Endothelin-induced cytoskeletal actin re-organization in cultured astrocytes: inhibition by C3 ADP-ribosyltransferase.
We investigated signal transduction mechanisms of endothelin (ET) receptor-mediated actin re-organization of rat cultured astrocytes. Staining of filamentous actin (F-actin) showed that stress fibers were a prominent cytoskeletal actin structure in protoplasmic astrocytes. A treatment with 0.5 mM dibutyryl cAMP (DBcAMP) caused cytoplasmic retraction and disappearance of stress fibers of astrocytes. A subsequent addition of 1 nM ET-3 after the DBcAMP treatment expanded the cytoplasm and stimulated stress fiber formation. ET-1, sarafotoxin S6b, and [Ala1,3,11,16]-ET-1 had similar effects. Pre-treatment with 0.1 microgram/ml pertussis toxin (PTX) and chelation of cytosolic Ca2+ did not affect astrocytic stress fiber formation by ET-3. ET-3 stimulated stress fiber formation in stellate astrocytes induced by 50 microM ML-9, 20 microM W-7, and 5 microM cytochalasin B (CB). Cytoplasmic microinjection of C3ADP-ribosyltransferase of C. botulinum (C3 enzyme), which impairs the interaction between rho proteins and the effectors, prevented ET-3-induced stress fiber formation and cytoplasmic expansion in DBcAMP-and CB-treated cells. Effects of ET-1 and sarafotoxin on stress fiber formation were also prevented by C3 enzyme. On the other hand, injection of C3 enzyme did not affect increase in cytoplasmic Ca2+ levels induced by ET-3. These results suggest that rho proteins are involved in the ET receptor-mediated actin re-organization of astrocytes.
Koyama
Y
Y
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Osaka University, Suita, Japan.
Baba
A
A
D036002:ADP Ribose Transferases / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D001905:Botulinum Toxins; D002478:Cells, Cultured; D003593:Cytoplasm / Q000187:drug effects / Q000648:ultrastructure; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D016232:Endothelins / Q000494:pharmacology*; D008845:Microinjections; D051381:Rats; D017208:Rats, Wistar; D017466:Receptors, Endothelin / Q000187:drug effects / Q000378:metabolism; D012234:Rho Factor; D015398:Signal Transduction / Q000187:drug effects
D000199:Actins; D003598:Cytoskeletal Proteins; D016232:Endothelins; D017466:Receptors, Endothelin; D012234:Rho Factor; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins