Elucidating Daptomycin's Antibacterial Efficacy: Insights into the Tripartite Complex with Lipid II and Phospholipids in Bacterial Septum Membrane.

This study elucidated the mechanism of formation of a tripartite complex containing daptomycin (Dap), lipid II, and phospholipid phosphatidylglycerol in the bacterial septum membrane, which was previously reported as the cause of the antibacterial action of Dap against gram-positive bacteria via molecular dynamics and enhanced sampling methods. Others have suggested that this transient complex ushers in the inhibition of cell wall synthesis by obstructing the downstream polymerization and cross-linking processes involving lipid II, which is absent in the presence of cardiolipin lipid in the membrane. In this work, we observed that the complex was stabilized by Ca2+-mediated electrostatic interactions between Dap and lipid head groups, hydrophobic interaction, hydrogen bonds, and salt bridges between the lipopeptide and lipids and was associated with Dap concentration-dependent membrane depolarization, thinning of the bilayer, and increased lipid tail disorder. Residues Orn6 and Kyn13, along with the DXDG motif, made simultaneous contact with constituent lipids, hence playing a crucial role in the formation of the complex. Incorporating cardiolipin into the membrane model led to its competitively displacing lipid II away from the Dap, reducing the lifetime of the complex and the nonexistence of lipid tail disorder and membrane depolarization. No evidence of water permeation inside the membrane hydrophobic interior was noted in all of the systems studied. Additionally, it was shown that using hydrophobic contacts between Dap and lipids as collective variables for enhanced sampling gave rise to a free energy barrier for the translocation of the lipopeptide. A better understanding of Dap's antibacterial mechanism, as studied through this work, will help develop lipopeptide-based antibiotics for rising Dap-resistant bacteria.

The Role of Cardiolipin in Mitochondrial Function and Neurodegenerative Diseases.

Cardiolipin (CL) is a mitochondria-exclusive phospholipid synthesized in the inner mitochondrial membrane. CL plays a key role in mitochondrial membranes, impacting a plethora of functions this organelle performs. Consequently, it is conceivable that abnormalities in the CL content, composition, and level of oxidation may negatively impact mitochondrial function and dynamics, with important implications in a variety of diseases. This review concentrates on papers published in recent years, combined with basic and underexplored research in CL. We capture new findings on its biological functions in the mitochondria, as well as its association with neurodegenerative diseases such as Alzheimer's disease or Parkinson's disease. Lastly, we explore the potential applications of CL as a biomarker and pharmacological target to mitigate mitochondrial dysfunction.

Falsiroseomonas oryziterrae sp. nov., and Falsiroseomonas oryzae sp. nov., isolated from rice paddy soil.

Three Gram-stain-negative, aerobic, non-motile and coccobacilli-shaped bacterial strains, designated as NPKOSM-4T, NPKOSM-8 and MO-31T, were isolated from rice paddy soil. They had 96.5-100 % 16S rRNA gene sequence similarity to each other, and strains NPKOSM-4T and NPKOSM-8 showed 100 % 16S rRNA gene sequence similarity, confirming that they were the same species. Comparative analysis of 16S rRNA genes with closely related type strains showed that three isolates were most closely related to Falsiroseomonas terricola EM0302T (96.1-97.8 %), Falsiroseomonas wooponensis WW53T (95.51-96.3 %) and Falsiroseomonas bella CQN31T (96.0-96.5 %), respectively. The genomes of strains NPKOSM-4T and MO-31T consisted of 4 632 875 and 6 455 771 bps, respectively, with 72.0 and 72.1 mol% G+C content. The average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridization (dDDH) values between strains NPKOSM-4T and MO-31T and type strains of Falsiroseomonas species were lower than the cut-offs (≥95 % for ANI, ≥95-96 % for AAI and ≥ 70 % for dDDH) required to define a bacterial species. The major fatty acids of strains NPKOSM-4T, NPKOSM-8 and MO-31T were C18 : 1 ω7c and C18 : 1 2-OH (<10 %) and the predominant quinone was Q-10. The polar lipids of strain NPKOSM-4T were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, one unidentified aminophospholipid and three unidentified aminolipids. The polar lipid profiles of strain MO-31T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, one unidentified aminolipid and three unidentified lipids. Based on their distinctive phenotypic, phylogenetic, and chemotaxonomic characteristics, strains NPKOSM-4T, NPKOSM-8 and MO-31T are considered to represent two novel species of the genus Falsiroseomonas, for which the names Falsiroseomonas oryziterrae sp. nov. [to accommodate strains NPKOSM-4T (= KACC 22135T=JCM 34745T), NPKOSM-8 (=KACC 22134=JCM 34746)] and Falsiroseomonas oryzae sp. nov. [to accommodate strain MO-31T (= KACC 22465T=JCM 35532T)] are proposed.

