TY - JOUR A1 - McNulty, Margaret A. A1 - Goupil, Brad A. A1 - Albarado, Diana C. A1 - Castaño-Martinez, Teresa A1 - Ambrosi, Thomas H. A1 - Puh, Spela A1 - Schulz, Tim Julius A1 - Schürmann, Annette A1 - Morrison, Christopher D. A1 - Laeger, Thomas T1 - FGF21, not GCN2, influences bone morphology due to dietary protein restrictions JF - Bone Reports N2 - Background: Dietary protein restriction is emerging as an alternative approach to treat obesity and glucose intolerance because it markedly increases plasma fibroblast growth factor 21 (FGF21) concentrations. Similarly, dietary restriction of methionine is known to mimic metabolic effects of energy and protein restriction with FGF21 as a required mechanism. However, dietary protein has been shown to be required for normal bone growth, though there is conflicting evidence as to the influence of dietary protein restriction on bone remodeling. The purpose of the current study was to evaluate the effect of dietary protein and methionine restriction on bone in lean and obese mice, and clarify whether FGF21 and general control nonderepressible 2 (GCN2) kinase, that are part of a novel endocrine pathway implicated in the detection of protein restriction, influence the effect of dietary protein restriction on bone. Methods: Adult wild-type (WT) or Fgf21 KO mice were fed a normal protein (18 kcal%; CON) or low protein (4 kcal%; LP) diet for 2 or 27 weeks. In addition, adult WT or Gcn2 KO mice were fed a CON or LP diet for 27 weeks. Young New Zealand obese (NZO) mice were placed on high-fat diets that provided protein at control (16 kcal%; CON), low levels (4 kcal%) in a high-carbohydrate (LP/HC) or high-fat (LP/HF) regimen, or on high-fat diets (protein, 16 kcal%) that provided methionine at control (0.86%; CON-MR) or low levels (0.17%; MR) for up to 9 weeks. Long bones from the hind limbs of these mice were collected and evaluated with micro-computed tomography (mu CT) for changes in trabecular and cortical architecture and mass. Results: In WT mice the 27-week LP diet significantly reduced cortical bone, and this effect was enhanced by deletion of Fgf21 but not Gcn2. This decrease in bone did not appear after 2 weeks on the LP diet. In addition, Fgf21 KO mice had significantly less bone than their WT counterparts. In obese NZO mice dietary protein and methionine restriction altered bone architecture. The changes were mediated by FGF21 due to methionine restriction in the presence of cystine, which did not increase plasma FGF21 levels and did not affect bone architecture. Conclusions: This study provides direct evidence of a reduction in bone following long-term dietary protein restriction in a mouse model, effects that appear to be mediated by FGF21. KW - dietary restriction KW - protein restriction KW - FGF21 KW - GCN2 KW - microcomputed tomography Y1 - 2020 U6 - https://doi.org/10.1016/j.bonr.2019.100241 SN - 2352-1872 VL - 12 SP - 1 EP - 10 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schjeide, Brit-Maren A1 - Schenke, Maren A1 - Seeger, Bettina A1 - Püschel, Gerhard T1 - Validation of a novel double control quantitative copy number PCR method to quantify off-target transgene integration after CRISPR-induced DNA modification JF - Methods and protocols : M&Ps N2 - In order to improve a recently established cell-based assay to assess the potency of botulinum neurotoxin, neuroblastoma-derived SiMa cells and induced pluripotent stem-cells (iPSC) were modified to incorporate the coding sequence of a reporter luciferase into a genetic safe harbor utilizing CRISPR/Cas9. A novel method, the double-control quantitative copy number PCR (dc-qcnPCR), was developed to detect off-target integrations of donor DNA. The donor DNA insertion success rate and targeted insertion success rate were analyzed in clones of each cell type. The dc-qcnPCR reliably quantified the copy number in both cell lines. The probability of incorrect donor DNA integration was significantly