title: STAT5a activation mediates the epithelial to mesenchymal transition induced by oncogenic RhoA.
abstract: The involvement of Rho GTPases in signal transduction pathways leading to transcription activation is one of the major roles of this family of GTPases. Thus, the identification of transcription factors regulated by Rho GTPases and the understanding of the mechanisms of their activation and its biological outcome are of great interest. Here, we provide evidence that Rho GTPases modulate Stat5a, a transcription factor of the family of signal transducers and activators of transcription. RhoA triggers tyrosine phosphorylation (Y696) of Stat5a via a JAK2-dependent mechanism and promotes DNA-binding activity of Stat5a. Tyrosine phosphorylation of Stat5a is also stimulated physiologically by lysophosphatidic acid (LPA) in a Rho-dependent manner. Simultaneously, RhoA reduces serine phosphorylation of Stat5a at both serine residues S726 and S780, resulting in a further increase of activity as defined by mutagenesis experiments. Furthermore, serine dephosphorylation of Stat5a by RhoA does not take place by down-modulation of either JNK1, MEK1, or p38 MAP kinases, as determined by transfection experiments or chemical inhibition of both MEK1, p38, and JNK serine kinases. Thus, RhoA regulates Stat5a via tyrosine phosphorylation and via a yet to be determined novel down-modulating pathway that involves serine dephosphorylation. Finally, we provide evidence for a role of Stat5a in RhoA-induced epithelial-to-mesenchymal transition with concomitant increase in vimentin expression, E-cadherin down-regulation, and cell motility.
authors.affiliation: Instituto de Investigaciones Biomédicas, CSIC, Madrid, Spain.
authors.forename: Salvador Aznar
authors.initials: SA
authors.lastname: Benitah
authors.forename: Pilar F
authors.initials: PF
authors.lastname: Valerón
authors.forename: Hallgeir
authors.initials: H
authors.lastname: Rui
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Lacal
mesh_terms: D004268:DNA-Binding Proteins / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D053614:Janus Kinase 2; D008648:Mesoderm / Q000378:metabolism*; D008894:Milk Proteins; D010766:Phosphorylation; D011388:Prolactin / Q000235:genetics; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D050799:STAT5 Transcription Factor; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D025521:Tumor Suppressor Proteins; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D008894:Milk Proteins; D011518:Proto-Oncogene Proteins; D050799:STAT5 Transcription Factor; C494092:STAT5A protein, human; D015534:Trans-Activators; D025521:Tumor Suppressor Proteins; D011388:Prolactin; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D020742:rhoA GTP-Binding Protein