UniProtKB/Swiss-Prot entry P12023

• FUNCTION: Functions as a cell surface receptor and performs physiological functions on the surface of neurons relevant to neurite growth, neuronal adhesion and axonogenesis. Involved in cell mobility and transcription regulation through protein-protein interactions. Can promote transcription activation through binding to APBB1/Tip60 and inhibit Notch signaling through interaction with Numb. Couples to apoptosis-inducing pathways such as those mediated by G(O) and JIP. Inhibits G(o) alpha ATPase activity (By similarity). Acts as a kinesin I membrane receptor, mediating the axonal transport of beta-secretase and presenilin 1. May be involved in copper homeostasis/oxidative stress through copper ion reduction. Can regulate neurite outgrowth through binding to components of the extracellular matrix such as heparin and collagen I and IV (By similarity). The splice isoforms that contain the BPTI domain possess protease inhibitor activity (By similarity).
• FUNCTION: Beta-amyloid peptides are lipophilic metal chelators with metal-reducing activity. Bind transient metals such as copper, zinc and iron. Rat and mouse beta-amyloid peptides bind only weakly transient metals and have little reducing activity due to substitutions of transient metal chelating residues. Beta-APP42 may activate mononuclear phagocytes in the brain and elicit inflammatory responses. Promotes both tau aggregation and TPK II-mediated phosphorylation (By similarity).
• FUNCTION: The gamma-CTF peptides as well as the caspase-cleaved peptides, including C31, are potent enhancers of neuronal apoptosis.
• SUBUNIT: Binds, via its C-terminus, to the PID domain of several cytoplasmic proteins, including APBB family members, the APBA family, MAPK8IP1, SHC1, Numb and Dab1. Binding to Dab1 inhibits its serine phosphorylation. Also interacts with GPCR-like protein BPP, FPRL1, APPBP1, IB1, KNS2 (via its TPR domains), APPBP2 (via BaSS) and DDB1 (By similarity). In vitro, it binds MAPT via the MT-binding domains (By similarity). Associates with microtubules in the presence of ATP and in a kinesin-dependent manner (By similarity). Interacts, through a C-terminal domain, with GNAO1 (By similarity). Amyloid beta-42 binds CHRNA7 in hippocampal neurons (By similarity). Beta-amyloid associates with HADH2 (By similarity). Interacts with ANKS1B (By similarity). Interacts with CPEB1.
• INTERACTION:
  P98084:Apba2; NbExp=1; IntAct=EBI-78814, EBI-81669;
  Q9QXJ1:Apbb1; NbExp=1; IntAct=EBI-78814, EBI-81338;
  P97318:Dab1; NbExp=1; IntAct=EBI-78814, EBI-81680;
  Q9UQF2:MAPK8IP1 (xeno); NbExp=1; IntAct=EBI-78814, EBI-78404;
  Q9UQF2:MAPK8IP1 (xeno); NbExp=1; IntAct=EBI-286828, EBI-78404;
  Q9WVI9:Mapk8ip1; NbExp=2; IntAct=EBI-78814, EBI-74515;
  Q9WVI9-1:Mapk8ip1; NbExp=2; IntAct=EBI-78814, EBI-288461;
  Q9WVI9-1:Mapk8ip1; NbExp=1; IntAct=EBI-286828, EBI-288461;
  Q61120:Shc3; NbExp=1; IntAct=EBI-78814, EBI-79107;
  
• SUBCELLULAR LOCATION: Membrane; Single-pass type I membrane protein. Membrane, clathrin-coated pit. Note=Cell surface protein that rapidly becomes internalized via clathrin-coated pits. During maturation, the immature APP (N-glycosylated in the endoplasmic reticulum) moves to the Golgi complex where complete maturation occurs (O-glycosylated and sulfated). After alpha-secretase cleavage, soluble APP is released into the extracellular space and the C-terminal is internalized to endosomes and lysosomes. Some APP accumulates in secretory transport vesicles leaving the late Golgi compartment and returns to the cell surface. Gamma-CTF(59) peptide is located to both the cytoplasm and nuclei of neurons. It can be translocated to the nucleus through association with Fe65. Beta-APP42 associates with FPRL1 at the cell surface and the complex is then rapidly internalized (By similarity). APP sorts to the basolateral surface in epithelial cells (By similarity). During neuronal differentiation, the Thr-743 phosphorylated form is located mainly in growth cones, moderately in neurites and sparingly in the cell body. Casein kinase phosphorylation can occur either at the cell surface or within a post-Golgi compartment (By similarity).
• ALTERNATIVE PRODUCTS: 4 named isoforms [FASTA] produced by alternative splicing. Additional isoforms seem to exist.

