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ELife Jun 2024During macroautophagy, cytoplasmic constituents are engulfed by autophagosomes. Lysosomes fuse with closed autophagosomes but not with unclosed intermediate structures....
During macroautophagy, cytoplasmic constituents are engulfed by autophagosomes. Lysosomes fuse with closed autophagosomes but not with unclosed intermediate structures. This is achieved in part by the late recruitment of the autophagosomal SNARE syntaxin 17 (STX17) to mature autophagosomes. However, how STX17 recognizes autophagosome maturation is not known. Here, we show that this temporally regulated recruitment of STX17 depends on the positively charged C-terminal region of STX17. Consistent with this finding, mature autophagosomes are more negatively charged compared with unclosed intermediate structures. This electrostatic maturation of autophagosomes is likely driven by the accumulation of phosphatidylinositol 4-phosphate (PI4P) in the autophagosomal membrane. Accordingly, dephosphorylation of autophagosomal PI4P prevents the association of STX17 to autophagosomes. Furthermore, molecular dynamics simulations support PI4P-dependent membrane insertion of the transmembrane helices of STX17. Based on these findings, we propose a model in which STX17 recruitment to mature autophagosomes is temporally regulated by a PI4P-driven change in the surface charge of autophagosomes.
Topics: Qa-SNARE Proteins; Autophagosomes; Phosphatidylinositol Phosphates; Humans; Molecular Dynamics Simulation; Autophagy
PubMed: 38831696
DOI: 10.7554/eLife.92189 -
Nature Communications Jun 2024Improved biomarkers are needed for pediatric inflammatory bowel disease. Here we identify a diagnostic lipidomic signature for pediatric inflammatory bowel disease by...
Improved biomarkers are needed for pediatric inflammatory bowel disease. Here we identify a diagnostic lipidomic signature for pediatric inflammatory bowel disease by analyzing blood samples from a discovery cohort of incident treatment-naïve pediatric patients and validating findings in an independent inception cohort. The lipidomic signature comprising of only lactosyl ceramide (d18:1/16:0) and phosphatidylcholine (18:0p/22:6) improves the diagnostic prediction compared with high-sensitivity C-reactive protein. Adding high-sensitivity C-reactive protein to the signature does not improve its performance. In patients providing a stool sample, the diagnostic performance of the lipidomic signature and fecal calprotectin, a marker of gastrointestinal inflammation, does not substantially differ. Upon investigation in a third pediatric cohort, the findings of increased lactosyl ceramide (d18:1/16:0) and decreased phosphatidylcholine (18:0p/22:6) absolute concentrations are confirmed. Translation of the lipidomic signature into a scalable diagnostic blood test for pediatric inflammatory bowel disease has the potential to support clinical decision making.
Topics: Humans; Child; Lipidomics; Male; Female; Inflammatory Bowel Diseases; Biomarkers; Adolescent; Feces; Phosphatidylcholines; C-Reactive Protein; Child, Preschool; Leukocyte L1 Antigen Complex; Cohort Studies
PubMed: 38830848
DOI: 10.1038/s41467-024-48763-7 -
BioRxiv : the Preprint Server For... May 2024Exercise training is thought to improve the mitochondrial energy efficiency of skeletal muscle. Some studies suggest exercise training increases the efficiency for ATP...
BACKGROUND
Exercise training is thought to improve the mitochondrial energy efficiency of skeletal muscle. Some studies suggest exercise training increases the efficiency for ATP synthesis by oxidative phosphorylation (OXPHOS), but the molecular mechanisms are unclear. We have previously shown that exercise remodels the lipid composition of mitochondrial membranes, and some of these changes could contribute to improved OXPHOS efficiency (ATP produced by O2 consumed or P/O). Peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) is a transcriptional co-activator that coordinately regulates exercise-induced adaptations including mitochondria. We hypothesized that increased PGC-1α activity is sufficient to remodel mitochondrial membrane lipids and promote energy efficiency.
METHODS
Mice with skeletal muscle-specific overexpression of PGC-1α (MCK-PGC-1α) and their wildtype littermates were used for this study. Lipid mass spectrometry and quantitative PCR were used to assess muscle mitochondrial lipid composition and their biosynthesis pathway. The abundance of OXPHOS enzymes was determined by western blot assay. High-resolution respirometry and fluorometry analysis were used to characterize mitochondrial bioenergetics (ATP production, O2 consumption, and P/O) for permeabilized fibers and isolated mitochondria.