increased in SiMa cells in comparison to the iPSCs. This can possibly be explained by the lower bundled relative gene expression of a number of double-strand repair genes (BRCA1, DNA2, EXO1, MCPH1, MRE11, and RAD51) in SiMa clones than in iPSC clones. The dc-qcnPCR offers an efficient and cost-effective method to detect off-target CRISPR/Cas9-induced donor DNA integrations. KW - CRISPR editing validation KW - copy number analyses KW - homology-directed repair KW - homologous recombination deficiency Y1 - 2022 U6 - https://doi.org/10.3390/mps5030043 SN - 2409-9279 VL - 5 IS - 3 SP - 1 EP - 14 PB - MDPI CY - Basel, Schweiz ER - TY - JOUR A1 - Rund, Katharina M. A1 - Heylmann, Daniel A1 - Seiwert, Nina A1 - Wecklein, Sabine A1 - Oger, Camille A1 - Galano, Jean-Marie A1 - Durand, Thierry A1 - Chen, Rongjun A1 - Güler, Faikah A1 - Fahrer, Jörg A1 - Bornhorst, Julia A1 - Schebb, Nils Helge T1 - Formation of trans-epoxy fatty acids correlates with formation of isoprostanes and could serve as biomarker of oxidative stress JF - Prostaglandins & Other Lipid Mediators N2 - In mammals, epoxy-polyunsaturated fatty acids (epoxy-PUFA) are enzymatically formed from naturally occurring all-cis PUFA by cytochrome P450 monooxygenases leading to the generation of cis-epoxy-PUFA (mixture of R,S- and S,R-enantiomers). In addition, also non-enzymatic chemical peroxidation gives rise to epoxy-PUFA leading to both, cis- and trans-epoxy-PUFA (mixture of R,R- and S,S-enantiomers). Here, we investigated for the first time trans-epoxy-PUFA and the trans/cis-epoxy-PUFA ratio as potential new biomarker of lipid peroxidation. Their formation was analyzed in correlation with the formation of isoprostanes (IsoP), which are commonly used as biomarkers of oxidative stress. Five oxidative stress models were investigated including incubations of three human cell lines as well as the in vivo model Caenorhabditis elegans with tert-butyl hydroperoxide (t-BOOH) and analysis of murine kidney tissue after renal ischemia reperfusion injury (IRI). A comprehensive set of IsoP and epoxy-PUFA derived from biologically relevant PUFA (ARA, EPA and DHA) was simultaneously quantified by LC-ESI(-)-MS/MS. Following renal IRI only a moderate increase in the kidney levels of IsoP and no relevant change in the trans/cis-epoxy-PUFA ratio was observed. In all investigated cell lines (HCT-116, HepG2 and Caki-2) as well as C. elegans a dose dependent increase of both, IsoP and the trans/cis-epoxy-PUFA ratio in response to the applied t-BOOH was observed. The different cell lines showed a distinct time dependent pattern consistent for both classes of autoxidatively formed oxylipins. Clear and highly significant correlations of the trans/cisepoxy-PUFA ratios with the IsoP levels were found in all investigated cell lines and C. elegans. Based on this, we suggest the trans/cis-epoxy-PUFA ratio as potential new biomarker of oxidative stress, which warrants further investigation. KW - Isoprostane KW - Trans-epoxy-fatty acid KW - Oxidative stress KW - Biomarker KW - Oxylipin KW - Eicosanoid Y1 - 2019 U6 - https://doi.org/10.1016/j.prostaglandins.2019.04.004 SN - 1098-8823 SN - 2212-196X VL - 144 PB - Elsevier CY - New York ER - TY - JOUR A1 - Rohn, Isabelle A1 - Kroepfl, Nina A1 - Bornhorst, Julia A1 - Kühnelt, Doris A1 - Schwerdtle, Tanja T1 - Side-directed transfer and presystemic metabolism of selenoneine in a human intestinal barrier model JF - Molecular nutrition & food research : bioactivity, chemistry, immunology, microbiology, safety, technology N2 - Scope: Selenoneine, a recently discovered selenium (Se) species mainly present in marine fish, is the Se analogue of ergothioneine, a sulfur-containing purported antioxidant. Although similar properties have been proposed for selenoneine, data on its relevance to human health are yet scarce. Here, the transfer and presystemic metabolism of selenoneine in an in vitro model of the human intestinal barrier are investigated. Methods and results: Selenoneine and the reference species Se-methylselenocysteine (MeSeCys) and selenite are applied to the Caco-2 intestinal barrier model. Selenoneine is transferred in higher amounts, but with similar kinetics as selenite, while MeSeCys shows the highest permeability. In contrast to the reference species, transfer of selenoneine is directed toward the blood side. Cellular Se contents demonstrate that selenoneine is efficiently taken up by Caco-2 cells. Moreover, HPLC/MS-based Se speciation studies reveal a partial metabolism to Se-methylselenoneine, a metabolite previously detected in human blood and urine. Conclusions: Selenoneine is likely to pass the intestinal barrier via transcellular, carrier-mediated transport, is highly bioavailable to Caco-2 cells and undergoes metabolic transformations. Therefore, further studies are needed to elucidate its possible health effects and to characterize the metabolism of selenoneine in humans. KW - bioavailability KW - Caco-2 intestinal barrier model KW - presystemic metabolism KW - selenoneine KW - Se-methylselenoneine Y1 - 2019 U6 - https://doi.org/10.1002/mnfr.201900080 SN - 1613-4125 SN - 1613-4133 VL - 63 IS - 12 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Winkelbeiner, Nicola Lisa A1 - Wandt, Viktoria Klara Veronika A1 - Ebert, Franziska A1 - Lossow, Kristina A1 - Bankoglu, Ezgi E. A1 - Martin, Maximilian A1 - Mangerich, Aswin A1 - Stopper, Helga A1 - Bornhorst, Julia A1 - Kipp, Anna Patricia A1 - Schwerdtle, Tanja T1 - A Multi-Endpoint Approach to Base Excision Repair Incision Activity Augmented by PARylation and DNA Damage Levels in Mice BT - Impact of Sex and Age JF - International Journal of Molecular Sciences N2 - Investigation of processes that contribute to the maintenance of genomic stability is one crucial factor in the attempt to understand mechanisms that facilitate ageing. The DNA damage response (DDR) and DNA repair mechanisms are crucial to safeguard the integrity of DNA and to prevent accumulation of persistent DNA damage. Among them, base excision repair (BER) plays a decisive role. BER is the major repair pathway for small oxidative base modifications and apurinic/apyrimidinic (AP) sites. We established a highly sensitive non-radioactive assay to measure BER incision activity in murine liver samples. Incision activity can be assessed towards the three DNA lesions 8-oxo-2’-deoxyguanosine (8-oxodG), 5-hydroxy-2’-deoxyuracil (5-OHdU), and an AP site analogue. We applied the established assay to murine livers of adult and old mice of both sexes. Furthermore, poly(ADP-ribosyl)ation (PARylation) was assessed, which is an important determinant in DDR and BER. Additionally, DNA damage levels were measured to examine the overall damage levels. No impact of ageing on the investigated endpoints in liver tissue were found. However, animal sex seems to be a significant impact factor, as evident by sex-dependent alterations in all endpoints investigated. Moreover, our results revealed interrelationships between the investigated endpoints indicative for the synergetic mode of action of the cellular DNA integrity maintaining machinery. KW - maintenance of genomic integrity KW - ageing KW - sex KW - DNA damage KW - base excision repair (incision activity) KW - DNA damage response KW - poly(ADP-ribosyl)ation KW - liver Y1 - 2020 U6 - https://doi.org/10.3390/ijms21186600 SN - 1422-0067 VL - 21 IS - 18 PB - Molecular Diversity Preservation International CY - Basel ER - TY - JOUR A1 - Baesler, Jessica A1 - Kopp, Johannes Florian A1 - Pohl, Gabriele A1 - Aschner, Michael A1 - Haase, Hajo A1 - Schwerdtle, Tanja A1 - Bornhorst, Julia T1 - Zn homeostasis in genetic models of Parkinson’s disease in Caenorhabditis elegans JF - Journal of Trace Elements in Medicine and Biology N2 - While the underlying mechanisms of Parkinson’s disease (PD) are still insufficiently studied, a complex interaction between genetic and environmental factors