Project description:Cross-linking mass spectrometry has developed into an important method to study protein structures and interactions. The in-solution cross-linking workflows involve time and sample consuming steps and do not provide sensible solutions for differentiating cross-links obtained from co-occurring protein oligomers, complexes, or conformers. Here we developed a cross-linking workflow combining blue native PAGE with in-gel cross-linking mass spectrometry (IGX-MS). This workflow circumvents steps, such as buffer exchange and cross-linker concentration optimization. Additionally, IGX-MS enables the parallel analysis of co-occurring protein complexes using only small amounts of sample. Another benefit of IGX-MS observed by experiments on GroEL and purified bovine heart mitochondria, is the substantial reduction of artificial over-length cross-links when compared to in-solution cross-linking. We next used IGX-MS to investigate the complement components C5, C6, and their hetero-dimeric C5b6 complex. The obtained cross-links were used to generate a refined structural model of the complement component C6, resembling C6 in its inactivated state. This finding shows that IGX-MS can be used to provide new insights into the initial stages of the terminal complement pathway.
Project description:Cardiovascular diseases are a major cause of life-threatening burden around the world. The heart has a very low regeneration capacity and donor organs for transplantation are scarce. Therefore regeneration of lost myocardium with stem cell-derived cardiomyocytes (CMs) provides an attractive strategy for heart repair. Human pluripotent stem cells (hPSCs) can be efficiently differentiated in vitro into CMs but the molecular mechanisms behind this process are still not fully understood. In particular identification of secreted autocrine and/or paracrine factors that function as important extrinsic signals remained elusive because the mass spectrometry (MS)-based identification of secreted proteins from cell culture supernatants is impeded by high levels of albumin present in common differentiation media. Thus we established an albumin-free cardiomyogenic differentiation medium and performed secretomics at seven different time points during in vitro differentiation. This analysis led to the identification of 4832 proteins with 1802 being significantly altered during differentiation and 431 of these were annotated as secreted according to gene ontology. Bioinformatics revealed enrichment of extrinsic Wnt pathway-related proteins 3 days upon induction of differentiation and of extracellular matrix proteins in the resulting CMs. Numerous extrinsic components of Wnt, Activin A, Nodal, TGFβ, BMP or FGF signaling pathways were quantitatively assessed during differentiation. Notably, the abundance of pathway agonists was generally lower compared to the respective antagonists but their curves of progression over timer were rather similar. We hypothesize that Activin A, Nodal and TGFβ signaling are turned down shortly upon initiation of cardiac differentiation whereas BMP signaling is switched on. Wnt and FGF signaling peaks between d0 and d3 of differentiation and interestingly, Activin A and TGFβ signaling seem to be reactivated at the cardiac progenitor stages and/or in early CMs.
Project description:Acute myeloid leukemia (AML) in children with cytogenetic aberrations like translocation t(7;12)(q36;p13) is associated with inferior outcome. The translocation can lead to a fusion transcript MNX1::ETV6 but also to activation of MNX1 transcription. We generated an AML mouse model by transplantation of fetal liver cells with ectopic expression of MNX1. AML was highly penetrant in immunocompromised and less penetrant in immunocompetent mice. Transforming capacity was restricted to fetal liver cells and could not achieved with adult bone marrow cells, in concordance with the clinical finding that t(7;12)(q36;p13) is mostly restricted to infants. Ectopic expression of MNX1 led to increased H3K4methylation and reduced H3K27me3, possibly through its interaction with methyl transferases. MNX1 expression was accompanied with changes in genome wide chromatin accessibility , increased DNA damage, depletion in the LSK population and skewing toward the myeloid lineage. These effects, together with leukemia development, could be prevented by the S-adenosylmethionine analogue Sinefungin that acts as a SAM competitor and a pan methyltranferases inhibitor. Expression profiles of a human iPSC AML model with t(7;12) and of TARGET pediatric AML and TCGA patients support the rationale for targeting MNX1 and downstream pathways.
Project description:Chickpea (Cicer arietinum L.) seed proteins show a lot of functional properties leading this leg-ume an interesting component for the development of protein-enriched foods. However, both in-depth proteomic investigation and structural characterization of chickpea proteins seed are still lacking. In this paper we report a detailed characterization of chickpea seed protein fraction by means SDS-PAGE, in-gel protein digestion, high-resolution mass spectrometry, and database searching. By this approach twenty SDS gel bands were cut and analysed. While the majority of bands and the identified peptides were related to vicilin and legumin storage proteins, also metabolic functional proteins were detected. Legumins, as expected, were revealed at 45÷65 kDa, as whole subunits with the α- and β-chains linked together by a disulphide bond, but also at lower mass ranges (α- and β-chains migrating alone). Similarly, but not expected, also the vi-cilins were spread along the mass region between 65 and 23 kDa, with some of them identified in several bands. In-depth MS structural characterization allowed to determine that, although chickpea vicilins were always described as proteins lacking of cysteine residues, they contain this amino acid residue. Moreover, similarly to legumins, these storage proteins are firstly syn-thesized as pre-propolypeptides (Mr 50÷80 kDa), that may undergo to proteolytic steps that cut not only the signal peptides but also produce different subunits having lower molecular masses. Overall, about 360 different proteins specific of the Cicer arietinum L. species were identified and characterized, a result that up to date represents the most detailed description of seed’s proteome of this legume.
