title: aPKC alters the TGFβ response in NSCLC cells through both  Smad-dependent and Smad-independent pathways.
abstract: Transforming growth factor b (TGFb) signaling controls many cellular responses including proliferation, epithelial to mesenchymal transition and apoptosis, through the activation of canonical (Smad) as well as non-canonical (e.g., Par6) pathways. Previous studies from our lab have demonstrated that aPKC inhibition regulates TGFb receptor trafficking and signaling. Here, we report that downstream TGFb-dependent transcriptional responses in aPKC-silenced NSCLC cells were reduced compared with those of control cells, despite a temporal extension of Smad2 phosphorylation. We assessed SARA–Smad2–Smad4 association and observed that knockdown of aPKC increased SARA (also known as ZFYVE9) levels and SARA–Smad2 complex formation, increased cytoplasmic retention of Smad2 and reduced Smad2–Smad4 complex formation, which correlated with reduced Smad2 nuclear translocation. Interestingly, we also detected an increase in p38 MAPK phosphorylation and apoptosis in aPKC-silenced cells, which were found to be TRAF6-dependent. Taken together, our results suggest that aPKC isoforms regulate Smad and non-Smad TGFb pathways and that aPKC inhibition sensitizes NSCLC cells to undergo TGFb dependent apoptosis.
authors.forename: Adrian
authors.initials: A
authors.lastname: Gunaratne
authors.forename: Eddie
authors.initials: E
authors.lastname: Chan
authors.forename: Tarek H
authors.initials: TH
authors.lastname: El-Chabib
authors.forename: David
authors.initials: D
authors.lastname: Carter
authors.forename: Gianni M
authors.initials: GM
authors.lastname: Di Guglielmo
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D017209:Apoptosis / Q000235:genetics*; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology*; D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000235:genetics*; D008175:Lung Neoplasms / Q000473:pathology*; D020935:MAP Kinase Signaling System / Q000235:genetics; D046912:Multiprotein Complexes; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D012697:Serine Endopeptidases / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D051901:Smad4 Protein / Q000378:metabolism; D048029:TNF Receptor-Associated Factor 6 / Q000235:genetics / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D046912:Multiprotein Complexes; D011493:Protein Kinase C; D034741:RNA, Small Interfering; D018125:Receptors, Transforming Growth Factor beta; D012697:Serine Endopeptidases; D051899:Smad2 Protein; D051901:Smad4 Protein; D048029:TNF Receptor-Associated Factor 6; D016212:Transforming Growth Factor beta; D048051:p38 Mitogen-Activated Protein Kinases; D000099293:Protein Kinase C-lambda; D000099221:Protein Kinase C zeta; C499657:PARD6A protein, human; C497782:SMAD2 protein, human; C497796:SMAD4 protein, human; C116420:ZFYVE16 protein, human