title: Rho isoforms have distinct and specific functions in the process of epithelial to mesenchymal transition in renal proximal tubular cells.
abstract: Epithelial to mesenchymal transition (EMT) is involved in embryological development, cancerous metastatic spread and organ fibrosis, including the kidney. This process is largely driven by transforming growth factor-beta and recent evidence has implicated Rho as a key intracellular signalling molecule. In this study we have used RNA interference to silence the genetically distinct Rho (A, B and C) isoforms to define their individual functions in human kidney epithelial cells undergoing EMT. We demonstrate that the downregulation of the epithelial cell marker E-cadherin is dependent upon the Rho effector, Rho-kinase. However, silencing RhoA or RhoC expression also results in E-cadherin loss, though each by different mechanisms. Loss of RhoA leads to an upregulation of Snail1 and a reduction in the transcription of E-cadherin whereas loss of RhoC upregulates its breakdown via proteasomal degradation. During EMT, the upregulation of alpha-smooth muscle actin can be blocked by inhibiting the expression of RhoA, but not by that of RhoB or RhoC. This effect is independent of Rho-kinase activity. RhoC is the isoform solely responsible for stress fibre formation and inhibiting its expression reduces EMT-induced migration by 50%. RhoB appears to play a role in cell survival as inhibiting its expression leads to >300% increase in cell apoptosis and a relocalization of focal adhesion kinase. We conclude that Rho is a key signalling molecule in the process of EMT but that each isoform has a distinct and specific role.
authors.affiliation: King's College London, Department of Renal Medicine, London, UK.
authors.forename: Nicol
authors.initials: N
authors.lastname: Hutchison
authors.forename: Bruce M
authors.initials: BM
authors.lastname: Hendry
authors.forename: Claire C
authors.initials: CC
authors.lastname: Sharpe
mesh_terms: D015820:Cadherins / Q000378:metabolism; D002465:Cell Movement; D004847:Epithelial Cells / Q000166:cytology*; D055785:Gene Knockdown Techniques; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D008648:Mesoderm / Q000166:cytology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D015820:Cadherins; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D053773:Transforming Growth Factor beta1; D020741:rho GTP-Binding Proteins