is emphasized. Nevertheless, the role of the essential trace element zinc (Zn) in this regard remains controversial. In this study we altered Zn balance within PD models of the versatile model organism Caenorhabditis elegans (C. elegans) in order to examine whether a genetic predisposition in selected genes with relevance for PD affects Zn homeostasis. Protein-bound and labile Zn species act in various areas, such as enzymatic catalysis, protein stabilization pathways and cell signaling. Therefore, total Zn and labile Zn were quantitatively determined in living nematodes as individual biomarkers of Zn uptake and bioavailability with inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) or a multi-well method using the fluorescent probe ZinPyr-1. Young and middle-aged deletion mutants of catp-6 and pdr-1, which are orthologues of mammalian ATP13A2 (PARK9) and parkin (PARK2), showed altered Zn homeostasis following Zn exposure compared to wildtype worms. Furthermore, age-specific differences in Zn uptake were observed in wildtype worms for total as well as labile Zn species. These data emphasize the importance of differentiation between Zn species as meaningful biomarkers of Zn uptake as well as the need for further studies investigating the role of dysregulated Zn homeostasis in the etiology of PD. KW - Caenorhabditis elegans KW - Zinc KW - Zinc homeostasis KW - Parkinson disease KW - Labile zinc Y1 - 2019 U6 - https://doi.org/10.1016/j.jtemb.2019.05.005 VL - 55 SP - 44 EP - 49 PB - Elsevier CY - München ER - TY - JOUR A1 - Wardelmann, Kristina T1 - Hormonal regulation of neuronal mitochondrial unfolded protein response and its impact on metabolism N2 - The hypothalamus is the main brain area of central regulation of whole body metabolism through impacting food intake and energy expenditure. For the complex regulation, high amounts of energy are needed and mainly provided by mitochondria. Hence, mitochondrial function is crucial for cell homeostasis and modulates central insulin sensitivity. Thus, mitochondrial dysfunction is associated with insulin resistance in the brain and therefore is involved in the pathogenesis of type-2 diabetes (T2D). Mitochondrial health and protein homeostasis is propagated by mitochondrial stress responses like e.g. mitochondrial unfolded protein response (UPRmt). Therefore, studies regarding the regulation of mitochondrial homeostasis are crucial for understanding its effects on the central nervous system (CNS) for the progression of metabolic and nutrition-dependent disorders. One main aim of this thesis was to investigate the metabolic regulation of mitochondrial stress responsiveness in the hypothalamus. The observed results showed that functional ERK-dependent insulin signaling is needed for regulation of mitochondrial stress response (MSR) genes and positively impacted the metabolism by controlling mitochondrial proteostasis without affecting mitochondrial biogenesis. To further explore the role of MSR genes for brain cell homeostasis and its consequences for the metabolism, one of the key players - the mitochondrial chaperone heat shock protein 10 (Hsp10) – was studied in detail. Hsp10 expression was decreased in insulin-resistant, hyperglycemic db/db mice brains along with increased protein oxidation. Leptin, another key hormone in regulating metabolism, was able to induce Hsp10 in neurons. Appropriately, lentiviral-mediated knock down (KD) of Hsp10 introduced into hypothalamic CLU-183 cells induced mitochondrial dysfunction, altered mitochondrial dynamics and increased contact sites between mitochondria and endoplasmic reticulum (ER). In addition, Hsp10 KD caused cellular insulin resistance along with increasing oxidative stress specifically in mitochondrial fraction. Interestingly, acute Hsp10 KD in the arcuate nucleus of the hypothalamus in C57BL/6N male mice did not change body weight or food intake, but it increased plasma leptin concentrations suggesting an