title: SchA-p85-FAK complex dictates isoform-specific activation of Akt2 and subsequent PCBP1-mediated post-transcriptional regulation of TGFβ-mediated epithelial to mesenchymal transition in human lung cancer cell line A549.
abstract: A post-transcriptional pathway by which TGF-β modulates expression of specific proteins, Disabled-2 (Dab2) and Interleukin-like EMT Inducer (ILEI), inherent to epithelial to mesenchymal transition (EMT) in murine epithelial cells through Akt2-mediated phosphorylation of poly r(C) binding protein (PCBP1), has been previously elucidated. The aims of the current study were to determine if the same mechanism is operative in the non-small cell lung cancer (NSCLC) cell line, A549, and to delineate the underlying mechanism. Steady-state transcript and protein expression levels of Dab2 and ILEI were examined in A549 cells treated with TGF-β for up to 48 h. Induction of translational de-repression in this model was quantified by polysomal fractionation followed by qRT-PCR. The underlying mechanism of isoform-specific activation of Akt2 was elucidated through a combination of co-immunoprecipitation studies. TGF-β induced EMT in A549 cells concomitant with translational upregulation of Dab2 and ILEI proteins through isoform-specific activation of Akt2 followed by phosphorylation of PCBP1 at serine-43. Our experiments further elucidated that the adaptor protein SchA is phosphorylated at tyrosine residues following TGF-β treatment, which initiated a signaling cascade resulting in the sequential recruitment of p85 subunit of PI3K and focal adhesion kinase (FAK). The SchA-FAK-p85 complex subsequently selectively recruited and activated Akt2, not Akt1. Inhibition of the p85 subunit through phosphorylated 1257 peptide completely attenuated EMT in these cells. We have defined the underlying mechanism responsible for isoform-specific recruitment and activation of Akt2, not Akt1, during TGF-β-mediated EMT in A549 cells. Inhibition of the formation of this complex thus represents an important and novel therapeutic target in metastatic lung carcinoma.
authors.affiliation: The Department of Special Medical Treatment-Respiratory Disease, Beijing Shijitan Hospital, Capital Medical University, Beijing, China.
authors.forename: Xinying
authors.initials: X
authors.lastname: Xue
authors.forename: Xin
authors.initials: X
authors.lastname: Wang
authors.forename: Yuxia
authors.initials: Y
authors.lastname: Liu
authors.forename: Guigen
authors.initials: G
authors.lastname: Teng
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.forename: Xuefeng
authors.initials: X
authors.lastname: Zang
authors.forename: Kaifei
authors.initials: K
authors.lastname: Wang
authors.forename: Jinghui
authors.initials: J
authors.lastname: Zhang
authors.forename: Yali
authors.initials: Y
authors.lastname: Xu
authors.forename: Jianxin
authors.initials: J
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Pan
mesh_terms: D045744:Cell Line, Tumor; D058543:Class Ia Phosphatidylinositol 3-Kinase / Q000502:physiology*; D004268:DNA-Binding Proteins; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects*; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000502:physiology*; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000502:physiology*; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D010766:Phosphorylation; D020033:Protein Isoforms / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D016601:RNA-Binding Proteins; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D004268:DNA-Binding Proteins; D034441:Heterogeneous-Nuclear Ribonucleoproteins; C094604:PCBP1 protein, human; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D016212:Transforming Growth Factor beta; D058543:Class Ia Phosphatidylinositol 3-Kinase; D051416:Focal Adhesion Protein-Tyrosine Kinases; C494921:AKT2 protein, human; D051057:Proto-Oncogene Proteins c-akt