The WERA cancer center matrix: Strategic management of patient access to precision oncology in a large and mostly rural area of Germany.

PURPOSE: Providing patient access to precision oncology (PO) is a major challenge of clinical oncologists. Here, we provide an easily transferable model from strategic management science to assess the outreach of a cancer center. METHODS: As members of the German WERA alliance, the cancer centers in Würzburg, Erlangen, Regensburg and Augsburg merged care data regarding their geographical impact. Specifically, we examined the provenance of patients from WERA´s molecular tumor boards (MTBs) between 2020 and 2022 (n = 2243). As second dimension, we added the provenance of patients receiving general cancer care by WERA. Clustering our catchment area along these two dimensions set up a four-quadrant matrix consisting of postal code areas with referrals towards WERA. These areas were re-identified on a map of the Federal State of Bavaria. RESULTS: The WERA matrix overlooked an active screening area of 821 postal code areas - representing about 50 % of Bavaria´s spatial expansion and more than six million inhabitants. The WERA matrix identified regions successfully connected to our outreach structures in terms of subsidiarity - with general cancer care mainly performed locally but PO performed in collaboration with WERA. We also detected postal code areas with a potential PO backlog - characterized by high levels of cancer care performed by WERA and low levels or no MTB representation. CONCLUSIONS: The WERA matrix provided a transparent portfolio of postal code areas, which helped assessing the geographical impact of our PO program. We believe that its intuitive principle can easily be transferred to other cancer centers.

Individualized targeted treatment in a case of a rare TFG::ROS1 fusion positive inflammatory myofibroblastic tumor (IMT).

BACKGROUND: Inflammatory myofibroblastic tumor (IMTs) are rare mesenchymal neoplasms with slow growth. Resection is considered as therapeutic standard, with chemotherapy being insufficiently effective in advanced disease. ALK translocations are present in 50% of cases, ROS1 fusions (YWHAE::ROS1, TFG::ROS1) are extremely rare. Here, we present a case with TFG::ROS1 fusion and highlight the significance of molecular tumor boards (MTBs) in clinical precision oncology for post-last-line therapy. CASE PRESENTATION: A 32-year-old woman presented with IMT diagnosed at age 27 for biopsy and treatment evaluation. Previous treatments included multiple resections and systemic therapy with vinblastine, cyclophosphamide, and methotrexate. A computed tomography scan showed extensive tumor infiltration of the psoas muscles and the posterior abdomen. Next generation sequencing revealed an actionable ROS1 fusion (TFG::ROS1) with breakpoints at exon 4/35 including the kinase domain and activating the RAS-pathway. TFG, the Trk-fused gene, exerts functions such as intracellular trafficking and exhibits high sequence homology between species. Based on single reports about efficacy of ROS1-targeting in ROS1 translocation positive IMTs the patient was started on crizotinib, an ATP-competitive small molecule c-MET, ALK and ROS1-inhibitor. With a follow-up of more than 9 months, the patient continues to show a profound response with major tumor regression, improved quality of life and no evidence for severe adverse events. CONCLUSION: This case underscores the importance of the availability of modern molecular diagnostics and interdisciplinarity in precision oncology to identify rare, disease-defining genotypes that make an otherwise difficult-to-treat disease targetable.

Probing the E1o-E2o and E1a-E2o Interactions in Binary Subcomplexes of the Human 2-Oxoglutarate Dehydrogenase and 2-Oxoadipate Dehydrogenase Complexes by Chemical Cross-Linking Mass Spectrometry and Molecular Dynamics Simulation.