RESULTS
Lipidomic analyses of skeletal muscle mitochondria from wildtype and MCK-PGC-1α mice revealed that PGC-1α increases the concentrations of cone-shaped lipids such as phosphatidylethanolamine (PE), cardiolipin (CL), and lysophospholipids, while decreases the concentrations of phosphatidylcholine (PC), phosphatidylinositol (PI) and phosphatidic acid (PA). However, while PGC-1α overexpression increased the abundance of OXPHOS enzymes in skeletal muscle and the rate of O2 consumption (O2), P/O values were unaffected with PGC-1α in permeabilized fibers or isolated mitochondria.
CONCLUSIONS
Collectively, overexpression of PGC-1α promotes the biosynthesis of mitochondrial PE and CL but neither PGC-1α nor the mitochondrial membrane lipid remodeling induced in MCK-PGC-1α mice is sufficient to increase the efficiency for mitochondrial ATP synthesis. These findings suggest that exercise training may increase OXPHOS efficiency by a PGC-1α-independent mechanism, and question the hypothesis that mitochondrial lipids directly affect OXPHOS enzymes to improve efficiency for ATP synthesis.
PubMed: 38826268
DOI: 10.1101/2024.05.22.595374 -
Journal of Oleo Science 2024Bicellar mixtures containing diacetylene molecules, such as diynoic acids, can be used as parent materials for functional membranes. A bicellar mixture consisting of a...
Bicellar mixtures containing diacetylene molecules, such as diynoic acids, can be used as parent materials for functional membranes. A bicellar mixture consisting of a diynoic acid-10,12-tricosadiynoic acid (TCDA)-, a phospholipid-1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)-, and a detergent-3-[(3-cholamidopropyl) dimethylammonio]-2-hydroxypropanesulfonate (CHAPSO)-was evaluated for its morphology and packing of TCDA molecules in its bicellar mixture. A TCDA/DMPC vesicle was prepared at different molar ratios, TCDA/DMPC = 2/8, 5/5, and 8/2; a TCDA/DMPC/CHAPSO bicellar mixture was prepared by mixing a CHAPSO solution with a TCDA/DMPC vesicle solution as a detergent at different composition ratios, x = [TCDA/DMPC]/([TCDA/DMPC]+[CHAPSO]), of 1.0, 0.70, 0.50, and 0.30. A DMPC molecule formed a bilayer membrane structure and was used to suppress its precipitation. The packing density of the TCDA/DMPC/CHAPSO bicellar mixtures was increased by mixing a CHAPSO molecule in x = 1.0 to 0.70 or 0.50. A TEM image of a TCDA/DMPC/CHAPSO bicellar mixture showed many discoidal assemblies at x = 0.5 of TCDA/DMPC = 5/5. Polymerization of the TCDA molecules in the bicellar mixture by UV light suggested an ordered arrangement of TCDA. Polymerization at x = 0.70 and 0.50 correlated with improved packing density.
Topics: Dimyristoylphosphatidylcholine; Detergents; Lipid Bilayers; Phase Separation
PubMed: 38825541
DOI: 10.5650/jos.ess24006 -
The Journal of Biological Chemistry May 2024The nuclear envelope (NE) is a permeable barrier that maintains nuclear-cytoplasmic compartmentalization and ensures nuclear function; however, it ruptures in various...
The nuclear envelope (NE) is a permeable barrier that maintains nuclear-cytoplasmic compartmentalization and ensures nuclear function; however, it ruptures in various situations such as mechanical stress and mitosis. Although the protein components for sealing a ruptured NE have been identified, the mechanism by which lipid components are involved in this process remains to be elucidated. Here, we found that an inner nuclear membrane (INM) protein Bqt4 directly interacts with phosphatidic acid (PA) and serves as a platform for NE maintenance in the fission yeast Schizosaccharomyces pombe. The intrinsically disordered region (IDR) of Bqt4, proximal to the transmembrane domain, binds to PA and forms a solid aggregate in vitro. Excessive accumulation of Bqt4 IDR in INM results in membrane overproliferation and lipid droplet formation in the nucleus, leading to centromere dissociation from the NE and chromosome missegregation. Our findings suggest that Bqt4 IDR controls nuclear membrane homeostasis by recruiting PA to the INM, thereby maintaining the structural integrity of the NE.
PubMed: 38825008
DOI: 10.1016/j.jbc.2024.107430 -
Biophysical Journal May 2024The asymmetry of membranes has a significant impact on their biophysical characteristics and behavior. This study investigates the composition and mechanical properties...
