Microtubule dynamics differentially regulates Rho and Rac activity and triggers Rho-independent stress fiber formation in macrophage polykaryons.
Multinucleated giant cells (MNGC) derived from avian peripheral blood monocytes present a dense microtubular network emanating from peripherally located centrosomes. We were interested to study how microtubule and F-actin cytoskeletons cooperate in MNGC to maintain cell shape. Microtubule depolymerization by nocodazole triggered the reorganization of the F-actin cytoskeleton in MNGC that is normally organized into podosomes, cortical actin filaments and membrane ruffles. After nocodazole treatment, F-actin was redistributed into unusual transverse fibers associated with focal adhesion plaques. When microtubules were allowed to repolymerize after nocodazole removal, F-actin appeared transiently, together with the small GTPase Rac, in large membrane ruffles. Using affinity precipitation assays, we show that microtubule depolymerization leads to activation of Rho and inhibition of Rac, whereas microtubule repolymerization induces Rac activation and Rho inhibition. Thus, the level of microtubule polymerization inversely regulates Rho and Rac activity in MNGC. Moreover, using C3 exoenzyme, a known inhibitor of Rho, we demonstrate that both the F-actin fiber formation in response to microtubule depolymerization and the formation of membrane ruffles after microtubule repolymerization occur in C3-treated MNGC, indicating that Rho is not required for these events.
Laboratoire de Biologie Moléculaire et Cellulaire, Ecole Normale Supérieure de Lyon UMR5665, CNRS, ENS Equipe INRA, France.
Stephane
S
Ory
Olivier
O
Destaing
Pierre
P
Jurdic
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000199:Actins / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D002645:Chickens; D015638:Cytochalasin D / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D015726:Giant Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008264:Macrophages / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018613:Microscopy, Confocal; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D015739:Nocodazole / Q000494:pharmacology; D011108:Polymers / Q000378:metabolism; D012266:Ribose / Q000378:metabolism; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D020744:rac GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000187:drug effects / Q000378:metabolism*
D000199:Actins; D003598:Cytoskeletal Proteins; D011108:Polymers; D015638:Cytochalasin D; D012266:Ribose; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; D015739:Nocodazole