Rac1 inactivation by lethal toxin from Clostridium sordellii modifies focal adhesions upstream of actin depolymerization.
Inactivation of different small GTPases upon their glucosylation by lethal toxin from Clostridium sordellii strain IP82 (LT-82) is already known to lead to cell rounding, adherens junction (AJ) disorganization and actin depolymerization. In the present work, we observed that LT-82 induces a rapid dephosphorylation of paxillin, a protein regulating focal adhesion (FA), independently of inactivation of paxillin kinases such as Src, Fak and Pyk2. Among the small GTPases inactivated by this toxin, including Rac, Ras, Rap and Ral, we identified Rac1, as responsible for paxillin dephosphorylation using cells overexpressing Rac1(V12). Rac1 inactivation by LT-82 modifies interactions between proteins from AJ and FA complexes as shown by pull-down assays. We showed that in Triton X-100-insoluble membrane proteins from these complexes, namely E-cadherin, beta-catenin, p120-catenin and talin, are decreased upon LT-82 intoxication, a treatment that also induces a rapid decrease in cell phosphoinositide content. Therefore, we proposed that Rac inactivation by LT-82 alters phosphoinositide metabolism leading to FA and AJ complex disorganization and actin depolymerization.
Unité des Bactéries Anaérobies et Toxines, Department of Microbiology, Institut Pasteur, 25 rue du Docteur Roux, Paris Cedex 15, France. blandine.geny@pasteur.fr
Blandine
B
Geny
Alexandre
A
Grassart
Maria
M
Manich
Gaëtan
G
Chicanne
Bernard
B
Payrastre
Nathalie
N
Sauvonnet
Michel R
MR
Popoff
D000199:Actins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000494:pharmacology*; D047989:Paraclostridium sordellii / Q000187:drug effects* / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D022001:Focal Adhesions / Q000187:drug effects* / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D008858:Microscopy, Phase-Contrast; D011485:Protein Binding / Q000187:drug effects; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
D000199:Actins; D001427:Bacterial Toxins; C072292:lethal toxin LT, Clostridium sordellii; D020830:rac1 GTP-Binding Protein