The human 2-oxoglutarate dehydrogenase complex (hOGDHc) is a key enzyme in the tricarboxylic acid cycle and is one of the main regulators of mitochondrial metabolism through NADH and reactive oxygen species levels. Evidence was obtained for formation of a hybrid complex between the hOGDHc and its homologue the 2-oxoadipate dehydrogenase complex (hOADHc) in the L-lysine metabolic pathway, suggesting a crosstalk between the two distinct pathways. Findings raised fundamental questions about the assembly of hE1a (2-oxoadipate-dependent E1 component) and hE1o (2-oxoglutarate-dependent E1) to the common hE2o core component. Here we report chemical cross-linking mass spectrometry (CL-MS) and molecular dynamics (MD) simulation analyses to understand assembly in binary subcomplexes. The CL-MS studies revealed the most prominent loci for hE1o-hE2o and hE1a-hE2o interactions and suggested different binding modes. The MD simulation studies led to the following conclusions: (i) The N-terminal regions in E1s are shielded by, but do not interact directly with hE2o. (ii) The hE2o linker region exhibits the highest number of H-bonds with the N-terminus and α/ß1 helix of hE1o, yet with the interdomain linker and α/ß1 helix of hE1a. (iii) The C-termini are involved in dynamic interactions in complexes, suggesting the presence of at least two conformations in solution.

Alterations in Natural Killer Cells in Colorectal Cancer Patients with Stroma AReactive Invasion Front Areas (SARIFA).

BACKGROUND: Recently, our group introduced Stroma AReactive Invasion Front Areas (SARIFA) as an independent prognostic predictor for a poorer outcome in colon cancer patients, which is probably based on immunologic alterations combined with a direct tumor-adipocyte interaction: the two together reflecting a distinct tumor biology. Considering it is already known that peripheral immune cells are altered in colorectal cancer (CRC) patients, this study aims to investigate the changes in lymphocyte subsets in SARIFA-positive cases and correlate these changes with the local immune response. METHODS: Flow cytometry was performed to analyze B, T, and natural killer (NK) cells in the peripheral blood (PB) of 45 CRC patients. Consecutively, lymphocytes in PB, tumor-infiltrating lymphocytes (TILs), and CD56+ and CD57+ lymphocytes at the invasion front and the tumor center were compared between patients with SARIFA-positive and SARIFA-negative CRCs. RESULTS: Whereas no differences could be observed regarding most PB lymphocyte populations as well as TILs, NK cells were dramatically reduced in the PB of SARIFA-positive cases. Moreover, CD56 and CD57 immunohistochemistry suggested SARIFA-status-dependent changes regarding NK cells and NK-like lymphocytes in the tumor microenvironment. CONCLUSION: This study proves that our newly introduced biomarker, SARIFA, comes along with distinct immunologic alterations, especially regarding NK cells.

Identification of Disparities in Personalized Cancer Care-A Joint Approach of the German WERA Consortium.

(1) Background: molecular tumor boards (MTBs) are crucial instruments for discussing and allocating targeted therapies to suitable cancer patients based on genetic findings. Currently, limited evidence is available regarding the regional impact and the outreach component of MTBs; (2) Methods: we analyzed MTB patient data from four neighboring Bavarian tertiary care oncology centers in Würzburg, Erlangen, Regensburg, and Augsburg, together constituting the WERA Alliance. Absolute patient numbers and regional distribution across the WERA-wide catchment area were weighted with local population densities; (3) Results: the highest MTB patient numbers were found close to the four cancer centers. However, peaks in absolute patient numbers were also detected in more distant and rural areas. Moreover, weighting absolute numbers with local population density allowed for identifying so-called white spots-regions within our catchment that were relatively underrepresented in WERA MTBs; (4) Conclusions: investigating patient data from four neighboring cancer centers, we comprehensively assessed the regional impact of our MTBs. The results confirmed the success of existing collaborative structures with our regional partners. Additionally, our results help identifying potential white spots in providing precision oncology and help establishing a joint WERA-wide outreach strategy.

Structures of the Most Twisted Thioamide and Selenoamide: Effect of Higher Chalcogens of Twisted Amides on N-C(X) Resonance.

