convergent use of rhogap toxins by eukaryotic parasites and bacterial pathogens收敛使用rhogap毒素真核寄生虫和细菌病原体.pdf

Convergent Use of RhoGAP Toxins by Eukaryotic Parasites and Bacterial Pathogens 1 1 2 1 ` ´ 1* Dominique Colinet , Antonin Schmitz , Delphine Depoix , Didier Crochard , Marylene Poirie ´ 1 UMR 1112 UNSA-INRA ‘‘Reponses des Organismes aux Stress Environnementaux’’, Sophia-Antipolis, France, 2 USM504 ‘‘Biologie Fonctionnelle des Protozoaires’’ - EA3335 ´ Museum National d’Histoire Naturelle, Paris, France Inactivation of host Rho GTPases is a widespread strategy employed by bacterial pathogens to manipulate mammalian cellular functions and avoid immune defenses. Some bacterial toxins mimic eukaryotic Rho GTPase-activating proteins (GAPs) to inactivate mammalian GTPases, probably as a result of evolutionary convergence. An intriguing question remains whether eukaryotic pathogens or parasites may use endogenous GAPs as immune-suppressive toxins to target the same key genes as bacterial pathogens. Interestingly, a RhoGAP domain–containing protein, LbGAP, was recently characterized from the parasitoid wasp Leptopilina boulardi, and shown to protect parasitoid eggs from the immune response of Drosophila host larvae. We demonstrate here that LbGAP has structural characteristics of eukaryotic RhoGAPs but that it acts similarly to bacterial RhoGAP toxins in mammals. First, we show by immunocytochemistry that LbGAP enters Drosophila immune cells, plasmatocytes and lamellocytes, and that morphological changes in lamellocytes are correlated with the quantity of LbGAP they contain. Demonstration that LbGAP displays a GAP activity and specifically interacts with the active, GTP-bound form of the two Drosophila Rho GTPases Rac1 and Rac2, both required for successful encapsulation of Leptopilina eggs, was then achieved using biochemical tests, yeast two-hybr