The actin cytoskeleton facilitates complement-mediated activation of cytosolic phospholipase A2.
Cytosolic PLA(2)-alpha (cPLA(2)) and metabolites of arachidonic acid (AA) are key mediators of complement-dependent glomerular epithelial cell (GEC) injury. Assembly of C5b-9 increases cytosolic Ca(2+) concentration and results in transactivation of receptor tyrosine kinases and activation of PLC-gamma 1 and the 1,2-diacylglycerol (DAG)-PKC pathway. Ca(2+) and PKC are essential for membrane association and increased catalytic activity of cPLA(2). This study addresses the role of the actin cytoskeleton in cPLA(2) activation. Depolymerization of F-actin by cytochalasin D or latrunculin B reduced complement-dependent [(3)H]AA release, as well as the complement-induced increase in cPLA(2) activity. These effects were due to inhibition of [(3)H]DAG production and PKC activation, implying interference with PLC. Complement-dependent [(3)H]AA release was also reduced by jasplakinolide, a compound that stabilizes F-actin and organizes actin filaments at the cell periphery, and calyculin A, which induces condensation of actin filaments at the plasma membrane. The latter drugs did not affect [(3)H]DAG production, suggesting their inhibitory actions were downstream of PKC. Neither cytochalasin D, latrunculin B, nor calyculin A affected association of cPLA(2) with microsomal membranes, and cytochalasin D and latrunculin B did not alter the localization of the endoplasmic reticulum. Stable transfection of constitutively active RhoA induced formation of stress fibers, stabilized F-actin, and attenuated the complement-induced increase in [(3)H]AA. Thus in GEC, cPLA(2) activation is dependent, in part, on actin remodeling. By regulating complement-mediated activation of cPLA(2), the actin cytoskeleton may contribute to the pathophysiology of GEC injury.
Cybulsky
Andrey V
AV
Department of Medicine, McGill University Health Centre, Montreal, Quebec, Canada H3A 1A1. andrey.cybulsky@mcgill.ca
Takano
Tomoko
T
Papillon
Joan
J
Khadir
Abdelkrim
A
Bijian
Krikor
K
Le Berre
Ludmilla
L
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002462:Cell Membrane / Q000201:enzymology; D002478:Cells, Cultured; D003165:Complement System Proteins / Q000494:pharmacology*; D015638:Cytochalasin D / Q000494:pharmacology; D004789:Enzyme Activation; D004847:Epithelial Cells / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure; D066246:ErbB Receptors / Q000378:metabolism; D054513:Group IV Phospholipases A2; D007678:Kidney Glomerulus / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism*; D054467:Phospholipases A2; D051381:Rats; D015398:Signal Transduction; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D019086:Bridged Bicyclo Compounds, Heterocyclic; D013844:Thiazoles; D053778:Thiazolidines; D015638:Cytochalasin D; D016718:Arachidonic Acid; D003165:Complement System Proteins; D066246:ErbB Receptors; D010741:Phospholipases A; D054513:Group IV Phospholipases A2; D054467:Phospholipases A2; D020742:rhoA GTP-Binding Protein; C037068:latrunculin B