Amide bond replacement with planar isosteric chalcogen analogues has an important implication for the properties of the N-C(X) linkage in structural chemistry, biochemistry and organic synthesis. Herein, we report the first higher chalcogen derivatives of non-planar twisted amides. The synthesis of twisted thioamide in a versatile system has been accomplished by direct thionation without cleavage of the σ N-C bond. The synthesis of twisted selenoamide has been accomplished by selenation with Woollins' reagent. The structures of higher chalcogen analogues of non-planar amides were unambiguously confirmed by X-ray crystallography. Reactivity studies were conducted to determine the effect of isologous N-C(O) to N-C(X) replacement on the properties of the amide linkage. Computational studies were employed to evaluate structural and energetic parameters of amide bond alteration in higher chalcogen amides. The study provides the first experimental evidence on the effect of chalcogen isologues on the structural and electronic properties of the non-planar amide N-C(X) linkage.

Functional Versatility of the Human 2-Oxoadipate Dehydrogenase in the L-Lysine Degradation Pathway toward Its Non-Cognate Substrate 2-Oxopimelic Acid.

The human 2-oxoadipate dehydrogenase complex (OADHc) in L-lysine catabolism is involved in the oxidative decarboxylation of 2-oxoadipate (OA) to glutaryl-CoA and NADH (+H+). Genetic findings have linked the DHTKD1 encoding 2-oxoadipate dehydrogenase (E1a), the first component of the OADHc, to pathogenesis of AMOXAD, eosinophilic esophagitis (EoE), and several neurodegenerative diseases. A multipronged approach, including circular dichroism spectroscopy, Fourier Transform Mass Spectrometry, and computational approaches, was applied to provide novel insight into the mechanism and functional versatility of the OADHc. The results demonstrate that E1a oxidizes a non-cognate substrate 2-oxopimelate (OP) as well as OA through the decarboxylation step, but the OADHc was 100-times less effective in reactions producing adipoyl-CoA and NADH from the dihydrolipoamide succinyltransferase (E2o) and dihydrolipoamide dehydrogenase (E3). The results revealed that the E2o is capable of producing succinyl-CoA, glutaryl-CoA, and adipoyl-CoA. The important conclusions are the identification of: (i) the functional promiscuity of E1a and (ii) the ability of the E2o to form acyl-CoA products derived from homologous 2-oxo acids with five, six, and even seven carbon atoms. The findings add to our understanding of both the OADHc function in the L-lysine degradative pathway and of the molecular mechanisms leading to the pathogenesis associated with DHTKD1 variants.

Restoring Immune Mediated Disease Control by Ipilimumab Re-exposition in a Heavily pretreated Patient With MSI-H mCRC.

BACKGROUND: Immune-Checkpoint-inhibitors (ICIs) are approved in first line therapy of microsatellite-instable, deficient miss-match-repair (MSI-H-dMMR) metastatic colorectal cancer (mCRC), and in second line after standard chemotherapy. Evidence supporting immunotherapy after immunotherapy is scarce. CASE REPORT: This case report highlights the course of a heavily pretreated patient with MSI-H mCRC with progression after multiple local therapies, standard chemotherapies and pembrolizumab. After 4 cycles of ipilimumab and nivolumab followed by nivolumab-maintenance he achieved a long-lasting disease control of 22 months. After further subsequent progression he regained immune mediated disease control by a second "boost" of ipilimumab. CONCLUSION: Re-exposition with ipilimumab is a potential option to restore immune-mediated-disease-control in patients with preceding long-lasting response to ipilimumab/nivolumab and with dMMR-tumors. The clinical situation of progress after long-lasting disease control on ICIs becomes more common and is an opportunity to investigate potential strategies for restoring immune mediated disease control.

