Differential regulation of the two RhoA-specific GEF isoforms Net1/Net1A by TGF-β and miR-24: role in epithelial-to-mesenchymal transition
2012 (English)In: Oncogene, ISSN 0950-9232, Oncogene, ISSN 1476-5594, Vol. 31, no 23, 2862-2875 p.Article in journal (Refereed) Published
In the present study we analyzed the regulation of the two isoforms of the RhoA-specific guanine nucleotide exchange factor Net1 by transforming growth factor-β (TGF-β) in keratinocytes. We report that short-term TGF-β treatment selectively induced Net1 isoform2 (Net1A) but not Net1 isoform1. This led to upregulation of cytoplasmic Net1A protein levels that were necessary for TGF-β-mediated RhoA activation. Smad signaling and the MAPK/ERK kinase (MEK)/extracellular signal-regulated kinase (ERK) pathway were involved in Net1A upregulation by TGF-β. Interestingly, long-term TGF-β treatment resulted in Net1 mRNA downregulation and Net1A protein degradation by the proteasome. Furthermore, we identified the microRNA miR-24 as a novel post-transcriptional regulator of Net1A expression. Silencing of Net1A resulted in disruption of E-cadherin- and zonula occludens-1 (ZO-1)-mediated junctions, as well as expression of the transcriptional repressor of E-cadherin, Slug and the mesenchymal markers N-cadherin, plasminogen activator inhibitor-1 (PAI-1) and fibronectin, indicating that late TGF-β-induced downregulation of Net1A is involved in epithelial-to-mesenchymal transition (EMT). Finally, miR-24 was found to be implicated in the regulation of the EMT program in response to TGF-β and was shown to be directly involved in the TGF-β-induced breast cancer cell invasiveness through Net1A regulation. Our results emphasize the importance of Net1 isoform2 in the short- and long-term TGF-β-mediated regulation of EMT.
Place, publisher, year, edition, pages
2012. Vol. 31, no 23, 2862-2875 p.
TGF-beta, Net1A, RhoA, EMT, miR-24
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:uu:diva-159990DOI: 10.1038/onc.2011.457ISI: 000305277900006PubMedID: 21986943OAI: oai:DiVA.org:uu-159990DiVA: diva2:447728