Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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The amyloid precursor protein (APP) is a glycoprotein consisting of at least four isoforms derived from a single gene by a process of alternative splicing. The membrane-bound forms of APP have been suggested to have adhesive properties and to mediate neural cell adhesion. Previous studies have demonstrated the ability of Fab' fragments of antibodies to extracellular domains of APP to inhibit neural cell binding to a collagen substrate, suggesting a physiological role for the collagen-binding properties of APP. The binding of APP has been demonstrated to be specific for type IV collagen, and no binding to other extracellular matrix components, including fibronectin and laminin, was detected. The APP-collagen binding appeared to be mediated by a heparin-bridge mechanism, since the binding was abolished by the addition of excess heparan or heparinase. These results were observed by both a homogenate-collagen binding assay and a cell-surface adhesion assay, thus providing further evidence for the adhesion role of APP. They also pose the question of the possible role of the heparin-binding properties of APP in the genesis of the neuritic plaques characteristic of Alzheimer's disease.
Mol Chem Neuropathol
PMID:APP-collagen interaction is mediated by a heparin bridge mechanism. 152 Apr

Platelet MAO-B activity, serum vitamin B12 levels, and plasma folate were measured in patients suffering from presenile (AD) and senile (SDAT) dementia of Alzheimer-type, and vascular dementia (VD). MAO-B was higher in the SDAT group than in AD and controls. An inverse relationship between MAO-B activity and vit. B12 levels was documented in the whole group and in each category studied; furthermore, MAO-B was positively related to age. All the patients were then divided into two groups, according to vit. B12 levels (Group I: less than 200 pg/mL; Group II: greater than or equal to 200 pg/mL); Group I showed a significantly higher MAO-B activity with respect to Group II. The results indicate the existence of a negative association between platelet MAO-B activity and serum levels of vitamin B12 and confirm the existence of biological differences between presenile and senile dementia of Alzheimer type.
Mol Chem Neuropathol
PMID:Platelet MAO-B activity and vitamin B12 in old age dementias. 152 Apr 4

Viruses have the capacity to induce alterations and degenerations of neurons by different direct and indirect mechanisms. In the review, we have focused on some examples that may provide new avenues for treatment or altering the course of infections, i.e., antibodies to fusogenic virus membrane proteins, drugs that interfere with lipid metabolism, calcium channel blockers, immunoregulatory molecules, and, and inhibitors of excitotoxic amino acids. Owing to their selectivity in attack on regions of nervous tissue, governed by viral factors and by routes of invasion, viral receptors or metabolic machineries of infected cells, certain viral infections show similarities in distribution of their resulting lesions in the nervous system to that of the common human neurodegenerative diseases (namely, motor neurons disease, Parkinson's disease, and Alzheimer's disease). However, it should be emphasized that no infectious agent has as yet provided a complete animal model for any of these diseases, nor has any infectious agent been linked to them from observations on clinical or postmortem materials.
Mol Chem Neuropathol
PMID:Potential role of viruses in neurodegeneration. 152 Apr 6

This paper examines inhibition of acetylcholinesterase (AchE) and butyrylcholinesterase (BuchE) by tetrahydroaminoacridine (THA), an acridine analog under consideration for palliative treatment of Alzheimer's dementia. THA causes linear mixed inhibition of AchE hydrolysis of acetylthiocholine, a cationic substrate (KI = 3.8 x 10(-9) M), and linear competitive inhibition of AchE hydrolysis of 7-acetoxy-4-methylcoumarin, an uncharged substrate (KI = 6.8 x 10(-9) M), and N-methyl-7-dimethylcarbamoxyquinolinium, a cationic carbamate (KI = 1.5 x 10(-8) M). Propidium association with AchE in the presence of saturating concentrations of THA is characterized by a dissociation constant of 7.7 +/- 0.7 x 10(-6) M, a value within 2-fold of the dissociation constant in the absence of THA. Association of THA with AchE is, therefore, not mutually exclusive with association of propidium at the peripheral anionic site. Moreover, THA causes dissociation of decidium complexes with AchE at concentrations compatible with a dissociation constant of 7.0 +/- 0.4 x 10(-9) M. Similar relationships were observed for THA inhibition of BuchE hydrolysis of butyrylthiocholine (KI = 2.5 x 10(-8) M) and dissociation of decidium complexes with BuchE (KD = 1.9 +/- 0.1 x 10(-8) M). These kinetic and equilibrium data uniformly indicate that THA associates with AchE and BuchE with high affinity and that the subsequent inhibition comes about through ligand association at the active center rather than at a peripheral site. The noncompetitive component of inhibition reflects association of THA with the acyl-enzyme intermediate, with subsequent effects on the rate of deacylation.
Mol Pharmacol 1992 Feb
PMID:Interaction of tetrahydroaminoacridine with acetylcholinesterase and butyrylcholinesterase. 153 17

