Henk van den Bosch: Chemist and biochemist
2004, Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
Henk van den Bosch is a native of The Netherlands and recently retired from his position as Professor at Utrecht University. This article summarizes the many scientific achievements of Dr. van den Bosch. He enjoys an international reputation for his research on phospholipases A, cardiolipin biosynthesis in eukaryotes, lysophospholipases, phosphatidylcholine biosynthesis for lung surfactant, plasmalogen biosynthesis in peroxisomes, diagnosis of peroxisomal disorders and most recently his work on alkyl-dihydroxyacetone phosphate synthase. During his research career Henk van den Bosch published approximately 280 articles and presented 110 invited lectures.
The mitochondrial permeability transition
1995, BBA - Reviews on Biomembranes
Hepatic secretion of lysophosphatidylcholine: A novel transport system for polyunsaturated fatty acids and choline
1993, The Journal of Nutritional Biochemistry
<sup>31</sup>P nuclear magnetic resonance study of phospholipid metabolites in ischemic liver
1992, Journal of Surgical Research
To assess the metabolic alterations induced by normothermic hepatic ischemia, 31P nuclear magnetic resonance analysis was performed on liver samples using perchloric acid extraction. In particular, phosphomonoesters and phosphodiesters, the intermediary metabolites of membrane phospholipid turnover, were characterized precisely and quantitated. Phosphocholine and phosphoethanolamine, the precursors of phospholipid anabolism, did not change, while the phosphodiesters decreased. In contrast, α-glycerophosphate, which is both a precursor of phospholipid synthesis and the intermediary product of phospholipid degradation, markedly increased following 30 min of normothermic ischemia. These findings suggest that cellular phospholipids are actively degraded during normothermic hepatic ischemia.
Sexual dimorphism in the preferential secretion of unsaturated lysophosphatidylcholine by rat hepatocytes but no secretion by sheep hepatocytes
1991, Biochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism(Video) How toxicants induce toxicity in liver, kidney, lung & brain? (Free notes: Organ toxicology) 2022
(1) Rat and ovine hepatocytes were incubated in monolayer culture with various fatty acids to determine their effects on the composition of the lysophosphatidylcholine that was secreted. (2) No lysophosphatidylcholine was detected in the medium from the ovine hepatocytes even though these cells were hormonally responsive and they secreted phosphatidylcholine and triacylglycerol in very-low-density lipoprotein. (3) Lysophosphatidylcholine was readily detected in the incubation medium of rat hepatocytes. The predominant fatty acids in this lipid were unsaturated. Stearate and arachidonate contributed 15 and 34%, and 24% and 26% of the total fatty acids when hepatocytes from male and female rats were used, respectively. The relative proportions of stearate and arachidonate in the phosphatidylcholine secreted from the hepatocytes were 20 and 14%, and 28 and 21% for the males and females, respectively. The equivalent values for stearate and arachidonate for phosphatidylcholine in the hepatocytes were 18 and 17% and 33 and 22% for male and female rats. These results provide further indications of sex differences in hepatic phospholipid metabolism and extend this to the secretion of phosphatidylcholine and lysophosphatidylcholine. (4) The addition of 1 mM stearate to the incubation medium did not significantly decrease the proportion of arachidonate in the lysophosphatidylcholine obtained from the hepatocytes of the male rats. However, the relative proportion of arachidonate was decreased in incubations that contained 1 mM oleate or linoleate. (5) The results provide evidence that the preferential secretion of unsaturated lysophosphatidylcholine by the liver may provide a system for transporting unsaturated fatty acids and choline to other organs in non-ruminant animals. However, this mechanism may not operate for ruminats.
Preferential lipid association and mode of penetration of apocytochrome c in mixed model membranes as monitored by tryptophanyl fluorescence quenching using brominated phospholipids
1987, BBA - Biomembranes
The fluorescence of the single tryptophan residue at position 59 in apocytochrome c, the biosynthetic precursor of the inner mitochondrial membrane protein cytochrome c, was studied in small unilamellar vesicles composed of phosphatidylserine (PS) and phosphatidylcholine (PC) with or without specifically Br-labelled acyl chains at the sn-2 position. The protein has a very high affinity for PS-containing vesicles (dissociation constant Kd < 1 μM). From the relative quenching efficiency by the brominated phospholipids, it could be concluded that the protein specifically associates with the PS component in mixed vesicles and that maximal quenching occurred with phospholipids in which the bromine was present at the 6,7-position of the 2-acyl chain suggesting that (part of) the bound protein penetrates 7–8 Å deep into the hydrophobic core of the bilayer.
