Role of apoptosis signal-regulating kinase 1 in complement-mediated glomerular epithelial cell injury.
In the rat passive Heymann nephritis (PHN) model of membranous nephropathy, complement C5b-9 activates protein kinases in glomerular epithelial cells (GEC), and induces sublethal GEC injury and proteinuria. Complement induces production of reactive oxygen species (ROS) via the NAPDH oxidase, and stimulates phosphorylation of c-Jun N-terminal kinase (JNK) and p38 kinase in a ROS-dependent manner. In the present study, we demonstrate that apoptosis signal-regulating kinase 1 (ASK1) was activated in glomeruli of rats with PHN, and that incubation of GEC in culture with antibody and sublytic C5b-9 stimulated ASK1 activity. The latter was, in part, mediated via the NADPH oxidase and ROS. Sublytic complement induced JNK and p38 phosphorylation, which was amplified in GEC that stably overexpress ASK1, as compared with Neo (control) GEC. Complement-induced lysis was enhanced in GEC that overexpress ASK1, as compared with Neo, and was attenuated in GEC that overexpress a dominant negative ASK1 mutant. Inhibition of p38, but not JNK, attenuated complement lysis in GEC that overexpress ASK1, but not in Neo GEC. In Neo GEC, generation of ROS restricted complement-mediated GEC injury but the protective effect of ROS was lost when ASK1 was overexpressed. We propose that the level of ASK1 expression determines the functional effect of p38 activation, i.e. when ASK1 is overexpressed, p38 activation is amplified, and C5b-9 assembly leads to GEC injury via ASK1 and p38. The present study thus defines a novel role for ASK1 as a mediator of C5b-9-dependent cell injury.
Ren
Guohui
G
Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada.
Huynh
Carl
C
Bijian
Krikor
K
Cybulsky
Andrey V
AV
D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D002478:Cells, Cultured; D015938:Complement Membrane Attack Complex / Q000276:immunology*; D003602:Cytotoxicity, Immunologic; D004721:Endoplasmic Reticulum / Q000201:enzymology / Q000473:pathology; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000201:enzymology* / Q000276:immunology / Q000473:pathology*; D005799:Genes, Dominant; D015433:Glomerulonephritis, Membranous / Q000201:enzymology / Q000276:immunology; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D007678:Kidney Glomerulus / Q000201:enzymology* / Q000276:immunology* / Q000473:pathology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D015854:Up-Regulation / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D015938:Complement Membrane Attack Complex; D018840:HSP70 Heat-Shock Proteins; D007770:L-Lactate Dehydrogenase; D051057:Proto-Oncogene Proteins c-akt; D048031:JNK Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5