The NF-M subunit of human neurofilaments has a C-terminal repeating 13-mer sequence. The 13-mer (Lys-Ser-Pro-Val-Pro-Lys-Ser-Pro-Val-Glu-Glu-Lys-Gly) (NF-M13) and 17-mer (Glu-Glu-Lys-Gly)-(NF-M13) sequences were synthesized, as were both the mono- and diphosphorylated Ser species. Circular dichroism (c.d.) studies and c.d. titrations with Al3+ and Ca2+ were performed. The conformation of the phosphorylated and unphosphorylated material was random in water. Deconvolution of the c.d. spectra, in trifluoroethanol, of the untitrated samples yielded a high content of unordered structure, similar to the poly-L-proline II structure. Titration of the phosphorylated species with Al3+ or Ca2+ caused a surprising conformational change to occur, yielding a high content of beta-pleated sheet structure. A mechanism of metal binding to the phosphofragments is proposed which may be relevant to the formation of neurofibrillary tangles in Alzheimer's disease.
J Mol Biol 1992 Feb 05
PMID:Metal ion-induced conformational changes of phosphorylated fragments of human neurofilament (NF-M) protein. 154 14

In a previous report, we demonstrated in vivo ameliorating effects of conjugated estrogen in women suffering from senile dementia-Alzheimer's type. To investigate the effects of estrogen on the growth of cholinergic neurons, the present study was performed using rat cholinergic tissue implanted into the anterior chamber of the eye. Fetal diagonal band tissue containing cholinergic neurons was grafted into the anterior eye chamber of adult female rats that had either been treated or not with 2 mg estradiol valerate injected every 3 days after oophorectomy. Two and four weeks after transplantation, the axonal and/or dendritic growth of cholinergic neurons in the graft was studied using acetylcholinesterase histochemistry. At both times, acetylcholinesterase positive processes were densely distributed in the grafts of estradiol valerate treated rats, while in rats without estradiol valerate treatment acetylcholinesterase positive reaction was essentially localized only on the cell bodies. These findings were more obvious at 2 weeks after transplantation than at 4 weeks. These results suggest that estrogen acts on cholinergic neurons as a growth factor.
J Steroid Biochem Mol Biol 1992 Mar
PMID:Estrogen as a growth factor to central nervous cells. Estrogen treatment promotes development of acetylcholinesterase-positive basal forebrain neurons transplanted in the anterior eye chamber. 156 34

2,4-Diaminotoluene (2,4-DAT), a high volume synthetic compound, is moderately carcinogenic to rodents. We report here that 2,4-DAT is a substrate for the peroxidase activity of prostaglandin H synthase (PHS). In contrast to many aromatic amines which are activated as mutagens by PHS, we find that 2,4-DAT is not mutagenic to six S. typhimurium strains with this activation system. The strains tested include YG1006, YG1024, and YG1029, which are far more sensitive to the mutagenicity of aromatic amines and nitroarenes than are the standard tester strains. Although not mutagenic itself, 2,4-DAT does enhance the mutagenicity of 2-aminofluorene (2-AF) in the PHS-catalyzed system in strains TA98, YG1006, and YG1024, with maximal enhancement of 140%, 1831%, and 1216%, respectively. Half-maximal enhancement of 2-AF mutagenicity is observed at 15-20 microM 2,4-DAT for strains YG1006 and YG1024, and about 80 microM for TA98. Studies with compounds structurally related to 2,4-DAT revealed enhancement of 2-AF mutagenicity with 2,5-DAT and o-phenylenediamine (o-PD) but not for other DAT isomers, toluidines, and phenylenediamines. Maximal enhancement of 2-AF mutagenicity observed in TA98 with PHS-catalyzed activation was 110% for o-PD and 60% for 2,5-DAT. This comutagenic effect of 2,4-DAT appears quite specific for 2-AF, as it fails to enhance either the PHS-dependent mutagenicity of the aromatic amines benzidine and 2-naphtylamine, or the direct mutagenicity of N-acetoxy-acetylaminofluorene,2-nitrofluorene,4- nitroquinoline-N-oxide and 1,1,1-trichloropropene-2,3-oxide. Enhancement of 2-AF mutagenicity by 2,4-DAT is also observed with cytochrome P-450-dependent activation, however the half-maximal 2,4-DAT concentration was 400 microM, and the maximal enhancement was only 50%. The ability of 2,4-DAT, under conditions where it is not itself mutagenic, to enhance the genotoxicity of the potent carcinogen 2-AF comprises an intriguing toxicological interaction, and underscores the inherent difficulties in assessing the genotoxic risks posed by mixtures of compounds.
Environ Mol Mutagen 1992
PMID:Prostaglandin H synthase-dependent genotoxicity of 2,4-diaminotoluene. 157 43