The asymmetry of membranes has a significant impact on their biophysical characteristics and behavior. This study investigates the composition and mechanical properties of symmetric and asymmetric membranes in giant unilamellar vesicles (GUVs) made of palmitoyloleoyl phosphatidylcholine (POPC) and palmitoyloleoyl phosphatidic acid (POPA). A combination of fluorescence quantification, zeta potential measurements, micropipette aspiration, and bilayer molecular dynamics simulations are used to characterize these membranes. The outer leaflet composition in vesicles is found consistent across the two preparation methods we employed, namely electroformation and inverted emulsion transfer. However, characterizing the inner leaflet poses challenges. Micropipette aspiration of GUVs show that oil residues do not substantially alter membrane elasticity, but simulations reveal increased membrane thickness and decreased interleaflet coupling in the presence of oil. Asymmetric membranes with a POPC:POPA mixture in the outer leaflet and POPC in the inner leaflet display similar stretching elasticity values to symmetric POPC:POPA membranes, suggesting potential POPA insertion into the inner leaflet during vesicle formation and suppressed asymmetry. The inverse compositional asymmetry, with POPC in the outer leaflet and POPC:POPA in the inner one yield less stretchable membranes with higher compressibility modulus compared with their symmetric counterparts. Challenges in achieving and predicting compositional correspondence highlight the limitations of phase-transfer-based methods. In addition, caution is advised when using fluorescently labeled lipids (even at low fractions of 0.5 mol %), as unexpected gel-like domains in symmetric POPC:POPA membranes were observed only with a specific type of labeled DOPE (dioleoylphosphatidylethanolamine) and the same fraction of unlabeled DOPE. The latter suggest that such domain formation may result from interactions between lipids and membrane fluorescent probes. Overall, this study underscores the complexity of factors influencing GUV membrane asymmetry, emphasizing the need for further research and improvement of characterization techniques.
PubMed: 38822521
DOI: 10.1016/j.bpj.2024.05.031 -
Journal of Hazardous Materials Aug 2024The fetus and infants are particularly vulnerable to Cadmium (Cd) due to the immaturity of the blood-brain barrier. In utero and early life exposure to Cd is associated...
PLCβ4 driven by cadmium-exposure during gestation and lactation contributes to cognitive deficits by suppressing PIP2/PLCγ1/CREB/BDNF signaling pathway in male offspring.
The fetus and infants are particularly vulnerable to Cadmium (Cd) due to the immaturity of the blood-brain barrier. In utero and early life exposure to Cd is associated with cognitive deficits. Although such exposure has attracted widespread attention, its gender-specificity remains controversial, and there are no reports disclosing the underlying mechanism of gender‑specific neurotoxicity. We extensively evaluated the learning and cognitive functions and synaptic plasticity of male and female rats exposed to maternal Cd. Maternal Cd exposure induced learning and memory deficits in male offspring rats, but not in female offspring rats. PLCβ4 was identified as a critical protein, which might be related to the gender‑specific cognitive deficits in male rats. The up-regulated PLCβ4 competed with PLCγ1 to bind to PIP2, which counteracted the hydrolysis of PIP2 by PLCγ1. The decreased activation of PLCγ1 inhibited the phosphorylation of CREB to reduce BDNF transcription, which consequently resulted in the damage of hippocampal neurons and cognitive deficiency. Moreover, the low level of BDNF promoted AEP activation to induce Aβ deposition in the hippocampus. These findings highlight that PLCβ4 might be a potential target for the therapy of learning and cognitive deficits caused by Cd exposure in early life.
Topics: Animals; Female; Male; Pregnancy; Cadmium; Brain-Derived Neurotrophic Factor; Phospholipase C gamma; Signal Transduction; Cyclic AMP Response Element-Binding Protein; Prenatal Exposure Delayed Effects; Hippocampus; Lactation; Cognitive Dysfunction; Phospholipase C beta; Rats, Sprague-Dawley; Phosphatidylinositol 4,5-Diphosphate; Maternal Exposure; Rats
PubMed: 38820747
DOI: 10.1016/j.jhazmat.2024.134756 -
PloS One 2024Changes in alcohol consumption may affect older adults' health. We examined prevalence and changes in the alcohol consumption of older women and men (≥65 years) in...
BACKGROUND
Changes in alcohol consumption may affect older adults' health. We examined prevalence and changes in the alcohol consumption of older women and men (≥65 years) in Norway over a 24-year period.
