A bacterial cytotoxin identifies the RhoA exchange factor Net1 as a key effector in the response to DNA damage

Authors

Lina Guerra, Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
Heather S. Carr, Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas, United States of America
Agneta Richter-Dahlfors, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden
Maria G Masucci, Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
Monica Thelestam, Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
Jeffrey A Frost, Department of Integrative Biology and Pharmacology, University of Texas Health Science Center at Houston, Houston, Texas, United States of AmericaFollow
Teresa Frisan, Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden

Publication Date

5-28-2008

Journal

PLoS ONE

Abstract

BACKGROUND: Exposure of adherent cells to DNA damaging agents, such as the bacterial cytolethal distending toxin (CDT) or ionizing radiations (IR), activates the small GTPase RhoA, which promotes the formation of actin stress fibers and delays cell death. The signalling intermediates that regulate RhoA activation and promote cell survival are unknown. PRINCIPAL FINDINGS: We demonstrate that the nuclear RhoA-specific Guanine nucleotide Exchange Factor (GEF) Net1 becomes dephosphorylated at a critical inhibitory site in cells exposed to CDT or IR. Expression of a dominant negative Net1 or Net1 knock down by iRNA prevented RhoA activation, inhibited the formation of stress fibers, and enhanced cell death, indicating that Net1 activation is required for this RhoA-mediated responses to genotoxic stress. The Net1 and RhoA-dependent signals involved activation of the Mitogen-Activated Protein Kinase p38 and its downstream target MAPK-activated protein kinase 2. SIGNIFICANCE: Our data highlight the importance of Net1 in controlling RhoA and p38 MAPK mediated cell survival in cells exposed to DNA damaging agents and illustrate a molecular pathway whereby chronic exposure to a bacterial toxin may promote genomic instability.

Keywords

Actins, Bacteria, Bacterial Toxins, Base Sequence, Cell Line, DNA Damage, Humans, Oncogene Proteins, RNA, p38 Mitogen-Activated Protein Kinases

Comments

PMCID: PMC2386254

href="http://dx.doi.org/10.1371/journal.pone.0002254 "