The Kunitz-type protease inhibitor is one of the serine protease inhibitors. It is found in blood, saliva, and all tissues in mammals. Recently, a Kunitz-type sequence was found in the protein sequence of the amyloid beta precursor protein (beta APP). It is known that beta APP accumulates in the neuritic plaques and cerebrovascular deposits of patients with Alzheimer's disease. Collagen type VI in chicken also has an insertion of a Kunitz-type sequence. To elucidate the evolutionary origin of these insertion sequences, we constructed a phylogenetic tree by use of all the available sequences of Kunitz-type inhibitors. The tree shows that the ancestral gene of the Kunitz-type inhibitor appeared about 500 million years ago. Thereafter, this gene duplicated itself many times, and some of the duplicates were inserted into other protein-coding genes. During this process, the Kunitz-type sequence in the present beta APP gene diverged from its ancestral gene about 270 million years ago and was inserted into the gene soon after duplication. Although the function of the insertion sequences is unknown, our molecular evolutionary analysis shows that these insertion sequences in beta APP have an evolutionarily close relationship with the inter-alpha-trypsin inhibitor or trypstatin, which inhibits the activity of tryptase, a novel membrane-bound serine protease in human T4+ lymphocytes.
J Mol Evol 1992 Jun
PMID:Evolutionary origin of a Kunitz-type trypsin inhibitor domain inserted in the amyloid beta precursor protein of Alzheimer's disease. 159 45

The A4 or beta-peptide (39 to 43 amino acid residues) is the principal proteinaceous component of amyloid deposits in Alzheimer's disease. Using circular dichroism (c.d.), we have studied the secondary structures and aggregational properties in solution of 4 synthetic amyloid beta-peptides: beta-(1-28), beta-(1-39), beta-(1-42) and beta-(29-42). The natural components of cerebrovascular deposits and extracellular amyloid plaques are beta-(1-39) and beta-(1-42), while beta-(1-28) and beta-(29-42) are unnatural fragments. The beta-(1-28), beta-(1-39) and beta-(1-42) peptides adopt mixtures of beta-sheet, alpha-helix and random coil structures, with the relative proportions of each secondary structure being strongly dependent upon the solution conditions. In aqueous solution, beta-sheet structure is favored for the beta-(1-39) and beta-(1-42) peptides, while in aqueous solution containing trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP), alpha-helical structure is favored for all 3 peptides. The alpha-helical structure unfolds with increasing temperature and is favored at pH 1 to 4 and pH 7 to 10; the beta-sheet conformation is temperature insensitive and is favored at pH 4 to 7. Peptide concentration studies showed that the beta-sheet conformation is oligomeric (intermolecular), whereas the alpha-helical conformation is monomeric (intramolecular). The rate of aggregation to the oligomeric beta-sheet structure (alpha-helix----random coil----beta-sheet) is also dependent upon the solution conditions such as the pH and peptide concentration; maximum beta-sheet formation occurs at pH 5.4. These results suggest that beta-peptide is not an intrinsically insoluble peptide. Thus, solution abnormalities, together with localized high peptide concentrations, which may occur in Alzheimer's disease, may contribute to the formation of amyloid plaques. The hydrophobic beta-(29-42) peptide adopts exclusively an intermolecular beta-sheet conformation in aqueous solution despite changes in temperature or pH. Therefore, this segment may be the first region of the beta-peptide to aggregate and may direct the folding of the complete beta-peptide to produce the beta-pleated sheet structure found in amyloid deposits. Differences between the solution conformations of the beta-(1-39) and beta-(1-42) peptides suggests that the last 3 C-terminal amino acids are crucial to amyloid deposition.
J Mol Biol 1992 Jun 20
PMID:Solution conformations and aggregational properties of synthetic amyloid beta-peptides of Alzheimer's disease. Analysis of circular dichroism spectra. 161 91

Alzheimer's Disease (AD), a disorder of unknown etiology, is the most common form of adult-onset dementia and is characterized by severe intellectual deterioration. The definitive diagnosis of AD is made by postmortem examination of the brain, which reveals large quantities of neurofibrillary tangles (NFT) and senile plaques within the parenchyma. The NFT are composed of paired helical filaments associated with several cytoskeletal proteins. The primary protein component of senile plaques is beta/A4 amyloid, a 42-43 amino acid peptide derived from a much larger molecule, the amyloid precursor protein (APP). Vascular beta/A4 amyloidosis is also prevalent in the disease. The mechanism by which beta/A4 amyloid accumulates in the AD brain is unknown. Recent research has demonstrated that the precursor molecule, APP, is a transmembrane protein with a large extracytoplasmic domain, a membrane spanning region that includes the portion that gives rise to beta/A4 amyloid, and a short intracytoplasmic domain. The precursor has multiple forms among which are those that differ by a variable length insert within the extracytoplasmic domain. The insert has sequence homology to the family of Kunitz protease inhibitor proteins. Cellular and animal models have been developed to study the nature of APP processing and the biological and behavioral consequences of beta/A4 amyloidosis. The results of such studies indicate that the normal processing of APP involves enzymatic cleavage of the molecule within the beta/A4 amyloid region, thus preventing the accumulation of beta/A4 in the normal brain. The factors leading to abnormal processing of APP, and consequent beta/A4 amyloid accumulation within the AD brain, have yet to be identified. In cell culture, the biological effects associated with beta/A4 amyloid include neurotrophic and neurotoxic activities, while the peptide has also been shown to have dramatic behavioral effects in animal models.
J Mol Neurosci 1992
PMID:Molecular and cellular biology of Alzheimer amyloid. 162 58


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