Substrate-modulated Cytochrome P450 17A1 and Cytochrome b5 Interactions Revealed by NMR
Journal of Biological Chemistry, Volume 288, Issue 23, 2013, pp. 17008-17018
The membrane heme protein cytochrome b5 (b5) can enhance, inhibit, or have no effect on cytochrome P450 (P450) catalysis, depending on the specific P450, substrate, and reaction conditions, but the structural basis remains unclear. Here the interactions between the soluble domain of microsomal b5 and the catalytic domain of the bifunctional steroidogenic cytochrome P450 17A1 (CYP17A1) were investigated. CYP17A1 performs both steroid hydroxylation, which is unaffected by b5, and an androgen-forming lyase reaction that is facilitated 10-fold by b5. NMR chemical shift mapping of b5 titrations with CYP17A1 indicates that the interaction occurs in an intermediate exchange regime and identifies charged surface residues involved in the protein/protein interface. The role of these residues is confirmed by disruption of the complex upon mutagenesis of either the anionic b5 residues (Glu-48 or Glu-49) or the corresponding cationic CYP17A1 residues (Arg-347, Arg-358, or Arg-449). Cytochrome b5 binding to CYP17A1 is also mutually exclusive with binding of NADPH-cytochrome P450 reductase. To probe the differential effects of b5 on the two CYP17A1-mediated reactions and, thus, communication between the superficial b5 binding site and the buried CYP17A1 active site, CYP17A1/b5 complex formation was characterized with either hydroxylase or lyase substrates bound to CYP17A1. Significantly, the CYP17A1/b5 interaction is stronger when the hydroxylase substrate pregnenolone is present in the CYP17A1 active site than when the lyase substrate 17α-hydroxypregnenolone is in the active site. These findings form the basis for a clearer understanding of this important interaction by directly measuring the reversible binding of the two proteins, providing evidence of communication between the CYP17A1 active site and the superficial proximal b5 binding site.
Background: Steroidogenic cytochrome P450 17A1 (CYP17A1) performs hydroxylase and lyase reactions, with only the latter facilitated by cytochrome b5.(Video) HDL Metabolism: Reverse cholesterol transport: Why HDL cholesterol is good cholesterol?
Results: NMR mapping confirms the CYP17A1/b5 interface and reveals substrate modulation of the interaction.
Conclusion: Allosteric communication exists between the buried CYP17A1 active site and its peripheral b5 binding site.
Significance: The CYP17A1 reaction mechanism may be governed by proximal conformational control.
Biosynthesis of GDP-fucose and Other Sugar Nucleotides in the Blood Stages of Plasmodium falciparum
Journal of Biological Chemistry, Volume 288, Issue 23, 2013, pp. 16506-16517
Carbohydrate structures play important roles in many biological processes, including cell adhesion, cell-cell communication, and host-pathogen interactions. Sugar nucleotides are activated forms of sugars used by the cell as donors for most glycosylation reactions. Using a liquid chromatography-tandem mass spectrometry-based method, we identified and quantified the pools of UDP-glucose, UDP-galactose, UDP-N-acetylglucosamine, GDP-mannose, and GDP-fucose in Plasmodium falciparum intraerythrocytic life stages. We assembled these data with the in silico functional reconstruction of the parasite metabolic pathways obtained from the P. falciparum annotated genome, exposing new active biosynthetic routes crucial for further glycosylation reactions. Fucose is a sugar present in glycoconjugates often associated with recognition and adhesion events. Thus, the GDP-fucose precursor is essential in a wide variety of organisms. P. falciparum presents homologues of GDP-mannose 4,6-dehydratase and GDP-l-fucose synthase enzymes that are active in vitro, indicating that most GDP-fucose is formed by a de novo pathway that involves the bioconversion of GDP-mannose. Homologues for enzymes involved in a fucose salvage pathway are apparently absent in the P. falciparum genome. This is in agreement with in vivo metabolic labeling experiments showing that fucose is not significantly incorporated by the parasite. Fluorescence microscopy of epitope-tagged versions of P. falciparum GDP-mannose 4,6-dehydratase and GDP-l-fucose synthase expressed in transgenic 3D7 parasites shows that these enzymes localize in the cytoplasm of P. falciparum during the intraerythrocytic developmental cycle. Although the function of fucose in the parasite is not known, the presence of GDP-fucose suggests that the metabolite may be used for further fucosylation reactions.
