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Baniasadi, H.

Publications and source records attributed to Baniasadi, H..

8 recordsLinked to original sources
bioRxiv2025

Mitochondrial membrane junction-mediated ATP channeling drives activity-dependent glucose metabolism

Neurons and brown adipocytes rely on rapid ATP production from accelerated glucose metabolism to sustain bursts of activity upon stimulation, a process known as activity-dependent glucose metabolism. The first committed step in this pathway, the hexokinase I (HK1)-catalyzed phosphorylation of glucose, consumes ATP, raising the question of how this reaction can be accelerated when cytosolic ATP becomes limiting during stimulation. We identify Cell Cycle Exit and Neuronal Differentiation protein 1 (CEND1), expressed in both cell types, as a critical regulator of this process. Loss of CEND1 impairs activity-dependent glucose utilization, ATP generation, and stimulation-evoked activity both in vitro and in vivo. Mechanistically, CEND1 assembles a complex with HK1, voltage-dependent anion channel 1 (VDAC1), and adenine nucleotide translocase 1 (ANT1) at hemifusion-like membrane junction between the outer/inner mitochondrial membrane, channeling mitochondrially derived ATP directly to HK1. These findings uncover a previously unrecognized mechanism that sustains activity-dependent glucose metabolism, with broad implications for energy homeostasis in specialized cell types.

physiology↗
bioRxiv2024

IL-1b-mediated Immunometabolic Adaptation in Corneal Epithelial Cells

PurposeAs an external mucosal surface, the corneal epithelium is subject to a barrage of stressors that are known to trigger inflammation. IL-1{beta}, a master regulator of inflammation, is secreted into the preocular tear film by ocular surface epithelial cells and infiltrating immune cells. While increased levels of IL-1{beta} have been associated with corneal disease, the effects of IL-1{beta} on mitochondrial function in corneal epithelial cells (CECs) is unknown. MethodsTo investigate the effects of IL-1{beta} on mitochondrial function, telomerase immortalized human CECs were cultured in either 50 ng/mL or 100 ng/mL IL-1{beta} for short term (24 hours) or prolonged (72 hours) time periods. Cells were assessed for ROS, inflammatory cytokine production, mitochondrial polarization and ultrastructure, mitophagy, and changes in the metabolite composition. Lipid drops were examined using light and fluorescent microscopy. ResultsShort term exposure to IL-1{beta} triggered an increase in IL-8 and ROS levels that corresponded to a reduction in mitochondrial membrane potential. Long term exposure also showed increased levels of IL-8 and IL-6 and further increased ROS. After long term exposure however, there was a paradoxical increase in mitochondrial membrane potential that was associated an increase in spare respiratory capacity and mitochondrial hyperfusion. Metabolomics confirmed an upregulation of the pentose phosphate pathway and the TCA cycle. Fumarate was also increased, suggesting an increase in flux through complex II. Changes in lipid metabolism included an upregulation in cardiolipin and de novo triacylglyceride biosynthesis, along with increasing numbers of lipid droplets. ConclusionProlonged exposure to IL-1{beta} induces metabolic rewiring in CECs that results in an increase in spare respiratory capacity. These findings suggest that the corneal epithelium is able to adapt to certain levels of chronic inflammation and may have important implications in our understanding of immune tone and cellular stress responses in ocular surface epithelia.

immunology↗
bioRxiv2024

Pseudomonas aeruginosa infection increases palmitoyl carnitine release by host-derived extracellular vesicles

Pseudomonas aeruginosa (PA), an opportunistic gram-negative pathogen, is the most common pathogen identified in all culture positive cases of infectious keratitis. Extracellular vesicles (EVs) are released by most cells in the body and function in intercellular communication. We have previously reported a change in the proteome of host-derived EVs from corneal epithelial cells during PA infection. In the present study, we investigated changes in the metabolome of host-derived EVs from PA infected (PA-C EVs) and non-infected cells (C EVs). We found that one metabolite, palmitoyl carnitine (PAMC), was significantly upregulated in PA-C EVs. To determine the significance of PAMC release, we investigated the effect of PAMC treatment on corneal epithelial cells and neutrophils. EVs were isolated from culture media using size exclusion chromatography. EVs were then characterized using nanoparticle tracking analysis, transmission electron microscopy, and western blot. Metabolomics was performed using an untargeted approach. We found that palmitoyl carnitine (PAMC) was the most abundant metabolite present in PA-C EVs and was increased more than 3 fold compared to C EVs. Treatment of corneal epithelial cells with increasing levels of PAMC increased nuclear translocation of the NF-{kappa}B subunit p65. This was associated with an increase in IL-8 production and neutrophil migration. PAMC also increased levels of mitochondrial calcium. Upon inoculation of corneal epithelial cells with PA, 50 M PAMC completely eradicated intracellular PA, but stimulated growth of extracellular PA. Taken together, these findings suggest that PA exploits EV release by host cells to deplete PAMC from the intracellular environment.

microbiology↗
bioRxiv2024

Pseudomonas aeruginosa impairs mitochondrial function and metabolism during infection of corneal epithelial cells