E. coli and the etiology of human PBC: Antimitochondrial antibodies and spreading determinants.

BACKGROUND AND AIMS: The increased frequency of urinary tract infections in patients with primary biliary cholangitis (PBC) and the cross-reactivity between the lipoyl domains (LD) of human pyruvate dehydrogenase complex (hPDC-E2) and Escherichia coli PDC-E2 (ePDC-E2) have long suggested a role of E. coli in causality of PBC. This issue, however, has remained speculative. We hypothesized that by generating specific constructs of human and E. coli PDC-E2, we would be able to assess the specificity of autoantibody responses and define whether exposure to E. coli in susceptible hosts is the basis for the antimitochondrial antibody (AMA) response. APPROACH AND RESULTS: Importantly, the reactivity of hPDC-E2 LD (hPDC-E2LD) affinity-purified antibodies against hPDC-E2LD could only be removed by prior absorption with hPDC-E2LD and not ePDC-E2, suggesting the presence of unique human PDC-E2 epitopes distinct from E. coli PDC-E2. To identify the autoepitope(s) present in hPDC-E2LD, a more detailed study using a variety of PDC-E2 constructs was tested, including the effect of lipoic acid (LA) on ePDC-E2 conformation and AMA recognition. Individual recombinant ePDCE2 LD domains LD1, LD2 and LD3 did not react with either AMA or antibodies to LA (anti-LA), but in contrast, anti-LA was readily reactive against purified recombinant LD1, LD2, and LD3 expressed in tandem (LP); such reactivity increased when LP was precultured with LA. Moreover, when the three LD (LD1, LD2, LD3) domains were expressed in tandem in pET28a or when LD1 was expressed in another plasmid pGEX, they were lipoylated and reactive to PBC sera. CONCLUSIONS: In conclusion, our data are consistent with an exposure to E. coli that elicits specific antibody to ePDC-E2 resulting in determinant spreading and the classic autoantibody to hPDC-E2LD. We argue this is the first step to development of human PBC.

A Retrospective 5-Year Single Center Study Highlighting the Risk of Cancer Predisposition in Adolescents and Young Adults.

The knowledge of inherited cancer susceptibility opens a new field of cancer medicine. We conducted a retrospective single-center cohort study. Data of AYA cancer patients registered between January 2014 and December 2018 were analyzed. The median age at cancer diagnosis of 704 patients (343 males, 361 females) was 32 years (range, 15-39 years), median follow-up was 181 days (range, 1-1975 days). Solid tumors were diagnosed in 575 (81.7%) patients, hematologic malignancies in 129 (18.3%) patients. Multiple primary cancers were reported in 36 (5.1%) patients. Malignancies that may be indicators of inherited cancer susceptibility were diagnosed in 2.6% of patients with cancers of the endocrine system, in 73% of cancers of the gastrointestinal system, in 88% of tumors of the central nervous system, in 92% of cancers of the urinary tract, and in 59% of head and neck tumors. In addition, all patients with breast cancer, sarcoma, and peripheral nerve sheath tumor were in need of genetic counselling. In sum, at least 181 of 704 (25.7%) AYA cancer patients presented with malignancies suspicious of harboring pathogenic germline variants. Evaluation of AYA cancer patients for hereditary cancer predisposition needs to be integrated into daily practice.

Toward an Understanding of the Structural and Mechanistic Aspects of Protein-Protein Interactions in 2-Oxoacid Dehydrogenase Complexes.

The 2-oxoglutarate dehydrogenase complex (OGDHc) is a key enzyme in the tricarboxylic acid (TCA) cycle and represents one of the major regulators of mitochondrial metabolism through NADH and reactive oxygen species levels. The OGDHc impacts cell metabolic and cell signaling pathways through the coupling of 2-oxoglutarate metabolism to gene transcription related to tumor cell proliferation and aging. DHTKD1 is a gene encoding 2-oxoadipate dehydrogenase (E1a), which functions in the L-lysine degradation pathway. The potentially damaging variants in DHTKD1 have been associated to the (neuro) pathogenesis of several diseases. Evidence was obtained for the formation of a hybrid complex between the OGDHc and E1a, suggesting a potential cross talk between the two metabolic pathways and raising fundamental questions about their assembly. Here we reviewed the recent findings and advances in understanding of protein-protein interactions in OGDHc and 2-oxoadipate dehydrogenase complex (OADHc), an understanding that will create a scaffold to help design approaches to mitigate the effects of diseases associated with dysfunction of the TCA cycle or lysine degradation. A combination of biochemical, biophysical and structural approaches such as chemical cross-linking MS and cryo-EM appears particularly promising to provide vital information for the assembly of 2-oxoacid dehydrogenase complexes, their function and regulation.

