Label-free quantitative proteomic analysis reveals strong involvement of complement alternative and terminal pathways in human glomerular sclerotic lesions

Abstract

Since glomerular sclerosis frequently accompanies various glomerular diseases at the end stages, it is challenging to differentiate ubiquitous biological processes underlying this pathology from those critically involved in specific diseases. Furthermore, in-depth proteomic profile of human glomerular sclerosis remains limited. In this study, human glomeruli with intermediate (i-GS) and advanced (GS) sclerotic lesions, which were excluded from specific renal diseases and assumed to be aging-related, were laser captured from macroscopically normal cortex distant from urological carcinoma, and subjected to label-free quantitative proteomic analysis. We explicate an evident increase of membrane attack complex in i-GS and GS with an up-going tendency, which is accompanied by increasing of inhibitory regulators of alternative and terminal pathways. GO annotation and IPA pathway analysis agree to these results. Proteomic findings are validated by immunohistochemical studies which indicate that alternative and terminal pathways are positively involved in the glomerular sclerosis seen in distinct renal diseases. Furthermore, proteomic analysis also demonstrates remarkable increases of complement factor B in GS and TGF-ß1 in both GS and i-GS. Identification of complement factor B implicates that on-site activation of alternative pathway may occur in injured glomeruli and stepwise increase of TGF-ß1 suggests its contribution to the progression of glomerulosclerosis. Biological significanceThis study provides in-depth quantitative proteomic profiles of human glomeruli with intermediate and advanced sclerotic lesions. It reveals that the over-expression of alternative and terminal pathway components is significantly involved in human glomerulosclerosis seen in distinct renal diseases. Proteomic identification of the increased TGF-ß1 provides supporting evidence for the role of podocyte apoptosis leading to human glomerulosclerosis.