title: Amyloid precursor protein (APP) affects global protein synthesis in dividing human cells.
abstract: Hypoxic non-small cell lung cancer (NSCLC) is dependent on Notch-1 signaling for survival. Targeting Notch-1 by means of γ-secretase inhibitors (GSI) proved effective in killing hypoxic NSCLC. Post-mortem analysis of GSI-treated, NSCLC-burdened mice suggested enhanced phosphorylation of 4E-BP1 at threonines 37/46 in hypoxic tumor tissues. In vitro dissection of this phenomenon revealed that Amyloid Precursor Protein (APP) inhibition was responsible for a non-canonical 4E-BP1 phosphorylation pattern rearrangement-a process, in part, mediated by APP regulation of the pseudophosphatase Styx. Upon APP depletion we observed modifications of eIF-4F composition indicating increased recruitment of eIF-4A to the mRNA cap. This phenomenon was supported by the observation that cells with depleted APP were partially resistant to silvestrol, an antibiotic that interferes with eIF-4A assembly into eIF-4F complexes. APP downregulation in dividing human cells increased the rate of global protein synthesis, both cap- and IRES-dependent. Such an increase seemed independent of mTOR inhibition. After administration of Torin-1, APP downregulation and Mechanistic Target of Rapamycin Complex 1 (mTORC-1) inhibition affected 4E-BP1 phosphorylation and global protein synthesis in opposite fashions. Additional investigations indicated that APP operates independently of mTORC-1. Key phenomena described in this study were reversed by overexpression of the APP C-terminal domain. The presented data suggest that APP may be a novel regulator of protein synthesis in dividing human cells, both cancerous and primary. Furthermore, APP appears to affect translation initiation using mechanisms seemingly dissimilar to mTORC-1 regulation of cap-dependent protein synthesis.
authors.affiliation: Department of Pathology, Oncology Institute, Loyola University Chicago Medical Center, Maywood, Illinois.
authors.forename: Anna
authors.initials: A
authors.lastname: Sobol
authors.forename: Paola
authors.initials: P
authors.lastname: Galluzzo
authors.forename: Shuang
authors.initials: S
authors.lastname: Liang
authors.forename: Brittany
authors.initials: B
authors.lastname: Rambo
authors.forename: Sylvia
authors.initials: S
authors.lastname: Skucha
authors.forename: Megan J
authors.initials: MJ
authors.lastname: Weber
authors.forename: Sara
authors.initials: S
authors.lastname: Alani
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bocchetta
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D053829:Amyloid Precursor Protein Secretases / Q000037:antagonists & inhibitors / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000172:deficiency / Q000378:metabolism*; D000818:Animals; D002289:Carcinoma, Non-Small-Cell Lung / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D018797:Cell Cycle Proteins; D002455:Cell Division; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D015536:Down-Regulation; D039601:Eukaryotic Initiation Factor-4A / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D008175:Lung Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism; D014176:Protein Biosynthesis; D012315:RNA Caps / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D016564:Amyloid beta-Protein Precursor; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012315:RNA Caps; D012333:RNA, Messenger; C584541:STYX protein, human; D010769:Phosphothreonine; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D039601:Eukaryotic Initiation Factor-4A; D053829:Amyloid Precursor Protein Secretases