METHODS
Data from three population-based health surveys (The Trøndelag Health Study-HUNT2 1995-97, HUNT3 2006-08, HUNT4 2017-19) were used. Alcohol consumption was measured using self-reported measures and an objective measure of alcohol consumption (Phosphatidylethanol 16:0/18:1, PEth). Self-reported lifetime abstinence, former drinking, current drinking, frequent drinking (≥4 times/week), and risk drinking (≥8 units/week) were measured. The PEth concentrations were stratified: <0.03 μmol/l (abstinence/very low level of alcohol consumption); >0.06 μmol/l (indicating >1 unit/day); >0.10 μmol/l (indicating >3 units/day), and >0.30 μmol/l (heavy alcohol consumption).
RESULTS
In HUNT4, the prevalence of self-reported lifetime abstinence, frequent drinking, and risk drinking was 5.2%, 4.4%, and 5.6%, respectively, while prevalence of PEth <0.03 μmol/l was 68.1% and PEth >0.06 μmol/l was 21.2%. Over the course of the three surveys, the prevalence of self-reported lifetime abstinence decreased, while the prevalence of frequent drinking and risk drinking increased. Men were less often abstainers and more often frequent and risky drinkers than women in all three surveys. Gender differences for abstinence and current drinking reduced with time. From HUNT3 to HUNT4, the prevalence of PEth <0.03 μmol/l decreased, while the prevalence of PEth >0.06 μmol/l increased. Men compared to women, had less often PEth <0.03 μmol/l and more often PEth >0.06 and >0.10 μmol/l in HUNT3 and HUNT4. Women and men ≥75 years were just as likely to have PEth >0.30 μmol/l in HUNT4. The gender differences in PEth concentrations were reduced in HUNT4 among those aged 70-74 years or ≥75 years.
CONCLUSION
Alcohol consumption has increased among Norwegian older adults over a 24-year period, but at a slower pace during the last decade.
Topics: Humans; Male; Female; Aged; Alcohol Drinking; Self Report; Norway; Prevalence; Glycerophospholipids; Aged, 80 and over; Health Surveys
PubMed: 38820445
DOI: 10.1371/journal.pone.0304714 -
Cellular and Molecular Life Sciences :... May 2024The glycosylphosphatidylinositol (GPI) biosynthetic pathway in the endoplasmic reticulum (ER) is crucial for generating GPI-anchored proteins (GPI-APs), which are...
The glycosylphosphatidylinositol (GPI) biosynthetic pathway in the endoplasmic reticulum (ER) is crucial for generating GPI-anchored proteins (GPI-APs), which are translocated to the cell surface and play a vital role in cell signaling and adhesion. This study focuses on two integral components of the GPI pathway, the PIGL and PIGF proteins, and their significance in trophoblast biology. We show that GPI pathway mutations impact on placental development impairing the differentiation of the syncytiotrophoblast (SynT), and especially the SynT-II layer, which is essential for the establishment of the definitive nutrient exchange area within the placental labyrinth. CRISPR/Cas9 knockout of Pigl and Pigf in mouse trophoblast stem cells (mTSCs) confirms the role of these GPI enzymes in syncytiotrophoblast differentiation. Mechanistically, impaired GPI-AP generation induces an excessive unfolded protein response (UPR) in the ER in mTSCs growing in stem cell conditions, akin to what is observed in human preeclampsia. Upon differentiation, the impairment of the GPI pathway hinders the induction of WNT signaling for early SynT-II development. Remarkably, the transcriptomic profile of Pigl- and Pigf-deficient cells separates human patient placental samples into preeclampsia and control groups, suggesting an involvement of Pigl and Pigf in establishing a preeclamptic gene signature. Our study unveils the pivotal role of GPI biosynthesis in early placentation and uncovers a new preeclampsia gene expression profile associated with mutations in the GPI biosynthesis pathway, providing novel molecular insights into placental development with implications for enhanced patient stratification and timely interventions.
Topics: Trophoblasts; Female; Pregnancy; Cell Differentiation; Animals; Humans; Mice; Placentation; Glycosylphosphatidylinositols; Placenta; Wnt Signaling Pathway; Pre-Eclampsia; Endoplasmic Reticulum; Biosynthetic Pathways; Unfolded Protein Response; CRISPR-Cas Systems
PubMed: 38819479
DOI: 10.1007/s00018-024-05284-2 -
Journal of Integrative Plant Biology May 2024
PubMed: 38818976
DOI: 10.1111/jipb.13683