Multifaceted role of Rho, Rac, Cdc42 and Ras in intercellular junctions, lessons from toxins.
Tight junctions (TJs) and adherens junctions (AJs) are dynamic structures linked to the actin cytoskeleton, which control the paracellular permeability of epithelial and endothelial barriers. TJs and AJs are strictly regulated in a spatio-temporal manner by a complex signaling network, including Rho/Ras-GTPases, which have a pivotal role. Rho preferentially regulates TJs by controlling the contraction of apical acto-myosin filaments, whereas Rac/Cdc42 mainly coordinate the assembly-disassembly of AJ components. However, a subtle balance of Rho/Ras-GTPase activity and interplay between these molecules is required to maintain an optimal organization and function of TJs and AJs. Conversely, integrity of intercellular junctions generates signals through Rho-GTPases, which are involved in the regulation of multiple cellular processes. Rho/Ras-GTPases and the control of intercellular junctions are the target of various bacterial toxins responsible for severe diseases in man and animals, and are part of their mechanism of action. This review focuses on the regulation of TJs and AJs by Rho/Ras-GTPases through molecular approaches and bacterial toxins.
Institut Pasteur, Unité des Bactéries anaérobies et Toxines, 75724 Paris cedex151, France. mpopoff@pasteur.fr
Michel R
MR
Popoff
Blandine
B
Geny
D000205:Actomyosin / Q000502:physiology; D022005:Adherens Junctions / Q000187:drug effects / Q000502:physiology*; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology*; D006801:Humans; D015398:Signal Transduction / Q000502:physiology; D019108:Tight Junctions / Q000187:drug effects / Q000502:physiology*; D020764:cdc42 GTP-Binding Protein / Q000502:physiology*; D020744:rac GTP-Binding Proteins / Q000502:physiology*; D018631:ras Proteins / Q000502:physiology*; D020741:rho GTP-Binding Proteins / Q000502:physiology*; D020743:rhoB GTP-Binding Protein / Q000502:physiology*
D001427:Bacterial Toxins; D000205:Actomyosin; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D018631:ras Proteins; D020741:rho GTP-Binding Proteins; D020743:rhoB GTP-Binding Protein