Activation of the extracellular signal-regulated kinase by complement C5b-9.
Extracellular signals may be transmitted to nuclear or cytoplasmic effectors via the mitogen-activated protein kinases. In the passive Heymann nephritis (PHN) model of membranous nephropathy, complement C5b-9 induces glomerular epithelial cell (GEC) injury, proteinuria, and activation of phospholipases and protein kinases. This study addresses the complement-mediated activation of the extracellular signal-regulated kinase (ERK). C5b-9 induced ERK threonine202/tyrosine204 phosphorylation (which correlates with activation) in GEC in culture and PHN in vivo. Expression of a dominant-inhibitory mutant of Ras reduced complement-mediated activation of ERK, but activation was not affected significantly by downregulation of protein kinase C. Complement-induced ERK activation resulted in phosphorylation of cytosolic phospholipase A2 and was, in part, responsible for phosphorylation of mitogen-activated protein kinase-associated protein kinase-2, but did not induce phosphorylation of the transcription factor, Elk-1. Activation of ERK was attenuated by drugs that disassemble the actin cytoskeleton (cytochalasin D, latrunculin B), and these compounds interfered with the activation of ERK by mitogen-activated protein kinase kinase (MEK). Overexpression of a constitutively active RhoA as well as inhibition of Rho-associated kinase blocked complement-mediated ERK activation. Complement cytotoxicity was enhanced after disassembly of the actin cytoskeleton but was unaffected after inhibition of complement-induced ERK activation. However, complement cytotoxicity was enhanced in GEC that stably express constitutively active MEK. Thus complement-induced ERK activation depends on cytoskeletal remodelling and affects the regulation of distinct downstream substrates, while chronic, constitutive ERK activation exacerbates complement-mediated GEC injury.
Cybulsky
Andrey V
AV
Department of Medicine, McGill University Health Centre, McGill University, Montreal, Quebec, Canada. andrey.cybulsky@mcgill.ca
Takano
Tomoko
T
Papillon
Joan
J
Bijian
Krikor
K
Guillemette
Julie
J
D000199:Actins / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D015938:Complement Membrane Attack Complex / Q000494:pharmacology*; D003599:Cytoskeleton / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D005921:Glomerulonephritis / Q000276:immunology* / Q000378:metabolism*; D007678:Kidney Glomerulus / Q000166:cytology / Q000201:enzymology* / Q000276:immunology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000276:immunology; D010766:Phosphorylation; D051381:Rats; D018631:ras Proteins / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D015938:Complement Membrane Attack Complex; D048049:Extracellular Signal-Regulated MAP Kinases; D018631:ras Proteins; D020742:rhoA GTP-Binding Protein