Role of Lipoylation of the Immunodominant Epitope of Pyruvate Dehydrogenase Complex: Toward a Peptide-Based Diagnostic Assay for Primary Biliary Cirrhosis

Abstract

Primary biliary cirrhosis is an immune-mediated chronic liver disease whose diagnosis relies on the detection of serum antimitochondrial antibodies directed against a complex set of proteins, among which pyruvate dehydrogenase complex is considered the main autoantigen. We studied the immunological role of the lipoyl domain of this protein using synthetic lipoylated peptides, showing that the lipoyl chain chirality does not affect autoantibody recognition and, most importantly, confirming that both lipoylated and unlipoylated peptides are able to recognize specific autoantibodies in patients sera. In fact, 74% of patients sera recognize at least one of the tested peptides but very few positive sera recognized exclusively the lipoylated peptide, suggesting that the lipoamide moiety plays a marginal role within the autoreactive epitope. These results are supported by a conformational analysis showing that the lipoyl moiety of pyruvate dehydrogenase complex appears to be involved in hydrophobic interactions, which may limit its exposition and thus its contribution to the complex antigenic epitope. A preliminary analysis of the specificity of the two most active peptides indicates that they could be part of a panel of synthetic antigens collectively able to mimic in a simple immunoenzymatic assay the complex positivity pattern detected in immunofluorescence.

Cuproptosis key gene FDX1 is a prognostic biomarker and associated with immune infiltration in glioma

“…(D) The relationship between FDX1 and receptor genes expression in glioma. Frontiers in Medicine 11 frontiersin.org key genes by bioinformatics analysis, comparing the co-expression gene of FDX1 in gliomas with with an additional 6 lipoacylation-related genes (79)(80)(81)(82). The key genes were subjected to intersection analysis and expression correlation analysis, to screen and identify potential Cuproptosis process genes through co-expression network research methods.…”

“…Recent blockbuster reports have found that FDX1, a key regulator of Cuproposis, regulates cell death by influencing fatty protein lipoylation. To further explore the role of FDX1 in gliomas, we attempted to identify potential Cuproptosis key genes by bioinformatics analysis, comparing the co-expression gene of FDX1 in gliomas with with an additional 6 lipoacylation-related genes ( 79 – 82 ). The key genes were subjected to intersection analysis and expression correlation analysis, to screen and identify potential Cuproptosis process genes through co-expression network research methods.…”

Study of Aberrant Modifications in Peptides as a Test Bench to Investigate the Immunological Response to Non-Enzymatic Glycation

“…Sera from 27 TD1 and 29 NBD subjects were tested by SP-ELISA using the synthetic peptides 1 and 2. The applied ELISA protocol for detection of IgM and IgG antibodies against [(deoxyFru)Lys 173 ]PDC-E2(167-186)-KKKK and [(deoxyFru)Lys 7 ]CSF114 antigens was previously developed and applied routinely in our laboratory for [Lys 173 ]PDC-E2(167-186)-KKKK and [Lys 7 ] CSF114 antigens (Lolli et al 2005a;Pacini et al 2015;Nuti et al 2018). The obtained IgM and IgG data distribution is reported in Fig.…”

“…We previously proposed to use peptides as synthetic antigens for efficient detection, including the aforementioned chemical modifications in the strategic positions in selected sequences. In particular, we employed CSF114 as an optimally designed β-turn conformation, and the PDC-E2(167-186) fragment, which is a mitochondrial protein component of the pyruvate dehydrogenase complex (Lolli et al 2005b;Pacini et al 2015;Nuti et al 2018).…”

“…It has been previously successfully demonstrated that synthetic peptides exposing an aberrant PTM are valid tools to detect antibodies in autoimmune diseases, like in primary biliary cirrhosis and multiple sclerosis (Lolli et al, 2005a,b;Pacini et al, 2015;Walvoort et al, 2016;Nuti et al, 2018). These tools can be generated by the so-called 'chemical reverse approach' (CRA), based on the use of patient sera to screen focused libraries of synthetic modified peptides.…”