SIRT3 regulates cardiolipin biosynthesis in pressure overload-induced cardiac remodeling by PPARγ-mediated mechanism.

Cardiac remodeling is the primary pathological feature of chronic heart failure (HF). Exploring the characteristics of cardiac remodeling in the very early stages of HF and identifying targets for intervention are essential for discovering novel mechanisms and therapeutic strategies. Silent mating type information regulation 2 homolog 3 (SIRT3), as a major mitochondrial nicotinamide adenine dinucleotide (NAD)-dependent deacetylase, is required for mitochondrial metabolism. However, whether SIRT3 plays a role in cardiac remodeling by regulating the biosynthesis of mitochondrial cardiolipin (CL) is unknown. In this study, we induced pressure overload in wild-type (WT) and SIRT3 knockout (SIRT3-/-) mice via transverse aortic constriction (TAC). Compared with WT mouse hearts, the hearts of SIRT3-/- mice exhibited more-pronounced cardiac remodeling and fibrosis, greater reactive oxygen species (ROS) production, decreased mitochondrial-membrane potential (ΔΨm), and abnormal mitochondrial morphology after TAC. Furthermore, SIRT3 deletion aggravated TAC-induced decrease in total CL content, which might be associated with the downregulation of the CL synthesis related enzymes cardiolipin synthase 1 (CRLS1) and phospholipid-lysophospholipid transacylase (TAFAZZIN). In our in vitro experiments, SIRT3 overexpression prevented angiotensin II (AngII)- induced aberrant mitochondrial function, CL biosynthesis disorder, and peroxisome proliferator-activated receptor gamma (PPARγ) downregulation in cardiomyocytes; meanwhile, SIRT3 knockdown exacerbated these effects. Moreover, the addition of GW9662, a PPARγ antagonist, partially counteracted the beneficial effects of SIRT3 overexpression. In conclusion, SIRT3 regulated PPARγ-mediated CL biosynthesis, maintained the structure and function of mitochondria, and thereby protected the myocardium against cardiac remodeling.

Lipid-Binding Regions within PKC-Related Serine/Threonine Protein Kinase N1 (PKN1) Required for Its Regulation.

PKC-related serine/threonine protein kinase N1 (PKN1) is a protease/lipid-activated protein kinase that acts downstream of the RhoA and Rac1 pathways. PKN1 comprises unique regulatory, hinge region, and PKC homologous catalytic domains. The regulatory domain harbors two homologous regions, i.e., HR1 and C2-like. HR1 consists of three heptad repeats (HR1a, HR1b, and HR1c), with PKN1-(HR1a) hosting an amphipathic high-affinity cardiolipin-binding site for phospholipid interactions. Cardiolipin and C18:1 oleic acid are the most potent lipid activators of PKN1. PKN1-(C2) contains a pseudosubstrate sequence overlapping that of C20:4 arachidonic acid. However, the cardiolipin-binding site(s) within PKN1-(C2) and the respective binding properties remain unclear. Herein, we reveal (i) that the primary PKN1-(C2) sequence contains conserved amphipathic cardiolipin-binding motif(s); (ii) that trimeric PKN1-(C2) predominantly adopts a ß-stranded conformation; (iii) that two distinct types of cardiolipin (or phosphatidic acid) binding occur, with the hydrophobic component playing a key role at higher salt levels; (iv) the multiplicity of C18 fatty acid binding to PKN1-(C2); and (v) the relevance of our lipid-binding parameters for PKN1-(C2) in terms of kinetic parameters previously determined for the full-length PKN1 enzyme. Thus, our discoveries create opportunities to design specific mammalian cell inhibitors that disrupt the localization of membrane-associated PKN1 signaling molecules.

