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Infection and Immunity, August 2002, p. 4053-4058, Vol. 70, No. 8
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.8.4053-4058.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Proteasomal Degradation of Cytotoxic Necrotizing Factor 1-Activated Rac

Maria Lerm,1 Marius Pop,1 Gerhard Fritz,2 Klaus Aktories,1 and Gudula Schmidt1*

Institut für Experimentelle und Klinische Pharmakologie und Toxikologie, Albert-Ludwigs-Universität Freiburg, D-79104 Freiburg,1 Institut für Toxikologie, D-55131 Mainz, Germany2

Received 4 February 2002/ Returned for modification 21 March 2002/ Accepted 24 April 2002

The cytotoxic necrotizing factor 1 (CNF1) from Escherichia coli has been shown to activate members of the Rho family by deamidation of glutamine 63. This amino acid is essential for hydrolysis of GTP, and any substitution results in a constitutively active Rho. Activation of Rho induces the formation of stress fibers, filopodia, and membrane ruffles due to activation of RhoA, Cdc42, and Rac, respectively. Here we show that the level of endogenous Rac decreased in CNF1-treated HEK293 and HeLa cells. The amount of mRNA remained unaffected, leaving the possibility that Rac is subject to proteolytic degradation. Treatment of cells with lactacystin, an inhibitor of the 26S proteasome, protected Rac from degradation. We have previously shown that CNF1 activates the c-Jun N-terminal kinase (JNK) only transiently in HeLa cells (M. Lerm, J. Selzer, A. Hoffmeyer, U. R. Rapp, K. Aktories, and G. Schmidt, Infect. Immun. 67:496-503, 1998). Here we show that CNF1-induced JNK activation is stabilized in the presence of lactacystin. The data indicate that Rac is degraded by a proteasome-dependent pathway in CNF1-treated cells.


* Corresponding author. Mailing address: Department of Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Albertstr. 25, 79104 Freiburg, Germany. Phone: 0049-761-203-5316. Fax: 0049-761-203-5311. E-mail: gudschmi{at}uni-freiburg.de.

Editor: D. L. Burns


Infection and Immunity, August 2002, p. 4053-4058, Vol. 70, No. 8
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.8.4053-4058.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.




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