Structure of the dihydrolipoamide succinyltransferase (E2) component of the human alpha-ketoglutarate dehydrogenase complex (hKGDHc) revealed by cryo-EM and cross-linking mass spectrometry: Implications for the overall hKGDHc structure.

BACKGROUND: The human mitochondrial alpha-ketoglutarate dehydrogenase complex (hKGDHc) converts KG to succinyl-CoA and NADH. Malfunction of and reactive oxygen species generation by the hKGDHc as well as its E1-E2 subcomplex are implicated in neurodegenerative disorders, ischemia-reperfusion injury, E3-deficiency and cancers. METHODS: We performed cryo-EM, cross-linking mass spectrometry (CL-MS) and molecular modeling analyses to determine the structure of the E2 component of the hKGDHc (hE2k); hE2k transfers a succinyl group to CoA and forms the structural core of hKGDHc. We also assessed the overall structure of the hKGDHc by negative-stain EM and modeling. RESULTS: We report the 2.9 Šresolution cryo-EM structure of the hE2k component. The cryo-EM map comprises density for hE2k residues 151-386 - the entire (inner) core catalytic domain plus a few additional residues -, while residues 1-150 are not observed due to the inherent flexibility of the N-terminal region. The structure of the latter segment was also determined by CL-MS and homology modeling. Negative-stain EM on in vitro assembled hKGDHc and previous data were used to build a putative overall structural model of the hKGDHc. CONCLUSIONS: The E2 core of the hKGDHc is composed of 24 hE2k chains organized in octahedral (8 × 3 type) assembly. Each lipoyl domain is oriented towards the core domain of an adjacent chain in the hE2k homotrimer. hE1k and hE3 are most likely tethered at the edges and faces, respectively, of the cubic hE2k assembly. GENERAL SIGNIFICANCE: The revealed structural information will support the future pharmacologically targeting of the hKGDHc.

Inhibition and Crystal Structure of the Human DHTKD1-Thiamin Diphosphate Complex.

DHTKD1 is the E1 component of the 2-oxoadipate dehydrogenase complex, which is an enzyme involved in the catabolism of (hydroxy-)lysine and tryptophan. Mutations in DHTKD1 have been associated with 2-aminoadipic and 2-oxoadipic aciduria, Charcot-Marie-Tooth disease type 2Q and eosinophilic esophagitis, but the pathophysiology of these clinically distinct disorders remains elusive. Here, we report the identification of adipoylphosphonic acid and tenatoprazole as DHTKD1 inhibitors using targeted and high throughput screening, respectively. We furthermore elucidate the DHTKD1 crystal structure with thiamin diphosphate bound at 2.25 Å. We also report the impact of 10 disease-associated missense mutations on DHTKD1. Whereas the majority of the DHTKD1 variants displayed impaired folding or reduced thermal stability in combination with absent or reduced enzyme activity, three variants showed no abnormalities. Our work provides chemical and structural tools for further understanding of the function of DHTKD1 and its role in several human pathologies.

Structure-function analyses of the G729R 2-oxoadipate dehydrogenase genetic variant associated with a disorder of l-lysine metabolism.

