Role of Rho protein in lovastatin-induced breakdown of actin cytoskeleton.
The Rho GTPases are involved in actin cytoskeleton organization and signal transduction. They need polyisoprenylation for membrane association and activation. Lovastatin, a hydroxymethylglutaryl coenzyme A inhibitor, prevents isoprene synthesis and thereby lipid modification of the Rho protein carboxy terminus. Because lovastatin causes rounding up of cultured cells, we investigated whether the compound acts on the actin cytoskeleton through Rho proteins. Lovastatin treatment decreased F-actin content in a time- and concentration-dependent manner. G-actin content remained unchanged. In lovastatin-treated NIH 3T3 cells, the amount of Rho protein which was ADP-ribosylated by Clostridium botulinum exoenzyme C3 decreased in membranes and increased in the cytosol fraction. Cycloheximide prevented lovastatin-induced rounding up of cells. However, after microinjection or direct application of exoenzyme C3, cells treated with cycloheximide and lovastatin rounded up again. On the contrary, lovastatin-treated, round Swiss 3T3 cells reverted to a flat morphology when microinjected with dominant active RhoA (Val14RhoA). Escherichia coli cytotoxic necrotizing factor (CNF1) which activates Rho proteins caused flattening of round, lovastatin-treated NIH 3T3 cells. These results suggest that lovastatin affects the actin cytoskeleton through inactivation of Rho proteins.
Koch
G
G
Institut für Pharmakologie und Toxikologie, Universität Freiburg, D-79104 Freiburg, Germany.
Benz
C
C
Schmidt
G
G
Olenik
C
C
Aktories
K
K
D016475:3T3 Cells; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003599:Cytoskeleton / Q000378:metabolism*; D003603:Cytotoxins / Q000494:pharmacology; D029968:Escherichia coli Proteins; D019204:GTP-Binding Proteins / Q000502:physiology*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology*; D008148:Lovastatin / Q000494:pharmacology*; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D011817:Rabbits; D020743:rhoB GTP-Binding Protein
D000199:Actins; D001427:Bacterial Toxins; D003603:Cytotoxins; D029968:Escherichia coli Proteins; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008565:Membrane Proteins; C060296:cytotoxic necrotizing factor type 1; D003513:Cycloheximide; D008148:Lovastatin; D019204:GTP-Binding Proteins; D020743:rhoB GTP-Binding Protein