Open AccessExoenzyme T of Pseudomonas aeruginosa elicits cytotoxicity without interfering with Ras signal transduction
Author(s) -
Sundin Charlotta,
Henriksson Maria L.,
Hallberg Bengt,
Forsberg Åke,
FrithzLindsten Elisabet
Publication year - 2001
Publication title -
cellular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.542
H-Index - 138
eISSN - 1462-5822
pISSN - 1462-5814
DOI - 10.1046/j.1462-5822.2001.00108.x
Subject(s) - biology , rhoa , gtpase activating protein , microbiology and biotechnology , gtpase , yersinia pseudotuberculosis , signal transduction , rac1 , type three secretion system , secretion , cdc42 , rac gtp binding proteins , virulence , biochemistry , g protein , gene
One virulence strategy used by the opportunistic pathogen Pseudomonas aeruginosa is to target toxic proteins into eukaryotic cells by a type III secretion mechanism. Two of these proteins, ExoS and ExoT, show 75% homology on amino acid level. However, compared with ExoS, ExoT exhibits highly reduced ADP‐ribosylating activity and the role of ExoT in pathogenesis is poorly understood. To study the biological effect of ExoT, we used a strategy by which ExoT was delivered into host cells by the heterologous type III secretion system of Yersinia pseudotuberculosis . ExoT was found to induce a rounded cell morphology and to mediate disruption of actin microfilaments, similar to that induced by an ADP‐ribosylation defective ExoS (E381A) and the related cytotoxin YopE of Y. pseudotuberculosis . In contrast to ExoS, ExoT had no major effect on cell viability and did not modify or inactivate Ras by ADP‐ribosylation in vivo . However, similar to ExoS and YopE, ExoT exhibited GAP (GTPase activating protein) activity on RhoA GTPase in vitro . Interestingly, ExoT(R149K), deficient for GAP activity, still caused a morphological change of HeLa cells. Based on our findings, we suggest that the ADP‐ribosylating activity of ExoT target another, as yet unidentified, host protein that is distinct from Ras.