effect on global leptin signaling. It increased hepatic markers of gluconeogenesis and hepatic insulin resistance along with features of low-grade inflammation. Long-term studies of hypothalamic Hsp10 KD mice revealed unaltered systemic insulin sensitivity. The demonstrated increase in markers of hepatic gluconeogenesis of acute Hsp10 KD was still exhibited after 13 weeks, but insulin resistance in the liver was no longer observed. In conclusion, hypothalamic insulin action regulates MSR and ensures proper mitochondrial function which positively affects metabolism. In addition, hypothalamic Hsp10 acts as a modulator of both insulin and leptin signaling and is identified as pivotal for the regulation of central mitochondrial function as well as insulin sensitivity in the brain and it impacts liver function. It may present a regulator of brain-liver crosstalk influencing hepatic gluconeogenesis and insulin sensitivity through a novel regulatory signaling mechanism. N2 - Die zentrale Regulation des Metabolismus wird vom Hypothalamus gesteuert, indem diese Hirnregion die Nahrungsaufnahme sowie den Energieverbrauch reguliert. Dieser komplexe Regulations-Mechanismus benötigt eine enorme Menge an Energie, die hauptsächlich von Mitochondrien produziert wird. Somit ist die mitochondriale Funktion existenziell für die Zell-Homöostase und in einigen Studien konnte gezeigt werden, dass diese Funktion ebenfalls mit der zentralen Insulin-Sensitivität zusammenhängt. Mitochondriale Dysfunktion hingegen ist mit Insulin-Resistenz im Gehirn assoziiert und damit an der Pathogenese und Progression von Diabetes Typ 2 beteiligt. Mitochondriale Stressantworten wie zum Beispiel die mitochondriale ungefaltete Proteinantwort (mitochondrial unfolded stress response) ermöglichen die Protein-Homöostase und einwandfreie Funktion der Mitochondrien. Folglich sind Untersuchungen der Regulation der mitochondrialen Funktion von großer Bedeutung für das Verständnis der zentralnervösen Auswirkungen auf die Entwicklung ernährungsbedingter Störungen des Metabolismus. Eine der Zielstellungen dieser Doktorarbeit war die Untersuchung der metabolischen Regulation der hypothalamische Stressantwort der Mitochondrien. Die hier durchgeführten Studien zeigten, dass die funktionelle Insulin Signalkaskade für die Regulierung der mitochondrialen Stressantwort (MSR) benötigt wird und dies durch die Kontrolle der Proteostase der Mitochondrien positive Effekte auf den Metabolismus hat. Zur genaueren Klärung der Aufgabe der mitochondrialen Stressantwort für die Homöostase der Gehirnzelle und dessen Auswirkungen für den Metabolismus wurde eines der Mitglieder dieser Stressantwort, das mitochondriale Chaperon Hitzeschock-Protein 10 (Hsp10), näher untersucht. Zunächst konnte dargelegt werden, dass die Expression von Hsp10 in Gehirnen von Insulin-resistenten, hyperglykämischen db/db Mäusen verringert ist. Diese Mäuse zeigen zusätzlich eine Erhöhung der Oxidation von Proteinen im Gehirn, ein weiteres Merkmal des Krankheitsbildes von Diabetes Typ 2. Darüber hinaus zeigten die vorliegenden Studien, dass Leptin, ein weiteres für die Regulation des Metabolismus wichtiges Hormon, die Expression von Hsp10 in Neuronen induzieren konnte. Der lentiviral-vermittelte knockdown von Hsp10 in der hypothalamischen, neuronalen Zelllinie CLU 183 hingegen verursacht mitochondriale Dysfunktion, sowie eine veränderte mitochondriale Dynamik einhergehend mit erhöhtem Kontakt von Mitochondrien mit dem endoplasmatischen Retikulum. Zusätzlich wurde Mitochondrien-spezifischer oxidativer Stress von der Reduzierung von Hsp10 verursacht und eine Insulin-Resistenz ausgelöst. Interessanterweise beeinflusste der akute knockdown der Hsp10 Expression im Nucleus Arcuatus des Hypothalamus in männlichen C57BL/6N Mäusen weder das Körpergewicht noch die Futteraufnahme, jedoch war die Plasma-Konzentration von Leptin erhöht. Dies deutet auf einen Effekt von zentralem Hsp10 auf die systemische Leptin-Signalwirkung