Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.23 (beta-galactosidase)
14,648 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 3.3-kilobase DNA complementary to human microtubule-associated protein 2 (MAP2) was sequenced by the dideoxy method. The 3' end terminates at an internal EcoRI site before the polyA tail. Due to the arrangement of the cDNA insert in the lambda gt11 vector, the MAP2 fragment is not fused to beta-galactosidase when expressed. The Chou Fasman algorithm for the initial 58 amino acids from the first in-frame methionine predicts an alpha helix. Beyond this point, a series of turns is predicted until amino acid 160. The frequent presence of basic residues in proximity to serines or threonines is consistent with multiple phosphorylation sites. The minimum specificity determinant for Ca2+/calmodulin-dependent kinase is repeated 13 times. The sequence of a region containing a MAP2 epitope that is shared with the Alzheimer neurofibrillary tangle was determined by DNase treatment of the cDNA and antibody selecting the small resultant clones in a lambda gt11 sublibrary. Likewise, a MAP2 epitope that is not shared with the neurofibrillary tangle also has been located. Both epitopes are in the projection portion of the molecule. A bovine MAP2 cyanogen bromide fragment, which contains the epitope shared with the neurofibrillary tangle, is partially insoluble under aqueous conditions, probably due to the aggregation of oppositely charged residues. Thus, rapid cleavage of MAP2 to small peptides is probably necessary in vivo to prevent the aggregation of larger cleavage fragments.
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PMID:Partial sequence of MAP2 in the region of a shared epitope with Alzheimer neurofibrillary tangles. 245 76

A new mouse monoclonal antibody was raised to a bacterial fusion protein between beta-galactosidase and the extracellular domain of the human amyloid protein precursor (APP). In immunoblotting experiments, this monoclonal antibody labelled the bacterial fusion protein used as an immunogen, the human brain APP, and different full-length APP isoforms expressed by transfected cells. In immunocytochemistry, the monoclonal antibody stained the dystrophic neurites of abundant senile plaques found in the cerebral cortex of patients with Alzheimer's disease. Using bacterial expression of several cDNA fragments, the epitope was mapped to an amino acid sequence of APP not investigated before.
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PMID:A new monoclonal antibody against the anionic domain of the amyloid precursor protein of Alzheimer's disease. 750 27

The kinetics of amyloid fibril formation by beta-amyloid peptide (Abeta) are typical of a nucleation-dependent polymerization mechanism. This type of mechanism suggests that the study of the interaction of Abeta with itself can provide some valuable insights into Alzheimer disease amyloidosis. Interaction of Abeta with itself was explored with the yeast two-hybrid system. Fusion proteins were created by linking the Abeta fragment to a LexA DNA-binding domain (bait) and also to a B42 transactivation domain (prey). Protein-protein interactions were measured by expression of these fusion proteins in Saccharomyces cerevisiae harboring lacZ (beta-galactosidase) and LEU2 (leucine utilization) genes under the control of LexA-dependent operators. This approach suggests that the Abeta molecule is capable of interacting with itself in vivo in the yeast cell nucleus. LexA protein fused to the Drosophila protein bicoid (LexA-bicoid) failed to interact with the B42 fragment fused to Abeta, indicating that the observed Abeta-Abeta interaction was specific. Specificity was further shown by the finding that no significant interaction was observed in yeast expressing LexA-Abeta bait when the B42 transactivation domain was fused to an Abeta fragment with Phe-Phe at residues 19 and 20 replaced by Thr-Thr (AbetaTT), a finding that is consistent with in vitro observations made by others. Moreover, when a peptide fragment bearing this substitution was mixed with native Abeta-(1-40), it inhibited formation of fibrils in vitro as examined by electron microscopy. The findings presented in this paper suggest that the two-hybrid system can be used to study the interaction of Abeta monomers and to define the peptide sequences that may be important in nucleation-dependent aggregation.
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PMID:Two-hybrid system as a model to study the interaction of beta-amyloid peptide monomers. 870 Aug 86

