Open AccessProteasomal Degradation of Cytotoxic Necrotizing Factor 1-Activated Rac
Author(s) -
Maria Lerm,
Marius Pop,
Gerhard Fritz,
Klaus Aktories,
Gudula Schmidt
Publication year - 2002
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.70.8.4053-4058.2002
Subject(s) - lactacystin , rhoa , proteasome , cdc42 , biology , cytotoxic t cell , hela , microbiology and biotechnology , ubiquitin , hek 293 cells , proteolysis , kinase , biochemistry , proteasome inhibitor , signal transduction , cell , in vitro , enzyme , gene
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.