REPOSITORY > RESULTS

Abstract

Protein phosphorylation is an important post-translational modification in cellular signal transmission. Perturbations in this mechanism can cause phenotypic abnormalities in organisms. Legumain, also known as asparagine-specific endopeptidase, is a cysteine proteinase found in plants and animals. Legumain regulates renal and haematopoietic homeostasis, as well as immunological responses. Its dysregulation is linked to a variety of malignancies and neurological disorders. Legumain knockout mice have a normal phenotype with the exception of impaired kidney function, hemophagocytic syndrome, and extramedullary haematopoiesis. In this work, we examined alterations in protein phosphorylation in legumain knock-out mice compared to wild-type controls to better understand how legumain deficiency impacts protein phosphorylation and associated cell signalling. Phosphopeptides from kidney and liver tissues were enriched and analysed using mass spectrometry, then verified using western blot and immunohistochemistry. We identified multiple differentially phosphorylated sites between wild type and legumain knock out mice. Among them, Y-box binding protein 1, an RNA and DNA binding protein was found to be differentially phosphorylated on three sites. In legumain-knockout mice kidneys as well as on HL-60 human cell line model of legumain knock out, a key location on the serine 100 residue of Y-box binding protein 1 activates the NF-κB pathway, leading to an increased inflammatory response. This was corroborated by increased expression of NF-κB genes and their downstream targets. Overall, this work sheds light on the role of legumain in mice and its effects on several cellular processes.