title: PTEN regulates colorectal epithelial apoptosis through Cdc42 signalling.
abstract: BACKGROUND
  Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) regulation of the Rho-like GTPase Cdc42 has a central role in epithelial polarised growth, but effects of this molecular network on apoptosis remain unclear.
  
  
  METHODS
  To investigate the role of Cdc42 in PTEN-dependent cell death, we used flow cytometry, in vitro pull-down assays, poly(ADP ribose) polymerase (PARP) cleavage and other immunoblots in isogenic PTEN-expressing and -deficient colorectal cells (HCT116PTEN(+/+), HCT116PTEN(-/-), Caco2 and Caco2 ShPTEN cells) after transfection or treatment strategies.
  
  
  RESULTS
  The PTEN knockout or suppression by short hairpin RNA or small interfering RNA (siRNA) inhibited Cdc42 activity, PARP cleavage and/or apoptosis in flow cytometry assays. Transfection of cells with wild-type or constitutively active Cdc42 enhanced PARP cleavage, whereas siRNA silencing of Cdc42 inhibited PARP cleavage and/or apoptosis. Pharmacological upregulation of PTEN by sodium butyrate (NaBt) treatment enhanced Cdc42 activity, PARP cleavage and apoptosis, whereas Cdc42 siRNA suppressed NaBt-induced PARP cleavage. Cdc42-dependent signals can suppress glycogen synthase kinase-β (GSK3β) activity. Pharmacological inhibition of GSK3β by lithium chloride treatment mimicked effects of Cdc42 in promotion of PARP cleavage and/or apoptosis.
  
  
  CONCLUSIONS
  Phosphatase and tensin homologue deleted on chromosome 10 may influence apoptosis in colorectal epithelium through Cdc42 signalling, thus providing a regulatory framework for both polarised growth and programmed cell death.
authors.affiliation: Centre for Cancer Research and Cell Biology, Queen's University of Belfast, Lisburn Road, Belfast BT97BL, UK.
authors.forename: R
authors.initials: R
authors.lastname: Deevi
authors.forename: A
authors.initials: A
authors.lastname: Fatehullah
authors.forename: I
authors.initials: I
authors.lastname: Jagan
authors.forename: M
authors.initials: M
authors.lastname: Nagaraju
authors.forename: V
authors.initials: V
authors.lastname: Bingham
authors.forename: F C
authors.initials: FC
authors.lastname: Campbell
mesh_terms: D017209:Apoptosis; D018938:Caco-2 Cells; D018797:Cell Cycle Proteins / Q000378:metabolism*; D055786:Gene Knockout Techniques; D045325:HCT116 Cells; D006801:Humans; D051059:PTEN Phosphohydrolase / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D000072260:RNA Splicing Factors; D034741:RNA, Small Interfering / Q000494:pharmacology; D016601:RNA-Binding Proteins / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: C112200:CDC40 protein, human; D018797:Cell Cycle Proteins; D000072260:RNA Splicing Factors; D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; D011065:Poly(ADP-ribose) Polymerases; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human