title: Evidence for Rho protein regulation of renal tubular epithelial cell function.
abstract: BACKGROUND
  Rho proteins are small guanine 5'-triphosphate (GTP)-binding proteins felt to be important regulators of several aspects of cell function, including the organization of the actin cytoskeleton. The effects of Rho proteins on the regulation of renal tubular epithelial cell function are not known.
  
  
  METHODS
  Selected bacterial toxins that inhibit Rho protein function were used to examine the effect of Rho in cultured renal tubular epithelial cells.
  
  
  RESULTS
  Clostridium difficile toxin A significantly and dose dependently inhibited LLC-PK(1) cell (3)H-thymidine uptake and healing of small wounds made in confluent monolayers, and it induced apoptosis. A second Clostridium difficile toxin (toxin B) that acted via a different receptor also impaired LLC-PK(1) thymidine uptake and wound healing, and it induced apoptosis. A third bacterial toxin, C3 toxin from Clostridium botulinum, also impaired LLC-PK(1) thymidine uptake and stimulated apoptosis in LLC-PK(1) cells. Since Rho inhibition disrupted organization of the actin cytoskeleton, we examined the effects of another agent that disrupted the actin cytoskeleton (cytochalasin D) and found significant dose-dependent effects that impaired LLC-PK1 thymidine uptake and wound healing and that induced apoptosis. The effects of toxin A and cytochalasin D to induce apoptosis were not associated with significant changes in expression of Bcl-2, BAD, or BAK proteins and were significantly attenuated by a pancaspase inhibitor.
  
  
  CONCLUSIONS
  Our results suggest that Rho proteins are important endogenous regulators of several aspects of renal tubular epithelial cell function, including proliferation, migration, and apoptosis. Further studies are needed to clarify the cellular mechanisms of Rho regulation of renal epithelial cell function.
authors.affiliation: Department of Medicine, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. Robert.Anderson@UCHSC.edu
authors.forename: R J
authors.initials: RJ
authors.lastname: Anderson
authors.forename: C J
authors.initials: CJ
authors.lastname: Ray
authors.forename: M R
authors.initials: MR
authors.lastname: Popoff
mesh_terms: D036002:ADP Ribose Transferases / Q000494:pharmacology; D000546:Amanitins; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001427:Bacterial Toxins / Q000494:pharmacology; D001905:Botulinum Toxins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D015638:Cytochalasin D / Q000494:pharmacology; D004357:Drug Synergism; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology; D005456:Fluorescent Dyes; D007684:Kidney Tubules / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018374:LLC-PK1 Cells / Q000187:drug effects; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D012235:Rhodamines; D013194:Staining and Labeling; D013552:Swine; D013936:Thymidine / Q000493:pharmacokinetics; D020741:rho GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D000546:Amanitins; D000590:Amino Acid Chloromethyl Ketones; D001427:Bacterial Toxins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D005456:Fluorescent Dyes; D019384:Nucleic Acid Synthesis Inhibitors; D012235:Rhodamines; C103192:butyloxycarbonyl-O-methyl-aspartyl-fluoromethyl ketone; D015638:Cytochalasin D; C018358:phallotoxin; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D020741:rho GTP-Binding Proteins; D013936:Thymidine