid properties of FXR1 depend on its N-terminal part from 1 to 379 amino acids. This fragment forms amyloid fibrils in vitro that bind Congo red and manifest apple-green birefringence when assayed by polarization microscopy. The amyloid-forming region of FXR1 is highly conserved in mammals. These data suggest that the ability of amyloid conformers of FXR1 to protect mRNAs is characteristic of different mammalian species, including humans. Significance StatementAmyloids are highly ordered cross-{beta} sheet protein fibrils associated with many neurodegenerative diseases including Alzheimers disease. However, some amyloid proteins regulate vital processes. We identified a set of proteins that form amyloid-like aggregates in the brain of healthy rats. One of them - the FXR1 protein is known to regulate memory and emotions. FXR1 forms amyloid fibrils that bind RNA molecules and prevent their degradation in brain cortex neurons. Amyloid-forming sequence of FXR1 is highly conserved across mammals including human. Discovery of functional amyloids in mammalian brain shows that strategy aimed at the development of universal anti-amyloid drugs is unpromising. Such potential drugs should prevent or suppress formation of pathological aggregates of a certain protein, but not affect functional amyloids.

neuroscience↗