AMYLOID BETA PEPTIDE (25-35), NMR, 20 STRUCTURES
[A4_HUMAN] Defects in APP are the cause of Alzheimer disease type 1 (AD1) [MIM:104300]. AD1 is a familial early-onset form of Alzheimer disease. It can be associated with cerebral amyloid angiopathy. Alzheimer disease is a neurodegenerative disorder characterized by progressive dementia, loss of cognitive abilities, and deposition of fibrillar amyloid proteins as intraneuronal neurofibrillary tangles, extracellular amyloid plaques and vascular amyloid deposits. The major constituent of these plaques is the neurotoxic amyloid-beta-APP 40-42 peptide (s), derived proteolytically from the transmembrane precursor protein APP by sequential secretase processing. The cytotoxic C-terminal fragments (CTFs) and the caspase-cleaved products such as C31 derived from APP, are also implicated in neuronal death.                          Defects in APP are the cause of cerebral amyloid angiopathy APP-related (CAA-APP) [MIM:605714]. A hereditary localized amyloidosis due to amyloid-beta A4 peptide(s) deposition in the cerebral vessels. The principal clinical characteristics are recurrent cerebral and cerebellar hemorrhages, recurrent strokes, cerebral ischemia, cerebral infarction, and progressive mental deterioration. Patients develop cerebral hemorrhage because of the severe cerebral amyloid angiopathy. Parenchymal amyloid deposits are rare and largely in the form of pre-amyloid lesions or diffuse plaque-like structures. They are Congo red negative and lack the dense amyloid cores commonly present in Alzheimer disease. Some affected individuals manifest progressive aphasic dementia, leukoencephalopathy, and occipital calcifications.    
[A4_HUMAN] 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-KAT5 and inhibits 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. Involved in copper homeostasis/oxidative stress through copper ion reduction. In vitro, copper-metallated APP induces neuronal death directly or is potentiated through Cu(2+)-mediated low-density lipoprotein oxidation. Can regulate neurite outgrowth through binding to components of the extracellular matrix such as heparin and collagen I and IV. The splice isoforms that contain the BPTI domain possess protease inhibitor activity. Induces a AGER-dependent pathway that involves activation of p38 MAPK, resulting in internalization of amyloid-beta peptide and leading to mitochondrial dysfunction in cultured cortical neurons. Provides Cu(2+) ions for GPC1 which are required for release of nitric oxide (NO) and subsequent degradation of the heparan sulfate chains on GPC1.     Beta-amyloid peptides are lipophilic metal chelators with metal-reducing activity. Bind transient metals such as copper, zinc and iron. In vitro, can reduce Cu(2+) and Fe(3+) to Cu(+) and Fe(2+), respectively. Beta-amyloid 42 is a more effective reductant than beta-amyloid 40. Beta-amyloid peptides bind to lipoproteins and apolipoproteins E and J in the CSF and to HDL particles in plasma, inhibiting metal-catalyzed oxidation of lipoproteins. Beta-APP42 may activate mononuclear phagocytes in the brain and elicit inflammatory responses. Promotes both tau aggregation and TPK II-mediated phosphorylation. Interaction with Also bind GPC1 in lipid rafts.     Appicans elicit adhesion of neural cells to the extracellular matrix and may regulate neurite outgrowth in the brain (By similarity).     The gamma-CTF peptides as well as the caspase-cleaved peptides, including C31, are potent enhancers of neuronal apoptosis.     N-APP binds TNFRSF21 triggering caspase activation and degeneration of both neuronal cell bodies (via caspase-3) and axons (via caspase-6).    
Publication Abstract from PubMed
The three-dimensional structure of amyloid beta peptide (25-35), which has neurotoxic activity, in lithium dodecyl sulfate micelles was determined by two-dimensional 1H NMR spectroscopy with simulated annealing calculations. A total of 20 converged amyloid beta peptide structures were obtained on the basis of 110 experimental constraints, including 106 distance constraints reduced from the nuclear Overhauser effect (NOE) connectivities and four torsion angle (phi) constraints. The atomic root mean square difference about averaged coordinates is 1.04 +/- 0.25 A for the backbone atoms (N, C alpha, C) and 1.39 +/- 0.27 A for all heavy atoms of the entire peptide. The molecular structure of amyloid beta peptide in membrane-mimicking environment is composed of a short alpha helix in the C terminal position. The three residues from the N-terminus are disordered, but the remaining eight C-terminal residues are well-ordered, which is supported by the RMSD values of the C-terminal region, Lys28-Leu34. In this region, the RMS differences from averaged coordinates are 0.26 +/- 0.11 A for the backbone atoms (N, C alpha, C) and 0.77 +/- 0.21 A for all heavy atoms, which is very low compared with those for the entire peptide. The four amino acid residues from the N-terminus are hydrophilic and the other seven amino acid residues in C-terminus are hydrophobic. So, our results show that the C-terminal region of amyloid beta peptide (25-35) is buried in the membrane and assumes alpha-helical structure, whereas the N-terminal region is exposed to the solvent with a flexible structure. This structure is very similar to membrane-mediated structure of substance P previously reported. The three-dimensional structure of a non-neurotoxic mutant of amyloid beta peptide (25-35), where Asn27 is replaced by Ala, in lithium dodecyl sulfate micelles was also determined. The structure is similar to that of the wild type amyloid beta peptide (25-35) in the C-terminal region, but the N-terminal flexible region is different. The structural comparison of amyloid beta peptide (25-35), its non-neurotoxic mutant and substance P gives a structural basis to understand the mechanism of neurotoxicity caused by amyloid beta peptide.
Three-dimensional structures of the amyloid beta peptide (25-35) in membrane-mimicking environment.,Kohno T, Kobayashi K, Maeda T, Sato K, Takashima A Biochemistry. 1996 Dec 17;35(50):16094-104. PMID:8973180
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.