hin. Außerdem wurde durch die akute Verringerung von hypothalamischen Hsp10 PEPCK in der Leber induziert, ein wichtiges Protein der Gluconeogenese, sowie eine hepatische Insulin-Resistenz ausgelöst, verbunden mit Anzeichen einer schwachen Inflammation dieses Gewebes. Bei verlängerter Reduktion der Expression von Hsp10 im Hypothalamus wurde die systemische Insulin-Sensitivität der Mäuse nicht verändert. Die hepatische Insulin-Resistenz war nach 13 Wochen des hypothalamischen knockdown von Hsp10 in C57BL/6N Mäusen nicht mehr zu beobachten, aber die Induktion des Gluconeogenese-Gens PEPCK in der Leber war weiterhin existent. Zusammenfassend zeigt diese Dissertation, dass die hypothalamische Insulin-Signalwirkung die mitochondriale Stressantwort reguliert und somit die Funktion der Mitochondrien gewährleistet, was den Metabolismus positiv beeinflusst. Des Weiteren deuten die diskutierten Ergebnisse darauf hin, dass Hsp10 im Hypothalamus ein Modulator der Insulin- sowie Leptinsignalwirkung des Körpers ist. Hsp10 ist entscheidend für die Regulierung der zentralen Funktion der Mitochondrien sowie der Insulin-Sensitivität in Gehirn und beeinflusst die Leberfunktion. Die Konsequenzen der Verringerung von Hsp10 im Hypothalamus modulieren die hepatische Gluconeogenese und Insulin-Sensitivität. Daraus folgend wird Hsp10 als neuer Regulator der Kommunikation zwischen Gehirn und Leber identifiziert, mit einem in diesem Falle noch unbekannten Mechanismus der Signalweiterleitung zwischen den beiden Organen. Y1 - 2019 ER - TY - JOUR A1 - Christakoudi, Sofa A1 - Tsilidis, Konstantinos K. A1 - Muller, David C. A1 - Freisling, Heinz A1 - Weiderpass, Elisabete A1 - Overvad, Kim A1 - Söderberg, Stefan A1 - Häggström, Christel A1 - Pischon, Tobias A1 - Dahm, Christina C. A1 - Zhang, Jie A1 - Tjønneland, Anne A1 - Schulze, Matthias Bernd T1 - A Body Shape Index (ABSI) achieves better mortality risk stratification than alternative indices of abdominal obesity: results from a large European cohort JF - Scientific Reports N2 - Abdominal and general adiposity are independently associated with mortality, but there is no consensus on how best to assess abdominal adiposity. We compared the ability of alternative waist indices to complement body mass index (BMI) when assessing all-cause mortality. We used data from 352,985 participants in the European Prospective Investigation into Cancer and Nutrition (EPIC) and Cox proportional hazards models adjusted for other risk factors. During a mean follow-up of 16.1 years, 38,178 participants died. Combining in one model BMI and a strongly correlated waist index altered the association patterns with mortality, to a predominantly negative association for BMI and a stronger positive association for the waist index, while combining BMI with the uncorrelated A Body Shape Index (ABSI) preserved the association patterns. Sex-specific cohort-wide quartiles of waist indices correlated with BMI could not separate high-risk from low-risk individuals within underweight (BMI<18.5 kg/m(2)) or obese (BMI30 kg/m(2)) categories, while the highest quartile of ABSI separated 18-39% of the individuals within each BMI category, which had 22-55% higher risk of death. In conclusion, only a waist index independent of BMI by design, such as ABSI, complements BMI and enables efficient risk stratification, which could facilitate personalisation of screening, treatment and monitoring. KW - all-cause mortality KW - anthropometric measures KW - mass index KW - overweight KW - cancer KW - prediction KW - adiposity KW - size Y1 - 2020 VL - 10 IS - 1 PB - Springer Nature CY - Berlin ER - TY - JOUR A1 - Castro, Jose Pedro A1 - Fernando, Raquel A1 - Reeg, Sandra A1 - Meinl, Walter A1 - Almeida, Henrique A1 - Grune, Tilman T1 - Non-enzymatic cleavage of Hsp90 by oxidative stress leads to actin aggregate formation BT - A novel gain-of-function mechanism JF - Redox Biology N2 - Aging is accompanied by the accumulation of