Background: GDP-fucose and other sugar nucleotide biosynthetic pathways are conserved in the P. falciparum genome.
Results: These pathways are active in the intraerythrocytic life cycle of the parasite.
Conclusion: The parasite biosynthesizes GDP-fucose and other sugar nucleotides not related to the glycosylphosphatidylinositol structures
Significance: Their presence strongly suggests that they are involved in the biosynthesis of glycans not yet characterized.
Mechanism, influencing factors exploration and modelling on the reactive extraction of 2-ketogluconic acid in presence of a phase modifier
Separation and Purification Technology, Volume 255, 2021, Article 117740
Taking into account that limited research has been carried out on the reactive extraction of 2-ketogluconic acid, this study was focused on analyzing the pH dependent extraction performance and the molar ratios of acid and extractant (Amberlite LA-2) dissolved in three solvents with 1-octanol as phase modifier. Back extraction was successfully performed using NaOH solutions. The mechanism of the interfacial reaction in the presence of 1-octanol, pointed out that, indifferent of the pH value and solvent polarity, only one molecule of 2-ketogluconic acid and one of extractant react at the interface. The positive effect of 1-octanol on extraction efficiency was quantified by means of the amplification factor, its maximum values being 2.43 for dichloromethane, 3.67 for butyl acetate and 3.64 for n-heptane. In addition, the process was modelled using statistical regression and Artificial Neural Networks (ANNs) determined with chaos based Differential Evolution algorithm. The best ANN model had a mean squared error for the testing phase of 0.19 and modeled the process with an acceptable error.(Video) Progestogen, progestin, progesterone: Why all the confusion?
Rapid Accumulation of Endogenous Tau Oligomers in a Rat Model of Traumatic Brain Injury: POSSIBLE LINK BETWEEN TRAUMATIC BRAIN INJURY AND SPORADIC TAUOPATHIES
Journal of Biological Chemistry, Volume 288, Issue 23, 2013, pp. 17042-17050
Traumatic brain injury (TBI) is a serious problem that affects millions of people in the United States alone. Multiple concussions or even a single moderate to severe TBI can also predispose individuals to develop a pathologically distinct form of tauopathy-related dementia at an early age. No effective treatments are currently available for TBI or TBI-related dementia; moreover, only recently has insight been gained regarding the mechanisms behind their connection. Here, we used antibodies to detect oligomeric and phosphorylated Tau proteins in a non-transgenic rodent model of parasagittal fluid percussion injury. Oligomeric and phosphorylated Tau proteins were detected 4 and 24 h and 2 weeks post-TBI in injured, but not sham control rats. These findings suggest that diagnostic tools and therapeutics that target only toxic forms of Tau may provide earlier detection and safe, more effective treatments for tauopathies associated with repetitive neurotrauma.
Background: Traumatic brain injury (TBI) contributes to the development tauopathy-related dementia.
Results: Rapid formation of oligomeric and phosphorylated Tau proteins in a rodent model for TBI.
Conclusion: TBI triggers the formation of Tau oligomers, which may represent a link between TBI and sporadic tauopathies.
Significance: The results suggest that targeting Tau oligomers may be useful for the prevention of dementia following TBI.