2-Oxoadipate dehydrogenase (E1a, also known as DHTKD1, dehydrogenase E1, and transketolase domain-containing protein 1) is a thiamin diphosphate-dependent enzyme and part of the 2-oxoadipate dehydrogenase complex (OADHc) in l-lysine catabolism. Genetic findings have linked mutations in the DHTKD1 gene to several metabolic disorders. These include α-aminoadipic and α-ketoadipic aciduria (AMOXAD), a rare disorder of l-lysine, l-hydroxylysine, and l-tryptophan catabolism, associated with clinical presentations such as developmental delay, mild-to-severe intellectual disability, ataxia, epilepsy, and behavioral disorders that cannot currently be managed by available treatments. A heterozygous missense mutation, c.2185G→A (p.G729R), in DHTKD1 has been identified in most AMOXAD cases. Here, we report that the G729R E1a variant when assembled into OADHc in vitro displays a 50-fold decrease in catalytic efficiency for NADH production and a significantly reduced rate of glutaryl-CoA production by dihydrolipoamide succinyl-transferase (E2o). However, the G729R E1a substitution did not affect any of the three side-reactions associated solely with G729R E1a, prompting us to determine the structure-function effects of this mutation. A multipronged systematic analysis of the reaction rates in the OADHc pathway, supplemented with results from chemical cross-linking and hydrogen-deuterium exchange MS, revealed that the c.2185G→A DHTKD1 mutation affects E1a-E2o assembly, leading to impaired channeling of OADHc intermediates. Cross-linking between the C-terminal region of both E1a and G729R E1a with the E2o lipoyl and core domains suggested that correct positioning of the C-terminal E1a region is essential for the intermediate channeling. These findings may inform the development of interventions to counter the effects of pathogenic DHTKD1 mutations.

DHTKD1 and OGDH display substrate overlap in cultured cells and form a hybrid 2-oxo acid dehydrogenase complex in vivo.

Glutaric aciduria type 1 (GA1) is an inborn error of lysine degradation characterized by a specific encephalopathy that is caused by toxic accumulation of lysine degradation intermediates. Substrate reduction through inhibition of DHTKD1, an enzyme upstream of the defective glutaryl-CoA dehydrogenase, has been investigated as a potential therapy, but revealed the existence of an alternative enzymatic source of glutaryl-CoA. Here, we show that loss of DHTKD1 in glutaryl-CoA dehydrogenase-deficient HEK-293 cells leads to a 2-fold decrease in the established GA1 clinical biomarker glutarylcarnitine and demonstrate that oxoglutarate dehydrogenase (OGDH) is responsible for this remaining glutarylcarnitine production. We furthermore show that DHTKD1 interacts with OGDH, dihydrolipoyl succinyltransferase and dihydrolipoamide dehydrogenase to form a hybrid 2-oxoglutaric and 2-oxoadipic acid dehydrogenase complex. In summary, 2-oxoadipic acid is a substrate for DHTKD1, but also for OGDH in a cell model system. The classical 2-oxoglutaric dehydrogenase complex can exist as a previously undiscovered hybrid containing DHTKD1 displaying improved kinetics towards 2-oxoadipic acid.

Exclusive neuronal detection of KGDHC-specific subunits in the adult human brain cortex despite pancellular protein lysine succinylation.