The phospholipids cardiolipin and phosphatidylethanolamine differentially regulate MDC biogenesis.

Cells utilize multiple mechanisms to maintain mitochondrial homeostasis. We recently characterized a pathway that remodels mitochondria in response to metabolic alterations and protein overload stress. This remodeling occurs via the formation of large membranous structures from the mitochondrial outer membrane called mitochondrial-derived compartments (MDCs), which are eventually released from mitochondria and degraded. Here, we conducted a microscopy-based screen in budding yeast to identify factors that regulate MDC formation. We found that two phospholipids, cardiolipin (CL) and phosphatidylethanolamine (PE), differentially regulate MDC biogenesis. CL depletion impairs MDC biogenesis, whereas blocking mitochondrial PE production leads to constitutive MDC formation. Additionally, in response to metabolic MDC activators, cellular and mitochondrial PE declines, and overexpressing mitochondrial PE synthesis enzymes suppress MDC biogenesis. Altogether, our data indicate a requirement for CL in MDC biogenesis and suggest that PE depletion may stimulate MDC formation downstream of MDC-inducing metabolic stress.

The role of cardiolipin and cytochrome c in mitochondrial metabolism of cancer cells determined by Raman imaging: in vitro study on the brain glioblastoma U-87 MG cell line.

In this paper, we present Raman imaging as a non-invasive approach for studying changes in mitochondrial metabolism caused by cardiolipin-cytochrome c interactions. We investigated the effect of mitochondrial dysregulation on cardiolipin (CL) and cytochrome c (Cyt c) interactions for a brain cancer cell line (U-87 MG). Mitochondrial metabolism was monitored by checking the intensities of the Raman bands at 750 cm-1, 1126 cm-1, 1310 cm-1, 1337 cm-1, 1444 cm-1 and 1584 cm-1. The presented results indicate that under pathological conditions, the content and redox status of Cyt c in mitochondria can be used as a Raman marker to characterize changes in cellular metabolism. This work provides evidence that cardiolipin-cytochrome c interactions are crucial for mitochondrial energy homeostasis by controlling the redox status of Cyt c in the electron transport chain, switching from disabling Cyt c reduction and enabling peroxidase activity. This paper provides experimental support for the hypothesis of how cardiolipin-cytochrome c interactions regulate electron transfer in the respiratory chain, apoptosis and mROS production in mitochondria.

The unusual substrate specificity of Escherichia coli cardiolipin synthase C does not require the product of the transcriptionally engaged ymdB gene.

Polycistronic transcription and translation of ymdB-clsC have been thought to be required for full activity of ClsC. The authentic initiation codon of the clsC gene is present within the open reading frame of the upstream located ymdB gene. ClsC translated from authentic initiation codon drives cardiolipin (CL) synthesis without transcriptionally paired YmdB. YmdB is not necessary for the substrate specificity of ClsC utilizing phosphatidylethanolamine (PE) as a co-substrate.

Cardiolipin Membranes Promote Cytochrome c Transformation of Polycyclic Aromatic Hydrocarbons and Their In Vivo Metabolites.

