Amyloid Precursor Protein (APP) Affects Global Protein Synthesis in Dividing Human Cells

J Cell Physiol. 2015 May;230(5):1064-74. doi: 10.1002/jcp.24835.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / metabolism
  • Amyloid Precursor Protein Secretases / antagonists & inhibitors
  • Amyloid Precursor Protein Secretases / metabolism
  • Amyloid beta-Protein Precursor / deficiency
  • Amyloid beta-Protein Precursor / metabolism*
  • Animals
  • Carcinoma, Non-Small-Cell Lung / enzymology
  • Carcinoma, Non-Small-Cell Lung / genetics
  • Carcinoma, Non-Small-Cell Lung / pathology
  • Cell Division*
  • Cell Hypoxia
  • Cell Line, Tumor
  • Down-Regulation
  • Eukaryotic Initiation Factor-4A / metabolism
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Intracellular Signaling Peptides and Proteins / metabolism
  • Lung Neoplasms / enzymology
  • Lung Neoplasms / genetics
  • Lung Neoplasms / pathology
  • Mechanistic Target of Rapamycin Complex 1
  • Mice
  • Models, Biological
  • Multiprotein Complexes / metabolism
  • Nuclear Proteins / metabolism
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Phosphothreonine / metabolism
  • Protein Biosynthesis*
  • RNA Caps / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Substrate Specificity
  • TOR Serine-Threonine Kinases / metabolism

Substances

  • Adaptor Proteins, Signal Transducing
  • Amyloid beta-Protein Precursor
  • EIF4EBP1 protein, human
  • Intracellular Signaling Peptides and Proteins
  • Multiprotein Complexes
  • Nuclear Proteins
  • Phosphoproteins
  • RNA Caps
  • RNA, Messenger
  • STYX protein, human
  • Phosphothreonine
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Extracellular Signal-Regulated MAP Kinases
  • Eukaryotic Initiation Factor-4A
  • Amyloid Precursor Protein Secretases