The ketoglutarate dehydrogenase complex (KGDHC) consists of three different subunits encoded by OGDH (or OGDHL), DLST, and DLD, combined in different stoichiometries. DLD subunit is shared between KGDHC and pyruvate dehydrogenase complex, branched-chain alpha-keto acid dehydrogenase complex, and the glycine cleavage system. Despite KGDHC's implication in neurodegenerative diseases, cell-specific localization of its subunits in the adult human brain has never been investigated. Here, we show that immunoreactivity of all known isoforms of OGDHL, OGDH, and DLST was detected exclusively in neurons of surgical human cortical tissue samples identified by their morphology and visualized by double labeling with fluorescent Nissl, while being absent from glia expressing GFAP, Aldhl1, myelin basic protein, Olig2, or IBA1. In contrast, DLD immunoreactivity was evident in both neurons and glia. Specificity of anti-KGDHC subunits antisera was verified by a decrease in staining of siRNA-treated human cancer cell lines directed against the respective coding gene products; furthermore, immunoreactivity of KGDHC subunits in human fibroblasts co-localized > 99% with mitotracker orange, while western blotting of 63 post-mortem brain samples and purified recombinant proteins afforded further assurance regarding antisera monospecificity. KGDHC subunit immunoreactivity correlated with data from the Human Protein Atlas as well as RNA-Seq data from the Allen Brain Atlas corresponding to genes coding for KGDHC components. Protein lysine succinylation, however, was immunohistochemically evident in all cortical cells; this was unexpected, because this posttranslational modification requires succinyl-CoA, the product of KGDHC. In view of the fact that glia of the human brain cortex lack succinate-CoA ligase, an enzyme producing succinyl-CoA when operating in reverse, protein lysine succinylation in these cells must exclusively rely on propionate and/or ketone body metabolism or some other yet to be discovered pathway encompassing succinyl-CoA.

Active Site Histidines Link Conformational Dynamics with Catalysis on Anti-Infective Target 1-Deoxy-d-xylulose 5-Phosphate Synthase.

The product of 1-deoxy-d-xyluose 5-phosphate (DXP) synthase, DXP, feeds into the bacterial biosynthesis of isoprenoids, thiamin diphosphate (ThDP), and pyridoxal phosphate. DXP is essential for human pathogens but not utilized by humans; thus, DXP synthase is an attractive anti-infective target. The unique ThDP-dependent mechanism and structure of DXP synthase offer ideal opportunities for selective targeting. Upon reaction with pyruvate, DXP synthase uniquely stabilizes the predecarboxylation intermediate, C2α-lactylThDP (LThDP), in a closed conformation. Subsequent binding of d-glyceraldehyde 3-phosphate induces an open conformation that is proposed to destabilize LThDP, triggering decarboxylation. Evidence for the closed and open conformations has been revealed by hydrogen-deuterium exchange mass spectrometry and X-ray crystallography, which indicate that H49 and H299 are involved in conformational dynamics and movement of the fork and spoon motifs away from the active site is important for the closed-to-open transition. Interestingly, H49 and H299 are critical for DXP formation and interact with the predecarboxylation intermediate in the closed conformation. H299 is removed from the active site in the open conformation of the postdecarboxylation state. In this study, we show that substitution at H49 and H299 negatively impacts LThDP formation by shifting the conformational equilibrium of DXP synthase toward an open conformation. We also present a method for monitoring the dynamics of the spoon motif that uncovered a previously undetected role for H49 in coordinating the closed conformation. Overall, our results suggest that H49 and H299 are critical for the closed, predecarboxylation state providing the first direct link between catalysis and conformational dynamics.

Underlying molecular alterations in human dihydrolipoamide dehydrogenase deficiency revealed by structural analyses of disease-causing enzyme variants.

Human dihydrolipoamide dehydrogenase (hLADH, hE3) deficiency (OMIM# 246900) is an often prematurely lethal genetic disease usually caused by inactive or partially inactive hE3 variants. Here we report the crystal structure of wild-type hE3 at an unprecedented high resolution of 1.75 Å and the structures of six disease-causing hE3 variants at resolutions ranging from 1.44 to 2.34 Å. P453L proved to be the most deleterious substitution in structure as aberrations extensively compromised the active site. The most prevalent G194C-hE3 variant primarily exhibited structural alterations close to the substitution site, whereas the nearby cofactor-binding residues were left unperturbed. The G426E substitution mainly interfered with the local charge distribution introducing dynamics to the substitution site in the dimer interface; G194C and G426E both led to minor structural changes. The R460G, R447G and I445M substitutions all perturbed a solvent accessible channel, the so-called H+/H2O channel, leading to the active site. Molecular pathomechanisms of enhanced reactive oxygen species (ROS) generation and impaired binding to multienzyme complexes were also addressed according to the structural data for the relevant mutations. In summary, we present here for the first time a comprehensive study that links three-dimensional structures of disease-causing hE3 variants to residual hLADH activities, altered capacities for ROS generation, compromised affinities for multienzyme complexes and eventually clinical symptoms. Our results may serve as useful starting points for future therapeutic intervention approaches.