Gene therapy may be a useful means of delivering substances to the brain that are capable of preventing neuronal degeneration. In the present experiment, we determined whether intraparenchymal transplants of primary autologous cells genetically modified to produce nerve growth factor (NGF) would prevent injury-induced degeneration of cholinergic neurons. Cultured primary monkey fibroblasts were genetically modified to produce human NGF, and secreted 13.2 ng NGF/10(6) cells/h in vitro. Adult monkeys then underwent fornix transections to induce degeneration of basal forebrain cholinergic neurons, and received autologous grafts of either NGF-producing or control, beta-galactosidase-producing fibroblasts directly into the basal forebrain region. One month later, 61.7 +/- 8.9% of cholinergic neurons remained indentifiable in NGF-graft recipients compared to 26.2 +/- 5.0% in control graft recipients (P < 0.02). Neuronal protection correlated with the accuracy of graft placement: up to 92% protection from neuronal degeneration occurred when NGF-secreting grafts were accurately placed immediately adjacent to injured neurons. Thus, intraparenchymal NGF delivery to the adult primate brain by gene transfer can prevent the degeneration of basal forebrain cholinergic neurons. Gene therapy can target intraparenchymal brain sites for regionally specific neurotrophin delivery, thereby avoiding limitations imposed by diffusion of substances across the blood-brain barrier and through CNS parenchyma, while avoiding adverse effects of neurotrophic factors delivered in a non-directed manner to the central nervous system. The delivery of NGF by gene transfer to the brain merits further study as a means of preventing cholinergic neuronal degeneration in human disorders such as Alzheimer's disease.
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PMID:Gene therapy in the adult primate brain: intraparenchymal grafts of cells genetically modified to produce nerve growth factor prevent cholinergic neuronal degeneration. 873 62

Mutant presenilins cause Alzheimer's disease. Presenilins have multiple hydrophobic regions that could theoretically span a membrane, and a knowledge of the membrane topology is crucial for deducing the mechanism of presenilin function. By analyzing the activity of beta-galactosidase hybrid proteins expressed in C. elegans, we show that the C. elegans SEL-12 presenilin has eight transmembrane domains and that there is a cleavage site after the sixth transmembrane domain. We examine the presenilin sequence in view of the predicted topology and discuss possible mechanisms for presenilin function.
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PMID:Membrane topology of the C. elegans SEL-12 presenilin. 893 32

A fusion protein between beta-galactosidase and the amino-terminal domain of amyloid precursor protein (APP) was used as an immunogen for the production of monoclonal antibodies. One of these antibodies, the 5D12 monoclonal antibody, labeled the neurofibrillary tangles (NFT) by immunohistochemistry, as well as isolated paired helical filaments (PHF) in electron microscopy. In immunoassay, the ascitic fluid produced by the 5D12 clone was demonstrated to contain a high titer of antibodies to heat-stable microtubule associated proteins (MAPs). By immunoblotting, the proteins recognized in heat-stable MAPs were found to correspond to tau proteins. The 5D12 antibody recognized normal tau isolated from rat and human brain homogenates, and PHF-tau isolated from the brain of patients with Alzheimer's disease (AD). By immunoblotting, the 5D12 antibody also recognized the full-length recombinant tau protein but not the fusion protein used as an immunogen. The immunoreactivity of the 5D12 antibody with tau was completely abolished when the half-carboxy domain of tau, containing the tubulin-binding repeats, was removed. This study demonstrates that the use of the amino-terminal domain of APP as an immunogen led to the generation of a monoclonal antibody to the half-carboxy domain of tau.
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PMID:Generation of a monoclonal antibody to the carboxy-terminal domain of tau by immunization with the amino-terminal domain of the amyloid precursor protein. 897 5

Nerve growth factor therapy has been proposed as a potential means of preventing degeneration of basal forebrain cholinergic neurons in Alzheimer's disease and thereby improving cognition. However, NGF has been reported to upregulate expression of the beta-amyloid precursor protein, which in turn could accelerate deposition of "mature" beta-amyloid in the brain. To address this possibility, the brains of 16 adult and aged rhesus monkeys were examined for beta-amyloid plaque deposition in the presence or absence of NGF treatment. Six aged monkeys received intraparenchymal grafts into the cholinergic basal forebrain of autologous cells genetically modified to secrete NGF, six aged monkeys received intraparenchymal grafts of autologous control cells expressing the reporter gene beta-galactosidase, and four adult nonoperated monkeys served as additional controls. All brains were examined for expression of mature beta-amyloid using an antibody recognizing amino acids 1-40 of the beta-amyloid peptide. Amyloid plaques were systematically quantified in representative sections of the temporal, frontal, cingulate, insular, and parietal cortices and in the amygdala and hippocampus. Results disclosed that aging resulted in an increase in amyloid plaque formation: no plaques at all were detected in nonaged monkeys, whereas a mean of 20 +/- 13 plaques per section were present in control-aged monkeys. Aged subjects with intraparenchymal NGF-secreting grafts for 3 months contained a mean of 29 +/- 14 plaques per section, an amount that did not differ significantly from control-aged monkeys (P = 0.66). Thus, 3 months of intraparenchymal NGF delivery did not significantly increase beta-amyloid deposition.
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PMID:Targeted intraparenchymal delivery of human NGF by gene transfer to the primate basal forebrain for 3 months does not accelerate beta-amyloid plaque deposition. 987 92