Pseudomonas aeruginosa (PA) is a gram-negative opportunistic pathogen that can infect the cornea as a result of trauma or contact lens wear. In addition to their known energy producing role, mitochondria are important mediators of immune signaling and host defense. While certain pathogens have developed strategies to evade host defenses by modulating host mitochondrial dynamics and metabolism, the ability of PA to harness host cell mitochondria during corneal infection is unknown. Using a combination of biochemical and imaging techniques, we show that PA infection of corneal epithelial cells induced mitochondrial fission in a DRP1-dependent manner that preceded PINK1/Parkin and FUNDC1-mediated mitophagy. PA also impaired NADH-linked respiration through a reduction in complex 1. This corresponded to a decrease in metabolic pathways related to glycolysis and the TCA cycle. Metabolomics analysis further demonstrated an upregulation of the pentose phosphate pathway, arginine, purine, and pyrimidine metabolism in PA infected cells. These pathways may provide a key source of nucleotides, amino acids, and nitrogen for both the host cell and PA, in addition to antioxidant functions. Following treatment with gentamicin to kill all extracellular bacteria, metabolic flux analysis showed that corneal epithelial cells were able to restore mitochondrial function despite the continued presence of intracellular PA. Taken together, these data demonstrate that mitochondrial dysfunction and metabolic rewiring in host cells is triggered by extracellular PA, but once inside, PA requires healthy mitochondria to ensure host cell survival.

microbiology↗
bioRxiv2022

Small Molecule Properties Define Partitioning into Biomolecular Condensates

Biomolecular condensates regulate cellular function by compartmentalizing molecules without a surrounding membrane1,2. Condensate functions are believed to arise from the specific exclusion or enrichment of molecules3-5. Thus, understanding the principles governing condensate composition is critical to characterizing condensate function. The molecular bases of macromolecular composition have been studied in detail for several condensates6-9, but partitioning of small molecules into condensates remains poorly understood. Using mass spectrometry with validation by fluorescence microscopy, we quantified partitioning of [~]1700 metabolites and FDA-approved drugs into four condensates composed of different DNA and/or protein scaffolds. We found that partitioning spanned from [~]100-fold exclusion to [~]10,000-fold enrichment. Strong correlations between the different condensates suggest an underlying physical similarity despite disparate macromolecular components. Strongly partitioning molecules generally did not bind condensate-forming proteins with high affinity under conditions where condensates do not form, suggesting only a minor role for stereospecific interactions in partitioning. We developed a machine learning model that accurately predicts partitioning using only physicochemical properties of the compounds. The strongest predictors of partitioning were features related to aqueous solubility and hydrophobicity. Small molecule partitioning was similar for condensates in aqueous buffer and in concentrated cell extracts, suggesting analogous behaviors in vivo. Together, the data and model suggest that small molecule partitioning is not generally based on high-affinity, stereospecific interactions with scaffolds, but rather on physical properties of the compounds, and their compatibility with an emergent hydrophobic environment within the condensate. Our results will aid design of chemical compounds that target biomolecular condensates and reveal unexpected physical and functional similarities of distinct condensates.

biochemistry↗
bioRxiv2021

TMEM120 is a coenzyme A-binding membrane protein with structural similarities to ELOVL fatty acid elongase

TMEM120A, also named as TACAN, is a novel membrane protein highly conserved in vertebrates and was recently proposed to be a mechanosensitive channel involved in sensing mechanical pain. Here we present the single particle cryo-EM structure of human TMEM120A which forms a tightly packed dimer with extensive interactions mediate by the N-terminal coiled coil domain (CCD), the C-terminal transmembrane domain (TMD), and the re-entrant loop between the two domains. The TMD of each TMEM120A subunit contains six transmembrane helices (TMs) and has no clear structural feature of a channel protein. Instead, the six TMs form an -barrel with a deep pocket where a coenzyme A (CoA) molecule is bound. Intriguingly, some structural features of TMEM120A resemble those of elongase for very long-chain fatty acid (ELOVL) despite low sequence homology between them, pointing to the possibility that TEME120A may function as an enzyme for fatty acid metabolism, rather than a mechanosensitive channel.

biophysics↗
bioRxiv2019

The Lon protease links nucleotide metabolism with proteotoxic stress

During stress all cells must maintain proteome quality while sustaining critical processes like DNA replication. In bacteria, the Lon protease is the central route for degradation of misfolded proteins. Here, we show that in Caulobacter crescentus Lon controls dNTP pools during stress through degradation of the transcription factor CcrM. We find that elevated dNTP/NTP ratios in {Delta}lon cells protects them from deletion of otherwise essential dTTP-producing pathways and shields them from lethality of hydroxyurea, known to catastrophically deplete dNTPs. Increased dNTP production in {Delta}lon results from higher expression of ribonucleotide reductase driven by increased CcrM. We show that misfolded proteins can stabilize CcrM by competing for limiting protease and Lon-dependent control of dNTPs improves fitness during protein misfolding conditions. We propose that linking dNTP production with the availability of Lon allows Caulobacter to maintain replication capacity when misfolded protein burden increases, such as during rapid growth or unanticipated proteotoxic stress. HighlightsO_LIdCTP deaminase (DCD) is dispensable when Lon protease is absent due to increased dNTP pools. C_LIO_LIStabilization of the Lon substrate CcrM transcriptionally upregulates ribonucleotide reductase, affording protection against hydroxyurea. C_LIO_LIMisfolded proteins can competitively inhibit CcrM degradation by the Lon protease. C_LIO_LITitration of protein quality control is a mechanism that allows cells to respond to stresses that lack dedicated signal response pathways. C_LI

microbiology↗