Human 2-Oxoglutarate Dehydrogenase and 2-Oxoadipate Dehydrogenase Both Generate Superoxide/H2O2 in a Side Reaction and Each Could Contribute to Oxidative Stress in Mitochondria.

According to recent findings, the human 2-oxoglutarate dehydrogenase complex (hOGDHc) could be an important source of the reactive oxygen species in the mitochondria and could contribute to mitochondrial abnormalities associated with multiple neurodegenerative diseases, including Alzheimer's disease, Huntington disease, and Parkinson's disease. The human 2-oxoadipate dehydrogenase (hE1a) is a novel protein, which is encoded by the DHTKD1 gene. Both missence and nonsense mutations were identified in the DHTKD1 that lead to alpha-aminoadipic and alpha-oxoadipic aciduria, a metabolic disorder with a wide variety of the neurological abnormalities, and Charcot-Marie-Tooth disease type 2Q, an inherited neurological disorder affecting the peripheral nervous system. Recently, the rare pathogenic mutations in DHTKD1 and an increased H2O2 production were linked to the genetic ethiology of Eosinophilic Esophagitis (EoE), a chronic allergic inflammatory esophageal disorder. In view of the importance of hOGDHc in the tricarboxylic acid cycle (TCA cycle) and hE1a on the L-lysine, L-hydroxylysine and L-tryptophan degradation pathway in mitochondria, and to enhance our current understanding of the mechanism of superoxide/H2O2 generation by hOGDHc, and by human 2-oxoadipate dehydrogenase complex (hOADHc), this review focuses on several novel and unanticipated recent findings in vitro that emerged from the Jordan group's research. Most significantly, the hE1o and hE1a now join the hE3 as being able to generate the superoxide/H2O2 in mitochondria.

A multipronged approach unravels unprecedented protein-protein interactions in the human 2-oxoglutarate dehydrogenase multienzyme complex.

The human 2-oxoglutaric acid dehydrogenase complex (hOGDHc) plays a pivotal role in the tricarboxylic acid (TCA) cycle, and its diminished activity is associated with neurodegenerative diseases. The hOGDHc comprises three components, hE1o, hE2o, and hE3, and we recently reported functionally active E1o and E2o components, enabling studies on their assembly. No atomic-resolution structure for the hE2o component is currently available, so here we first studied the interactions in the binary subcomplexes (hE1o-hE2o, hE1o-hE3, and hE2o-hE3) to gain insight into the strength of their interactions and to identify the interaction loci in them. We carried out multiple physico-chemical studies, including fluorescence, hydrogen-deuterium exchange MS (HDX-MS), and chemical cross-linking MS (CL-MS). Our fluorescence studies suggested a strong interaction for the hE1o-hE2o subcomplex, but a much weaker interaction in the hE1o-hE3 subcomplex, and failed to identify any interaction in the hE2o-hE3 subcomplex. The HDX-MS studies gave evidence for interactions in the hE1o-hE2o and hE1o-hE3 subcomplexes comprising full-length components, identifying: (i) the N-terminal region of hE1o, in particular the two peptides 18YVEEM22 and 27ENPKSVHKSWDIF39 as constituting the binding region responsible for the assembly of the hE1o with both the hE2o and hE3 components into hOGDHc, an hE1 region absent in available X-ray structures; and (ii) a novel hE2o region comprising residues from both a linker region and from the catalytic domain as being a critical region interacting with hE1o. The CL-MS identified the loci in the hE1o and hE2o components interacting with each other.