We used adenoviral-mediated gene transfer of human amyloid precursor proteins (h-APPs) to evaluate the role of various h-APPs in causing neuronal cell death. We were able to infect PC12 cells with very high efficiency because approximately 90% of the cells were cytochemically positive for beta-galactosidase activity when an adenoviral vector containing LacZ cDNA was used to infect cells. Cells infected with adenovirus containing h-APP cDNA showed high-level transcription and expression of h-APP as measured by reverse transcriptase-polymerase chain reaction and Western immunoblot analyses, respectively. Intracellular and extracellular levels of h-APP were elevated approximately 17-and 24-fold in cultures infected with recombinant adenovirus containing wild-type mutant and 13- and 17-fold with V642F mutant. No elevation in h-APP was seen in cultures infected with antisense h-APP or null adenovirus. H-APP levels were maximal 3 days after infection. Overexpression of V642F mutant h-APP in PC12 cells and hippocampal neurons resulted in about a twofold increase in death compared with overexpression of wild-type h-APP. These results demonstrate the usefulness of recombinant adenoviral mediated gene transfer in cell culture studies and suggest that overexpression of a familial Alzheimer's disease mutant APP may be toxic to neuronal cells.
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PMID:Death of PC12 cells and hippocampal neurons induced by adenoviral-mediated FAD human amyloid precursor protein gene expression. 1008 85

Forced overexpression of wild-type Alzheimer amyloid precursor protein (APP) causes postmitotic neurons to degenerate. Caspase-3 (CPP32) is a principal cell death protease involved in neuronal apoptosis during physiological development and under pathological conditions. Here, we investigated whether APP overexpression activates caspase-3 in human postmitotic neurons using adenovirus-mediated gene transfer. When a recombinant adenovirus vector expressing human wild-type APP695 was infected in vitro into neurally differentiated embryonal carcinoma NT2 cells, only postmitotic neurons underwent severe degeneration. Before neurodegeneration, full-length APP- and Abeta-immunoreactive peptides were accumulated in infected neurons, and caspase-3-like protease activity was markedly elevated. Western blot analysis revealed that activated caspase-3 subunits were generated in APP-accumulating neurons. Such neuronal caspase-3 activation was undetectable in NT2 neurons infected with beta-galactosidase-expressing adenovirus. Addition of the caspase-3 inhibitor acetyl-Asp-Glu-Val-Asp-aldehyde to the culture medium significantly reduced the severity of degeneration exhibited by APP-overexpressing neurons. Immunocytochemical analyses revealed that some APP-accumulating neurons contained activated caspase-3 subunits and exhibited the characteristics of apoptosis, such as chromatin condensation and DNA fragmentation. Activation of caspase-3 was also observed in vivo in rat hippocampal neurons infected with the APP-expressing adenovirus. These results suggest that wild-type APP is an intrinsic activator of caspase-3-mediated death machinery in postmitotic neurons.
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PMID:Activation of neuronal caspase-3 by intracellular accumulation of wild-type Alzheimer amyloid precursor protein. 1043 52

Protein misfolding is the basis of a number of human diseases and presents an obstacle to the production of soluble recombinant proteins. We present a general method to assess the solubility and folding of proteins in vivo. The basis of this assay is structural complementation between the alpha- and omega- fragments of beta-galactosidase (beta-gal). Fusions of the alpha-fragment to the C terminus of target proteins with widely varying in vivo folding yield and/or solubility levels, including the Alzheimer's amyloid beta (A beta) peptide and a non-amyloidogenic mutant thereof, reveal an unambiguous correlation between beta-gal activity and the solubility/folding of the target. Thus, structural complementation provides a means of monitoring protein solubility/misfolding in vivo, and should find utility in the screening for compounds that influence the pathological consequences of these processes.
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PMID:Protein solubility and folding monitored in vivo by structural complementation of a genetic marker protein. 1117 20


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