title: Atypical protein kinase C phosphorylates Par6 and facilitates transforming growth factor β-induced epithelial-to-mesenchymal transition.
abstract: Epithelial-to-mesenchymal transition (EMT) is controlled by cellular signaling pathways that trigger the loss of cell-cell adhesion and lead to the restructuring of the cell cytoskeleton. Transforming growth factor β (TGF-β) has been shown to regulate cell plasticity through the phosphorylation of Par6 on a conserved serine residue (S345) by the type II TGF-β receptor. We show here that atypical protein kinase C (aPKC) is an essential component to this signaling pathway in non-small-cell lung cancer (NSCLC) cells. We show that the aPKC, PKCι, interacts with TGF-β receptors through Par6 and that these proteins localize to the leading edge of migrating cells. Furthermore, Par6 phosphorylation on serine 345 by TGF-β receptors is enhanced in the presence of aPKC. aPKC kinase activity, as well as an association with Par6, were found to be important for Par6 phosphorylation. In effect, small interfering RNA-targeting aPKC reduces TGF-β-induced RhoA and E-cadherin loss, cell morphology changes, stress fiber production, and the migration of NSCLC cells. Interestingly, reintroduction of a phosphomimetic Par6 (Par6-S345E) into aPKC-silenced cells rescues both RhoA and E-cadherin loss with TGF-β stimulation. In conclusion, our results suggest that aPKCs cooperate with TGF-β receptors to regulate phospho-Par6-dependent EMT and cell migration.
authors.affiliation: Department of Physiology and Pharmacology, Western University, London, Ontario, Canada.
authors.forename: Adrian
authors.initials: A
authors.lastname: Gunaratne
authors.forename: Boun L
authors.initials: BL
authors.lastname: Thai
authors.forename: Gianni M
authors.initials: GM
authors.lastname: Di Guglielmo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D015820:Cadherins / Q000378:metabolism; D002289:Carcinoma, Non-Small-Cell Lung / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D045744:Cell Line, Tumor; D002465:Cell Movement; D058750:Epithelial-Mesenchymal Transition; D006801:Humans; D008168:Lung / Q000166:cytology / Q000378:metabolism; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D025941:Protein Interaction Mapping; D011493:Protein Kinase C / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D051381:Rats; D018125:Receptors, Transforming Growth Factor beta / Q000032:analysis / Q000378:metabolism; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D015820:Cadherins; C499657:PARD6A protein, human; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; C115015:PKC-3 protein; D011493:Protein Kinase C; D020742:rhoA GTP-Binding Protein