The catalytic properties of cytochrome c (Cc) have captured great interest in respect to mitochondrial physiology and apoptosis, and hold potential for novel enzymatic bioremediation systems. Nevertheless, its contribution to the metabolism of environmental toxicants remains unstudied. Human exposure to polycyclic aromatic hydrocarbons (PAHs) has been associated with impactful diseases, and animal models have unveiled concerning signs of PAHs' toxicity to mitochondria. In this work, a series of eight PAHs with ionization potentials between 7.2 and 8.1 eV were used to challenge the catalytic ability of Cc and to evaluate the effect of vesicles containing cardiolipin mimicking mitochondrial membranes activating the peroxidase activity of Cc. With moderate levels of H2O2 and at pH 7.0, Cc catalyzed the oxidation of toxic PAHs, such as benzo[a]pyrene, anthracene, and benzo[a]anthracene, and the cardiolipin-containing membranes clearly increased the PAH conversions. Our results also demonstrate for the first time that Cc and Cc-cardiolipin complexes efficiently transformed the PAH metabolites 2-hydroxynaphthalene and 1-hydroxypyrene. In comparison to horseradish peroxidase, Cc was shown to reach more potent oxidizing states and react with PAHs with ionization potentials up to 7.70 eV, including pyrene and acenaphthene. Spectral assays indicated that anthracene binds to Cc, and docking simulations proposed possible binding sites positioning anthracene for oxidation. The results give support to the participation of Cc in the metabolism of PAHs, especially in mitochondria, and encourage further investigation of the molecular interaction between PAHs and Cc.

Age-dependent loss of Crls1 causes myopathy and skeletal muscle regeneration failure.

Skeletal muscle aging results in the gradual suppression of myogenesis, leading to muscle mass loss. However, the specific role of cardiolipin in myogenesis has not been determined. This study investigated the crucial role of mitochondrial cardiolipin and cardiolipin synthase 1 (Crls1) in age-related muscle deterioration and myogenesis. Our findings demonstrated that cardiolipin and Crls1 are downregulated in aged skeletal muscle. Moreover, the knockdown of Crls1 in myoblasts reduced mitochondrial mass, activity, and OXPHOS complex IV expression and disrupted the structure of the mitochondrial cristae. AAV9-shCrls1-mediated downregulation of Crls1 impaired muscle regeneration in a mouse model of cardiotoxin (CTX)-induced muscle damage, whereas AAV9-mCrls1-mediated Crls1 overexpression improved regeneration. Overall, our results highlight that the age-dependent decrease in CRLS1 expression contributes to muscle loss by diminishing mitochondrial quality in skeletal muscle myoblasts. Hence, modulating CRLS1 expression is a promising therapeutic strategy for mitigating muscle deterioration associated with aging, suggesting potential avenues for developing interventions to improve overall muscle health and quality of life in elderly individuals.

Decreased pyruvate dehydrogenase activity in Tafazzin-deficient cells is caused by dysregulation of pyruvate dehydrogenase phosphatase 1 (PDP1).

Cardiolipin (CL), the signature lipid of the mitochondrial inner membrane, is critical for maintaining optimal mitochondrial function and bioenergetics. Disruption of CL metabolism, caused by mutations in the CL remodeling enzyme TAFAZZIN, results in the life-threatening disorder Barth syndrome (BTHS). While the clinical manifestations of BTHS, such as dilated cardiomyopathy and skeletal myopathy, point to defects in mitochondrial bioenergetics, the disorder is also characterized by broad metabolic dysregulation, including abnormal levels of metabolites associated with the tricarboxylic acid (TCA) cycle. Recent studies have identified the inhibition of pyruvate dehydrogenase (PDH), the gatekeeper enzyme for TCA cycle carbon influx, as a key deficiency in various BTHS model systems. However, the molecular mechanisms linking aberrant CL remodeling, particularly the primary, direct consequence of reduced tetralinoleoyl-CL (TLCL) levels, to PDH activity deficiency are not yet understood. In the current study, we found that remodeled TLCL promotes PDH function by directly binding to and enhancing the activity of PDH phosphatase 1 (PDP1). This is supported by our findings that TLCL uniquely activates PDH in a dose-dependent manner, TLCL binds to PDP1 in vitro, TLCL-mediated PDH activation is attenuated in the presence of phosphatase inhibitor, and PDP1 activity is decreased in Tafazzin-knockout (TAZ-KO) C2C12 myoblasts. Additionally, we observed decreased mitochondrial calcium levels in TAZ-KO cells and treating TAZ-KO cells with calcium lactate (CaLac) increases mitochondrial calcium and restores PDH activity and mitochondrial oxygen consumption rate. Based on our findings, we conclude that reduced mitochondrial calcium levels and decreased binding of PDP1 to TLCL contribute to decreased PDP1 activity in TAZ-KO cells.

