title: Pak1 phosphorylation of snail, a master regulator of epithelial-to-mesenchyme transition, modulates snail's subcellular localization and functions.
abstract: The process of epithelial-mesenchymal transition plays a pivotal role in the conversion of early stage tumors into invasive malignancies, and has been shown to be regulated by the zinc finger phosphoprotein, Snail; however, no upstream signaling kinases have been shown to modulate Snail functions. Since the invasiveness of breast cancer cells is also influenced by p21-activated kinase 1 (Pak1) signaling, we investigated Pak1's potential mechanistic role in the regulation of Snail functions. We found for the first time that Pak1 promotes transcription repression activity of Snail from E-cadherin, occludin, and aromatase promoters. Pak1 regulates the repressor activity of Snail by phosphorylating on Ser(246). Pak1 phosphorylation of Snail supports Snail's accumulation in the nucleus as well as its repressor functions. A Ser(246)Ala substitution in Snail or Pak1 knockdown by short interference RNA blocked Pak1-mediated Snail phosphorylation, leading to increased cytoplasmic accumulation of Snail and attenuation of Snail repressor activity in breast cancer cells. The regulation of phosphorylation and function of Snail by Pak1 represents a novel mechanism by which a signaling kinase might contribute to the process of epithelial-mesenchymal transition.
authors.affiliation: Department of Molecular and Cellular Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA.
authors.forename: Zhibo
authors.initials: Z
authors.lastname: Yang
authors.forename: Suresh
authors.initials: S
authors.lastname: Rayala
authors.forename: Diep
authors.initials: D
authors.lastname: Nguyen
authors.forename: Ratna K
authors.initials: RK
authors.lastname: Vadlamudi
authors.forename: Shiuan
authors.initials: S
authors.lastname: Chen
authors.forename: Rakesh
authors.initials: R
authors.lastname: Kumar
mesh_terms: D000595:Amino Acid Sequence; D001943:Breast Neoplasms / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D006801:Humans; D008648:Mesoderm / Q000378:metabolism / Q000473:pathology; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D000071250:Snail Family Transcription Factors; D013347:Subcellular Fractions / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D054462:p21-Activated Kinases
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; C000604451:sna protein, Drosophila; C515903:PAK1 protein, human; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases