Complement C5b-9 membrane attack complex increases expression of endoplasmic reticulum stress proteins in glomerular epithelial cells.
In the passive Heymann nephritis (PHN) model of membranous nephropathy, complement C5b-9 induces glomerular epithelial cell (GEC) injury, proteinuria, and activation of cytosolic phospholipase A(2) (cPLA(2)). This study addresses the role of endoplasmic reticulum (ER) stress proteins (bip, grp94) in GEC injury. GEC that overexpress cPLA(2) (produced by transfection) and "neo" GEC (which expresses cPLA(2) at a lower level) were incubated with complement (40 min), and leakage of constitutively expressed bip and grp94 from ER into cytosol was measured to monitor ER injury. Greater leakage of bip and grp94 occurred in complement-treated GEC that overexpress cPLA(2), as compared with neo, implying that cPLA(2) activation perturbed ER membrane integrity. After chronic incubation (4-24 h), C5b-9 increased bip and grp94 mRNAs and proteins, and the increases were dependent on cPLA(2). Expression of bip-antisense mRNA reduced stimulated bip protein expression and enhanced complement-dependent GEC injury. Glomerular bip and grp94 proteins were up-regulated in proteinuric rats with PHN, as compared with normal control. Pretreatment of rats with tunicamycin or adriamycin, which increase ER stress protein expression, reduced proteinuria in PHN. Thus, C5b-9 injures the ER and enhances ER stress protein expression, in part, via activation of cPLA(2). ER stress protein induction is a novel mechanism of protection from complement attack.
Cybulsky
Andrey V
AV
Department of Medicine, McGill University Health Centre, Montreal, Quebec H3A 1A1, Canada. andrey.cybulsky@mcgill.ca
Takano
Tomoko
T
Papillon
Joan
J
Khadir
Abdelkrim
A
Liu
Jianhong
J
Peng
Hongwei
H
D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002352:Carrier Proteins / Q000096:biosynthesis*; D002478:Cells, Cultured; D015938:Complement Membrane Attack Complex / Q000633:toxicity*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D004847:Epithelial Cells / Q000378:metabolism; D005921:Glomerulonephritis / Q000209:etiology; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D007678:Kidney Glomerulus / Q000378:metabolism* / Q000473:pathology; D008565:Membrane Proteins / Q000096:biosynthesis*; D018832:Molecular Chaperones / Q000096:biosynthesis*; D010741:Phospholipases A / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats
D002352:Carrier Proteins; D015938:Complement Membrane Attack Complex; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D012333:RNA, Messenger; C018551:glucose-regulated proteins; D016718:Arachidonic Acid; D010741:Phospholipases A