Identification of MIMAS, a multifunctional mega-assembly integrating metabolic and respiratory biogenesis factors of mitochondria.

The mitochondrial inner membrane plays central roles in bioenergetics and metabolism and contains several established membrane protein complexes. Here, we report the identification of a mega-complex of the inner membrane, termed mitochondrial multifunctional assembly (MIMAS). Its large size of 3 MDa explains why MIMAS has escaped detection in the analysis of mitochondria so far. MIMAS combines proteins of diverse functions from respiratory chain assembly to metabolite transport, dehydrogenases, and lipid biosynthesis but not the large established supercomplexes of the respiratory chain, ATP synthase, or prohibitin scaffold. MIMAS integrity depends on the non-bilayer phospholipid phosphatidylethanolamine, in contrast to respiratory supercomplexes whose stability depends on cardiolipin. Our findings suggest that MIMAS forms a protein-lipid mega-assembly in the mitochondrial inner membrane that integrates respiratory biogenesis and metabolic processes in a multifunctional platform.

Kaempferol Improves Cardiolipin and ATP in Hepatic Cells: A Cellular Model Perspective in the Context of Metabolic Dysfunction-Associated Steatotic Liver Disease.

Targeting mitochondrial function is a promising approach to prevent metabolic dysfunction-associated steatotic liver disease (MASLD). Cardiolipin (CL) is a unique lipid comprising four fatty acyl chains localized in the mitochondrial inner membrane. CL is a crucial phospholipid in mitochondrial function, and MASLD exhibits CL-related anomalies. Kaempferol (KMP), a natural flavonoid, has hepatoprotective and mitochondrial function-improving effects; however, its influence on CL metabolism in fatty liver conditions is unknown. In this study, we investigated the effects of KMP on mitochondrial function, focusing on CL metabolism in a fatty liver cell model (linoleic-acid-loaded C3A cell). KMP promoted mitochondrial respiratory functions such as ATP production, basal respiration, and proton leak. KMP also increased the gene expression levels of CPT1A and PPARGC1A, which are involved in mitochondrial ß-oxidation. Comprehensive quantification of CL species and related molecules via liquid chromatography/mass spectrometry showed that KMP increased not only total CL content but also CL72:8, which strongly favors ATP production. Furthermore, KMP improved the monolysocardiolipin (MLCL)/CL ratio, an indicator of mitochondrial function. Our results suggest that KMP promotes energy production in a fatty liver cell model, associated with improvement in mitochondrial CL profile, and can serve as a potential nutrition factor in preventing MASLD.

An upstream open reading frame (5'-uORF) links oxidative stress to translational control of ALCAT1 through phosphorylation of eIF2α.

Acyl-CoA:lysocardiolipin acyltransferase 1 (ALCAT1) is an enzyme that promotes mitochondrial dysfunction by catalyzing pathological remodeling of cardiolipin. Upregulation of ALCAT1 protein expression by oxidative stress is implicated in the pathogenesis of age-related metabolic diseases, but the underlying molecular mechanisms remain elusive. In this study, we identified a highly conserved upstream open reading frame (uORF) at the 5'-untranslated region (5'-UTR) of ALCAT1 mRNA as a key regulator of ALCAT1 expression in response to oxidative stress. We show that the uORF serves as a decoy that prevents translation initiation of ALCAT1 under homeostatic condition. The inhibitory activity of the uORF on ALCAT1 mRNA translation is mitigated by oxidative stress but not ER stress, which requires the phosphorylation of eukaryotic translation initiation factor 2α (eIF2α). Consequently, ablation of uORF or eIF2α phosphorylation at Ser51 renders ALCAT1 protein expression unresponsive to induction by oxidative stress. Taken together, our data show that the uORF links oxidative stress to translation control of ALCAT1 mRNAs through phosphorylation of eIF2α at Ser51.