oxidized proteins. To remove them, cells employ the proteasomal and autophagy-lysosomal systems; however, if the clearance rate is inferior to its formation, protein aggregates form as a hallmark of proteostasis loss. In cells, during stress conditions, actin aggregates accumulate leading to impaired proliferation and reduced proteasomal activity, as observed in cellular senescence. The heat shock protein 90 (Hsp90) is a molecular chaperone that binds and protects the proteasome from oxidative inactivation. We hypothesized that in oxidative stress conditions a malfunction of Hsp90 occurs resulting in the aforementioned protein aggregates. Here, we demonstrate that upon oxidative stress Hsp90 loses its function in a highly specific non-enzymatic iron-catalyzed oxidation event and its breakdown product, a cleaved form of Hsp90 (Hsp90cl), acquires a new function in mediating the accumulation of actin aggregates. Moreover, the prevention of Hsp90 cleavage reduces oxidized actin accumulation, whereas transfection of the cleaved form of Hsp90 leads to an enhanced accumulation of oxidized actin. This indicates a clear role of the Hsp90cl in the aggregation of oxidized proteins. KW - Oxidative stress KW - Protein oxidation KW - Heat shock protein 90 KW - Proteasome KW - Protein aggregates Y1 - 2019 U6 - https://doi.org/10.1016/j.redox.2019.101108 SN - 2213-2317 VL - 21 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Raupbach, Jana A1 - Ott, Christiane A1 - König, Jeannette A1 - Grune, Tilman T1 - Proteasomal degradation of glycated proteins depends on substrate unfolding: Preferred degradation of moderately modified myoglobin JF - Free radical biology and medicine : the official journal of the Oxygen Society, a constituent member of the International Society for Free Radical Research N2 - The Maillard reaction generates protein modifications which can accumulate during hyperglycemia or aging and may have inflammatory consequences. The proteasome is one of the major intracellular systems involved in the proteolytic degradation of modified proteins but its role in the degradation of glycated proteins is scarcely studied. In this study, chemical and structural changes of glycated myoglobin were analyzed and its degradation by 20S proteasome was studied. Myoglobin was incubated with physiological (5-10 mM), moderate (50-100 mM) and severe levels (300 mM) of glucose or methylglyoxal (MGO, 50 mM). Glycation increased myoglobin's fluorescence and surface hydrophobicity. Severe glycation generated crosslinked proteins as shown by gel electrophoresis. The concentration of advanced glycation endproducts (AGEs) N-epsilon-carboxymethyl lysine (CML), N-epsilon-carboxyethyl lysine (CEL), methylglyoxal-derived hydroimidazolone-1 (MG-H1), pentosidine and pyrraline was analyzed after enzymatic hydrolysis followed by UPLC-MS/MS. Higher concentrations of glucose increased all analyzed AGEs and incubation with MGO led to a pronounced increase of CEL and MG-H1. The binding of the heme group to apo-myoglobin was decreased with increasing glycation indicating the loss of tertiary protein structure. Proteasomal degradation of modified myoglobin compared to native myoglobin depends on the degree of glycation: physiological conditions decreased proteasomal degradation whereas moderate glycation increased degradation. Severe glycation again decreased proteolytic cleavage which might be due to crosslinking of protein monomers. The activity of the proteasomal subunit beta 5 is influenced by the presence of glycated myoglobin. In conclusion, the role of the proteasome in the degradation of glycated proteins is highly dependent on the level of glycation and consequent protein unfolding. KW - Glycation KW - Myoglobin KW - Heme KW - Advanced glycation endproducts KW - 20S KW - proteasome Y1 - 2020 U6 - https://doi.org/10.1016/j.freeradbiomed.2019.11.024 SN - 0891-5849 SN - 1873-4596 VL - 152 SP - 516 EP - 524 PB - Elsevier CY - New York ER -