Biology subjects

Brouwers, J. F.

Publications and source records attributed to Brouwers, J. F..

6 recordsLinked to original sources

bioRxiv2025

PINK1 regulates cholesterol homeostasis via SCAP phosphorylation in human dopaminergic neurons

Cholesterol is a key lipid enriched in neuronal membranes and essential for signaling and synaptic transmission. An imbalance in cholesterol levels may affect synaptic plasticity and contribute to neurodegeneration. Here, we identify in human dopaminergic neurons a mechanism linking loss of function of the Parkinsons disease (PD) gene PINK1 to altered cholesterol homeostasis. Loss of functional PINK1 impaired SCAP phosphorylation at Ser822 and Ser838, stabilizing SCAP and driving excess cholesterol biosynthesis. Cholesterol accumulated at the plasma membrane and in flotillin-rich lipid rafts, causing reduced neurotransmitter uptake and altering the distribution of dopamine transporter (DAT). Restoring PINK1 expression normalized cholesterol biosynthesis and levels. Moreover, the cholesterol-lowering drugs simvastatin and {beta}-cyclodextrin rescued DAT distribution and neurotransmitter uptake defects. These findings demonstrate that PINK1 influences cholesterol homeostasis through SCAP phosphorylation at Ser822 and Ser838 and that restoring cholesterol levels mitigates phenotypes observed in PINK1 PD neurons. These findings further highlight the cross-talk between mitochondria and lipid homeostasis in PD models, underscoring the relevance of cholesterol levels to dopaminergic functions. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/672574v1_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@165b4d4org.highwire.dtl.DTLVardef@42e3a2org.highwire.dtl.DTLVardef@16ea6f7org.highwire.dtl.DTLVardef@193e170_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG

neuroscience↗

bioRxiv2020

Molecular species selectivity of lipid transport creates a mitochondrial sink for di-unsaturated phospholipids

Mitochondria depend on the import of phospholipid precursors for the biosynthesis of the non-bilayer lipids phosphatidylethanolamine (PE) and cardiolipin required for proper function, yet the mechanism of lipid import remains elusive. Pulse labeling yeast with stable isotope-labeled serine followed by mass spectrometry analysis revealed that mitochondria preferentially import di-unsaturated phosphatidylserine (PS) for conversion to PE by the mitochondrial PS decarboxylase Psd1p. Several protein complexes tethering mitochondria to the endomembrane system have been implicated in lipid transport in yeast, including the endoplasmic reticulum (ER)-mitochondrial encounter structure (ERMES), ER-mitochondria complex (EMC) and the vacuole and mitochondria patch (vCLAMP). By limiting the availability of unsaturated phospholipids through overexpression of the glycerol-3-phosphate acyltransferase Sct1p, conditions were created to investigate the mechanism of lipid transfer and the contribution of the tethering complexes in vivo. Under these conditions, inactivation of ERMES components or the vCLAMP component Vps39p exacerbated the lipid phenotype, indicating that ERMES and Vps39 contribute to the mitochondrial sink for unsaturated acyl chains by mediating transfer of di-unsaturated phospholipids. The results support the concept that intermembrane lipid flow is rate-limited by molecular species-dependent lipid efflux from the donor membrane and driven by the lipid species concentration gradient between donor and acceptor membrane.

biochemistry↗

bioRxiv2019

PINK1 Regulates Dopamine and Lipids at Mitochondria to Maintain Synapses and Neuronal Function

Mitochondrial dysfunction contributes to the pathogenesis of Parkinsons disease but it is not clear why inherent mitochondrial defects lead specifically to the death of dopaminergic neurons of the mid brain. PINK1 is mitochondrial kinase and PINK1 mutations cause early onset Parkinsons disease.\n\nWe found that in neuronal progenitors, PINK1 regulates mitochondrial morphology, mitochondrial contact to the endoplasmic reticulum (ER) and the phosphorylation of Miro1. A compensatory metabolic shift towards lipid synthesis provides mitochondria with the components needed for membrane renewal and oxidative phosphorylation, maintaining the mitochondrial network once mature.\n\nCholesterol is increased by loss of PINK1, promoting overall membrane rigidity. This alters the distribution of phosphorylated DAT at synapses and impairs dopamine uptake. PINK1 is required for the phosphorylation of tyrosine hydroxylase at Ser19, dopamine and calcium homeostasis and dopaminergic pacemaking.\n\nWe suggest a novel mechanism for PINK1 pathogenicity in Parkinsons disease in addition to but not exclusive of mitophagy. We also provide a basis for potential therapeutics by showing that low doses of the cholesterol depleting drug {beta}-cyclodextrin reverse PINK1-specific phenotypes.