Mitochondria-Specific Molecular Crosstalk between Ferroptosis and Apoptosis Revealed by In Situ Raman Spectroscopy.

Ferroptosis and apoptosis are two types of regulated cell death that are closely associated with the pathophysiological processes of many diseases. The significance of ferroptosis-apoptosis crosstalk in cell fate determination has been reported, but the underlying molecular mechanisms are poorly understood. Herein mitochondria-mediated molecular crosstalk is explored. Based on a comprehensive spectroscopic investigation and mass spectrometry, cytochrome c-involved Fenton-like reactions and lipid peroxidation are revealed. More importantly, cytochrome c is found to induce ROS-independent and cardiolipin-specific lipid peroxidation depending on its redox state. In situ Raman spectroscopy unveiled that erastin can interrupt membrane permeability, specifically through cardiolipin, facilitating cytochrome c release from the mitochondria. Details of the erastin-cardiolipin interaction are determined using molecular dynamics simulations. This study provides novel insights into how molecular crosstalk occurs around mitochondrial membranes to trigger ferroptosis and apoptosis, with significant implications for the rational design of mitochondria-targeted cell death reducers in cancer therapy.

Gasdermin D triggers cardiolipin-driven mitochondrial damage and pyroptosis.

In a remarkable recent study, Miao et al. reveal that gasdermin D N-terminal (GSDMD-NT) instigates mitochondrial damage in pyroptosis by forming pores in inner and outer mitochondrial membranes (OMMs). The authors highlight the key role of mitochondrial cardiolipin in the action of GSDMD-NT, and significantly advance our understanding of this inflammatory cell death mechanism.

Effect of proline content and histidine ligation on the dynamics of Ω-loop D and the peroxidase activity of iso-1-cytochrome c.

To study how proline residues affect the dynamics of Ω-loop D (residues 70 to 85) of cytochrome c, we prepared G83P and G83A variants of yeast iso-1-cytochrome c (iso-1-Cytc) in the presence and absence of a K73H mutation. Ω-loop D is important in controlling both the electron transfer function of Cytc and the peroxidase activity of Cytc used in apoptosis because it provides the Met80 heme ligand. The G83P and G83A mutations have no effect on the global stability of iso-1-Cytc in presence or absence of the K73H mutation. However, both mutations destabilize the His73-mediated alkaline conformer relative to the native state. pH jump stopped-flow experiments show that the dynamics of the His73-mediated alkaline transition are significantly enhanced by the G83P mutation. Gated electron transfer studies show that the enhanced dynamics result from an increased rate of return to the native state, whereas the rate of loss of Met80 ligation is unchanged by the G83P mutation. Thus, the G83P substitution does not stiffen the conformation of the native state. Because bis-His heme ligation occurs when Cytc binds to cardiolipin-containing membranes, we studied the effect of His73 ligation on the peroxidase activity of Cytc, which acts as an early signal in apoptosis by causing oxygenation of cardiolipin. We find that the His73 alkaline conformer suppresses the peroxidase activity of Cytc. Thus, the bis-His ligated state of Cytc formed upon binding to cardiolipin is a negative effector for the peroxidase activity of Cytc early in apoptosis.

Two mitochondrial DNA polymorphisms modulate cardiolipin binding and lead to synthetic lethality.

Genetic screens have been used extensively to probe interactions between nuclear genes and their impact on phenotypes. Probing interactions between mitochondrial genes and their phenotypic outcome, however, has not been possible due to a lack of tools to map the responsible polymorphisms. Here, using a toolkit we previously established in Drosophila, we isolate over 300 recombinant mitochondrial genomes and map a naturally occurring polymorphism at the cytochrome c oxidase III residue 109 (CoIII109) that fully rescues the lethality and other defects associated with a point mutation in cytochrome c oxidase I (CoIT300I). Through lipidomics profiling, biochemical assays and phenotypic analyses, we show that the CoIII109 polymorphism modulates cardiolipin binding to prevent complex IV instability caused by the CoIT300I mutation. This study demonstrates the feasibility of genetic interaction screens in animal mitochondrial DNA. It unwraps the complex intra-genomic interplays underlying disorders linked to mitochondrial DNA and how they influence disease expression.