WDR26 Functions as a Scaffolding Protein to Promote Gβγ-mediated Phospholipase C β2 (PLCβ2) Activation in Leukocytes
Journal of Biological Chemistry, Volume 288, Issue 23, 2013, pp. 16715-16725
We have recently identified WDR26 as a novel WD40 repeat protein that binds Gβγ and promotes Gβγ signaling during leukocyte migration. Here, we have determined the mechanism by which WDR26 enhances Gβγ-mediated phospholipase C β2 (PLCβ2) activation in leukocytes. We show that WDR26 not only directly bound Gβγ but also PLCβ2. The binding sites of WDR26 and PLCβ2 on Gβ1γ2 were overlapping but not identical. WDR26 used the same domains for binding Gβγ and PLCβ but still formed a signaling complex with Gβγ and PLCβ2 probably due to the fact that WDR26 formed a higher order oligomer through its Lis homology and C-terminal to LisH (LisH-CTLH) and WD40 domains. Additional studies indicated that the formation of higher order oligomers was required for WDR26 to promote PLCβ2 interaction with and activation by Gβγ. Moreover, WDR26 was required for PLCβ2 translocation from the cytosol to the membrane in polarized leukocytes, and the translocation of PLCβ2 was sufficient to cause partial activation of PLCβ2. Collectively, our data indicate that WDR26 functions as a scaffolding protein to promote PLCβ2 membrane translocation and interaction with Gβγ, thereby enhancing PLCβ2 activation in leukocytes. These findings have identified a novel mechanism of regulating Gβγ signaling through a scaffolding protein.
Background: It remains unclear how Gβγ regulates diverse effectors in cells.
Results: WDR26 exists in oligomers. It simultaneously binds both Gβγ and PLCβ2 to enhance PLCβ2 membrane translocation and activation by Gβγ in leukocytes.
Conclusion: WDR26 functions as a scaffolding protein to promote Gβγ-mediated PLCβ2 activation.
Significance: These findings uncover a novel mechanism of regulating Gβγ signaling through a scaffolding protein.(Video) COVID-19, Immune Function and Strategies for Maintaining Health
Store-operated Ca2+ Entry (SOCE) Induced by Protease-activated Receptor-1 Mediates STIM1 Protein Phosphorylation to Inhibit SOCE in Endothelial Cells through AMP-activated Protein Kinase and p38β Mitogen-activated Protein Kinase
Journal of Biological Chemistry, Volume 288, Issue 23, 2013, pp. 17030-17041
The Ca2+ sensor STIM1 is crucial for activation of store-operated Ca2+ entry (SOCE) through transient receptor potential canonical and Orai channels. STIM1 phosphorylation serves as an “off switch” for SOCE. However, the signaling pathway for STIM1 phosphorylation is unknown. Here, we show that SOCE activates AMP-activated protein kinase (AMPK); its effector p38β mitogen-activated protein kinase (p38β MAPK) phosphorylates STIM1, thus inhibiting SOCE in human lung microvascular endothelial cells. Activation of AMPK using 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) resulted in STIM1 phosphorylation on serine residues and prevented protease-activated receptor-1 (PAR-1)-induced Ca2+ entry. Furthermore, AICAR pretreatment blocked PAR-1-induced increase in the permeability of mouse lung microvessels. Activation of SOCE with thrombin caused phosphorylation of isoform α1 but not α2 of the AMPK catalytic subunit. Moreover, knockdown of AMPKα1 augmented SOCE induced by thrombin. Interestingly, SB203580, a selective inhibitor of p38 MAPK, blocked STIM1 phosphorylation and led to sustained STIM1-puncta formation and Ca2+ entry. Of the three p38 MAPK isoforms expressed in endothelial cells, p38β knockdown prevented PAR-1-mediated STIM1 phosphorylation and potentiated SOCE. In addition, inhibition of the SOCE downstream target CaM kinase kinase β (CaMKKβ) or knockdown of AMPKα1 suppressed PAR-1-mediated phosphorylation of p38β and hence STIM1. Thus, our findings demonstrate that SOCE activates CaMKKβ-AMPKα1-p38β MAPK signaling to phosphorylate STIM1, thereby suppressing endothelial SOCE and permeability responses.
Background: STIM1 is essential for store-operated Ca2+ entry (SOCE) in endothelial cells.
Results: SOCE-activated AMPKα1-p38β signaling phosphorylates STIM1, which in turn inhibits SOCE in endothelial cells.
Conclusion: SOCE-activated signaling pathway completes a negative feedback loop to regulate SOCE in endothelial cells.
Significance: Selective p38β agonists may represent potential therapeutic agents to reverse the vascular leak syndrome.
Copyright © 1965 Published by Elsevier B.V.