Project description:Candida glabrata is a common opportunistic fungal pathogen of humans, with the emergence of resitant strains being of particulary concern. The cell wall associated and secretory proteins are intrinsically involved in vital functions during the fungal-host interactions. These proteins are responsible for eliciting immune response in host during candidiasis and therefore can be a promising candidates for vaccine development. BALB/c mice were broadly divided into unimmunized, immunized groups and the designated groups were immunized with β-mercaptoethanol (β-ME) call wall extract, and secretory protein extract from C. glabrata via intraperitoneal route. All the animals were then challenged with a lethal dose of C. glabrata. Furthermore, we applied a liquid chromatography-tandem mass spectrometry (LC–MS/MS) -based approach for the characterization of β-ME extract and secretory protein extract from C. glabrata, which resulted in a comprehensive cell wall and secretory proteome map.portunistic fungal pathogen of humans, with the emergence of resitant strains being of particulary concern. The cell wall associated and secretory proteins are intrinsically involved in vital functions during the fungal-host interactions. These proteins are responsible for eliciting immune response in host during candidiasis and therefore can be a promising candidates for vaccine development. BALB/c mice were broadly divided into unimmunized, immunized groups and the designated groups were immunized with β-mercaptoethanol (β-ME) call wall extract, and secretory protein extract from C. glabrata via intraperitoneal route. All the animals were then challenged with a lethal dose of C. glabrata. Furthermore, we applied a liquid chromatography-tandem mass spectrometry (LC–MS/MS) -based approach for the characterization of β-ME extract and secretory protein extract from C. glabrata, which resulted in a comprehensive cell wall and secretory proteome map.
Project description:Small molecule inhibitors of glycosylation enzymes are valuable tools for dissecting glycan functions and potential drug candidates. Screening for inhibitors of glycosyltransferases are mainly performed by in vitro enzyme assays with difficulties moving candidates to cells and animals. Here, we circumvent this by employing a cell-based screening assay using glycoengineered cells expressing tailored reporter glycoproteins. We focused on GalNAc-type O-glycosylation, and selected the GalNAc-T11 isoenzyme that selectively glycosylates the endocytic low density lipoprotein receptor (LDLR)-related proteins as target. Our screen of a limited small molecule compound library did not identify selective inhibitors of GalNAc-T11, however we identified two compounds that broadly inhibited Golgi-localized glycosylation processes. These compounds mediated reversible fragmentation of the Golgi system without affecting secretion. We demonstrate how these inhibitors can be used to manipulate glycosylation in cells to induce expression of truncated O-glycans and augment binding of cancer-specific Tn-glycoprotein antibodies and to inhibit expression of heparan sulfate and binding and infection of SARS-CoV-2.
Project description:A wide range of protein acyl modifications has been identified on enzymes across various metabolic processes; however, the impact of these modifications remains poorly understood. Protein glutarylation is a recently identified modification that can be non-enzymatically driven by glutaryl-CoA. In mammalian systems, this unique metabolite is only produced in the lysine and tryptophan oxidative pathways. To better understand the biology of protein glutarylation, we studied the relationship between enzymes within the lysine/tryptophan catabolic pathways, protein glutarylation, and regulation by the deglutarylating enzyme Sirtuin 5 (SIRT5). Here, we identify glutarylation of the lysine oxidation pathway enzyme glutaryl-CoA dehydrogenase (GCDH). We show increased GCDH glutarylation when glutaryl-CoA production is stimulated by lysine catabolism. Our data reveal glutarylation of GCDH impacts its function, ultimately decreasing lysine oxidation. We then demonstrate the ability of SIRT5 to deglutarylate GCDH, restoring its enzymatic activity. Finally, metabolomic and bioinformatic data indicate a novel role for SIRT5 in regulation of amino acid metabolism. Together, these data suggest a model whereby a feedback loop exists within the lysine/tryptophan oxidation pathway, in which glutaryl-CoA is produced, in turn inhibiting GCDH function. This inhibition is relieved by SIRT5 deacylation activity.
Project description:This project aims to understand better the stress response mechanisms of components of the well known High Osmolarity Glycerol two-component regulatory system in the model organism Magnaporthe oryzae. Currently, two putative isoforms of the transfer protein YPD1 (MGG_07173) are described as theoretical proteins in the UniProt database (G4MTL0 and G4MTK9). For better understanding of signal transduction and response triggering we aimed to identify alternative isoforms that might explain the variety of triggered responses throughout the YPD1 signal transfer hub.
Project description:B. kashiwanohense PV20-2 and B. pseudolongum PV8-2 are strains isolated from breast fed iron deficient Kenyan infants, selected for their high iron sequestration mechanisms and their genome was completely sequenced. Based on their high iron sequestration features we hypothesized that B. kashiwanohense PV20-2 and B. pseudolongum PV8-2, possess iron related genes and excrete iron binding proteins in the culture media under iron limited conditions. Thus, the complete genomes of B. kashiwanohense PV20-2 and B. pseudolongum PV8-2 were compared to other bifidobacterial genomes to identify genes potentially involved in iron metabolism and the coding sequences from the genome were used as a scaffold to identify the extracellular proteome of both strains grown under low iron conditions using a gel-based shotgun proteomic approach.
Project description:B. kashiwanohense PV20-2 and B. pseudolongum PV8-2 are strains isolated from breast fed iron deficient Kenyan infants, selected for their high iron sequestration mechanisms and their genome was completely sequenced. Based on their high iron sequestration features we hypothesized that B. kashiwanohense PV20-2 and B. pseudolongum PV8-2, possess iron related genes and excrete iron binding proteins in the culture media under iron limited conditions. Thus, the complete genomes of B. kashiwanohense PV20-2 and B. pseudolongum PV8-2 were compared to other bifidobacterial genomes to identify genes potentially involved in iron metabolism and the coding sequences from the genome were used as a scaffold to identify the extracellular proteome of both strains grown under low iron conditions using a gel-based shotgun proteomic approach.