ALCAT1-mediated abnormal cardiolipin remodelling promotes mitochondrial injury in podocytes in diabetic kidney disease.

BACKGROUND: Cardiolipin (CL) plays a critical role in maintaining mitochondrial membrane integrity and overall mitochondrial homeostasis. Recent studies have suggested that mitochondrial damage resulting from abnormal cardiolipin remodelling is associated with the pathogenesis of diabetic kidney disease (DKD). Acyl-coenzyme A:lyso-cardiolipin acyltransferase-1 (ALCAT1) was confirmed to be involved in the progression of Parkinson's disease, diet-induced obesity and other ageing-related diseases by regulating pathological cardiolipin remodelling. Thus, the purpose of this investigation was to determine the role of ALCAT1-mediated CL remodelling in DKD and to explore the potential underlying mechanism. METHODS: In vivo study, the mitochondrial structure was examined by transmission electron microscopy (TEM). The colocalization of ALCAT1 and synaptopodin was evaluated by double immunolabelling. Western blotting (WB) was performed to assess ALCAT1 expression in glomeruli. Lipidomics analysis was conducted to evaluate the composition of reconstructed cardiolipins. In vitro study, the lipidomics, TEM and WB analyses were similar to those in vivo. Mitochondrial function was evaluated by measuring the mitochondrial membrane potential (MMP) and the production of ATP and ROS. RESULTS: Here, we showed that increased oxidized cardiolipin (ox-CL) and significant mitochondrial damage were accompanied by increased ALCAT1 expression in the glomeruli of patients with DKD. Similar results were found in db/db mouse kidneys and in cultured podocytes stimulated with high glucose (HG). ALCAT1 deficiency effectively prevented HG-induced ox-CL production and mitochondrial damage in podocytes. In contrast, ALCAT1 upregulation enhanced ox-CL levels and podocyte mitochondrial dysfunction. Moreover, treatment with the cardiolipin antioxidant SS-31 markedly inhibited mitochondrial dysfunction and cell injury, and SS-31 treatment partly reversed the damage mediated by ALCAT1 overexpression. We further found that ALCAT1 could mediate the key regulators of mitochondrial dynamics and mitophagy through the AMPK pathway. CONCLUSIONS: Collectively, our studies demonstrated that ALCAT1-mediated cardiolipin remodelling played a crucial role in DKD, which might provide new insights for DKD treatment. Video Abstract.

Curvature sensing lipid dynamics in a mitochondrial inner membrane model.

Membrane curvature is essential for many cellular structures and processes, and factors such as leaflet asymmetry, lipid composition, and proteins all play important roles. Cardiolipin is the signature lipid of mitochondrial membranes and is essential for maintaining the highly curved shapes of the inner mitochondrial membrane (IMM) and the spatial arrangement of membrane proteins. In this study, we investigate the partitioning behavior of various lipids present in the IMM using coarse-grained molecular dynamics simulations. This study explores curved bilayer systems containing phosphatidylcholine (PC), phosphatidylethanolamine (PE), and cardiolipin (CDL) in binary and ternary component mixtures. Curvature properties such as mean and Gaussian curvatures, as well as the distribution of lipids into the various curved regions of the cristae models, are quantified. Overall, this work represents an advance beyond previous studies on lipid curvature sensing by simulating these systems in a geometry that has the morphological features and scales of curvature consistent with regions of the IMM. We find that CDL has a stronger preference for accumulating in regions of negative curvature than PE lipids, in agreement with previous results. Furthermore, we find lipid partitioning propensity is dominated by sensitivity to mean curvature, while there is a weaker correlation with Gaussian curvature.