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BACKGROUND Soybean is among the ‘big eight’ allergenic foods, and β‐conglycinin, the main antigenic protein of soybean, has high levels of antigenic activity. Why the antigenic activity of soybean β‐conglycinin is not eliminated by enzymatic hydrolysis is not clear. In this study, changes in the molecular composition and antigenicity of β‐conglycinin hydrolyzed by pepsin were analyzed and it was determined whether complete sequential epitopes exist in the resulting hydrolysates. The nature and antigenic activity of protein subunits obtained after β‐conglycinin hydrolysis were also assessed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis and competitive enzyme‐linked immunosorbent assay, respectively. RESULTS The residual antigenic activity of β‐conglycinin was 52%, α′‐ and α‐subunits completely disappeared, the 49 kDa fraction partially disappeared, and peptides measuring 27 and 23 kDa were newly formed after 60 min of enzymatic hydrolysis. Prolonged enzymatic hydrolysis did not result in remarkable changes in these peptides; thus, the peptides show some resistance to enzymatic hydrolysis. The amino acid sequences of the peptide chains were analyzed by matrix‐assisted laser desorption / ionization‐time of flight mass spectrometry and aligned with the related sequences in the corresponding protein and antigen databases. Ten complete sequential epitopes were identified in the residual 49 kDa fraction, of these epitopes, two were from α‐subunits and eight were from β‐subunits. CONCLUSION The presence of complete sequential epitopes in hydrolysates obtained from the enzymatic hydrolysis of soybean is an important reason for the incomplete disappearance of the antigenic activity of β‐conglycinin. © 2020 Society of Chemical Industry

Background Poly-GA, a dipeptide repeat protein unconventionally translated from GGGGCC repeat expansions in C9orf72, is abundant in C9orf72-related amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Although the poly-GA aggregates have been identified in C9orf72-ALS/FTD neurons, the effects on UPS and autophagy, and their exact molecular mechanisms have not been fully elucidated. Results Herein, our in vivo experiments show that ploy-GA mice expressing 150 repeats but not 30 repeats GA exhibit significant aggregates in cells, behavioral deficits, and activate autophagy in the brain. The in vitro results demonstrate that the aggregated poly-GA induce proteasomal stress through directly binding proteasome subunit PSMD2 to recruit proteasome and impair its function, subsequently activate phosphorylation and ubiquitination of p62 to recruit autophagosome, and ultimately leading to compensatory autophagy activation. While rapamycin treatment significantly improves the degenerative symptoms of mice expressing 150 repeats poly-GA, relieves neuronal injury and reduces neuroinflammation and aggregates in the brain. Conclusion In summary, we clarify for the first time the relationship of poly-GA between proteasome and autophagy: poly-GA aggregates recruit autophagosomes only when it forms complex with the proteasome and causes proteasomal stress. Our study provides support for further promoting the comprehension about the pathogenesis of C9orf72 and may bring a hint for the exploration of rapamycin in the treatment of ALS/FTD.