neuroscience↗

bioRxiv2018

Schistosoma mansoni does not and cannot oxidize fatty acids, but these are used for biosynthetic purposes instead

Adult schistosomes, parasitic flatworms that cause the tropical disease schistosomiasis, have always been considered to be homolactic fermenters and in their energy metabolism strictly dependent on carbohydrates. However, more recent studies suggested that fatty acid {beta}-oxidation is essential for egg production by adult female Schistosoma mansoni. To address this conundrum, we performed a comprehensive study on the lipid metabolism of S. mansoni. Incubations with [14C]-labelled fatty acids demonstrated that adults, eggs and miracidia of S. mansoni did not oxidize fatty acids, as no 14CO2 production could be detected. We then re-examined the S. mansoni genome using the genes known to be involved in fatty acid oxidation in six eukaryotic model reference species. This showed that the earlier automatically annotated genes for fatty acid oxidation were in fact incorrectly annotated. In a further analysis we could not detect any genes encoding {beta}-oxidation enzymes, which demonstrates that S. mansoni cannot use this pathway in any of its lifecycle stages. The same was true for S. japonicum. Absence of {beta}-oxidation, however, does not imply that fatty acids from the host are not metabolized by schistosomes. Adult schistosomes can use and modify fatty acids from their host for biosynthetic purposes and incorporate them in phospholipids and neutral lipids. Female worms deposit large amounts of these lipids in the eggs they produce, which explains why interference with the lipid metabolism in females will disturb egg formation, even though fatty acid {beta}-oxidation does not occur in schistosomes. Our analyses of S. mansoni further revealed that during the development and maturation of the miracidium inside the egg, changes in lipid composition occur which indicates that fatty acids deposited in the egg by the female worm are used for phospholipid biosynthesis required for membrane formation in the developing miracidium.

biochemistry↗

bioRxiv2018

LION/web: a web-based ontology enrichment tool for lipidomic data analysis

A major challenge for lipidomic analyses is the handling of the large amounts of data and the translation of results to interpret the involvement of lipids in biological systems. We built a new lipid ontology (LION) that associates over 50,000 lipid species to biophysical, chemical and cell biological features. By making use of enrichment algorithms, we used LION to develop a web-based interface (LION/web, www.lipidontology.com) that allows identification of lipid-associated terms in lipidomes. LION/web was validated by analyzing a lipidomic dataset derived from well-characterized sub-cellular fractions of RAW 264.7 macrophages. Comparison of isolated plasma membranes with the microsomal fraction showed a significant enrichment of relevant LION-terms including plasma membrane, headgroup with negative charge, glycerophosphoserines, above average bilayer thickness, and below average lateral diffusion. A second validation was performed by analyzing the membrane fluidity of CHO cells incubated with arachidonic acid. An increase in membrane fluidity was observed both experimentally by using pyrene decanoic acid and by using LION/web, showing significant enrichment of terms associated with high membrane fluidity ('above average, 'very high and 'high lateral diffusion, and 'below average transition temperature). The results demonstrate the functionality of LION/web, which is freely accessible in a platform-independent way.

biochemistry↗

bioRxiv2018

Lipids are the preferred substrate of the protist Naegleria gruberi, relative of a human brain pathogen

Naegleria gruberi is a free-living non-pathogenic amoeboflagellate and relative of Naegleria fowleri, a deadly pathogen causing primary amoebic meningoencephalitis (PAM). A genomic analysis of N. gruberi exists, but physiological evidence for its core energy metabolism or in vivo growth substrates is lacking. Here we show that N. gruberi trophozoites need oxygen for normal functioning and growth and that they furthermore shun both glucose and amino acids as growth substrates. Trophozoite growth depends mainly upon lipid oxidation via a mitochondrial branched respiratory chain, both ends of which require oxygen as final electron acceptor. Growing N. gruberi trophozoites thus have a strictly aerobic energy metabolism with a marked substrate preference for the oxidation of fatty acids. Analyses of N. fowleri genome data and comparison with those of N. gruberi indicate that N. fowleri has the same type of metabolism. Specialization to oxygen-dependent lipid breakdown represents a hitherto unprecedented metabolic strategy in protists.

biochemistry↗