  Name APP770 Isoform ID P12023-1 This is the isoform sequence displayed in this entry.

  Name APP695 Isoform ID P12023-2 Features which should be applied to build the isoform sequence: VSP_000012, VSP_000013.

  Name APP751 Isoform ID P12023-3 Features which should be applied to build the isoform sequence: VSP_000014.

  Name APP714 Isoform ID P12023-4 The sequence of this isoform is not described.

• TISSUE SPECIFICITY: Isoform APP770 is expressed in kidney. Isoform APP751 is widely expressed. Isoform APP695 is expressed in brain, kidney and liver. Isoform APP695, isoform APP714 and isoform APP751 are expressed in several different brain regions including hippocampus, substania nigra pars compacta and cerebellum. In the cerebellum, these isoforms are abundantly expressed in Purkinje cells.
• DOMAIN: The basolateral sorting signal (BaSS) is required for sorting of membrane proteins to the basolateral surface of epithelial cells.
• DOMAIN: The NPXY sequence motif found in many tyrosine-phosphorylated proteins is required for the specific binding of the PID domain. However, additional amino acids either N- or C-terminal to the NPXY motif are often required for complete interaction. The PID domain-containing proteins which bind APP require the YENPTY motif for full interaction. These interactions are independent of phosphorylation on the terminal tyrosine residue. The NPXY site is also involved in clathrin-mediated endocytosis (By similarity).
• PTM: Proteolytically processed under normal cellular conditions. Cleavage by alpha-secretase or alternatively by beta-secretase leads to generation and extracellular release of soluble APP peptides, S-APP-alpha and S-APP-beta, respectively, and the retention of corresponding membrane-anchored C-terminal fragments, C83 and C99. Subsequent processing of C83 by gamma-secretase yields P3 peptides. This is the major secretory pathway and is non-amyloidogenic. Alternatively, presenilin/nicastrin-mediated gamma-secretase processing of C99 releases the amyloid beta proteins, amyloid-beta 40 (Abeta40) and amyloid-beta 42 (Abeta42), major components of amyloid plaques, and the cytotoxic C-terminal fragments, gamma-CTF(50), gamma-CTF(57) and gamma-CTF(59).
• PTM: Proteolytically cleaved by caspases during neuronal apoptosis. Cleavage at Asp-739 by either caspase-3, -8 or -9 results in the production of the neurotoxic C31 peptide and the increased production of beta-amyloid peptides (By similarity).
• PTM: N- and O-glycosylated (By similarity).
• PTM: Phosphorylation in the C-terminal on tyrosine, threonine and serine residues is neuron-specific. Phosphorylation can affect APP processing, neuronal differentiation and interaction with other proteins. The Thr-743 phosphorylated form causes a conformational change which reduces binding of Fe65 family members (By similarity). Phosphorylation on Tyr-757 is required for SHC binding (By similarity).
• PTM: Extracellular binding and reduction of copper, results in a corresponding oxidation of Cys-144 and Cys-158, and the formation of a disulfide bond (By similarity).
• MISCELLANEOUS: Chelation of metal ions, notably copper, iron and zinc, can induce histidine-bridging between beta-amyloid molecules resulting in beta-amyloid-metal aggregates. Rat and mouse beta-amyloid peptides have an arginine residue substituted for the bridging histidine residue and are thus less capable of forming amyloid aggegates. Extracellular zinc-binding increases binding of heparin to APP and inhibits collagen-binding (By similarity).
• SIMILARITY: Belongs to the APP family.
• SIMILARITY: Contains 1 BPTI/Kunitz inhibitor domain.