Inhibition of beta A4 production by specific modulation of beta-secretase activity.

To study amyloid precursor protein (APP) processing we expressed different APP isoforms with and without the Swedish mutation and the membrane inserted C-terminal 100 residues of APP (SPA4CT) in the human neuroblastoma cell line SY5Y. We show that expression of the Swedish mutation results in a significant production of the amyloidogenic intermediate A4CT, which is further processed by gamma-secretase leading to an overproduction of beta A4. Treatment with methylamine and ammonium chloride, inhibitors interfering with intracellular transport mechanisms, inhibits beta-secretase activity without influencing the physiological APP cleavage by alpha-secretase activity.

APP gene family: unique age-associated changes in splicing of Alzheimer's betaA4-amyloid protein precursor.

The betaA4-amyloid protein precursor (APP) is a transmembrane glycoprotein that is the source of the characteristic betaA4-amyloid deposits of Alzheimer brains. It exists in eight isoforms generated by alternative splicing of exons 7, 8 and 15, of which the L-APP mRNAs lacking exon 15 are significantly expressed in non-neuronal cells and tissues, but not in neurones. Recently, it was shown that APP is a member of a multigene family of which the amyloid precursor-like protein 2 (APLP2) is the nearest relative.

[Apolipoprotein E and Alzheimer dementia. Personal results and brief literature review].

The apolipoprotein E allele (Apo-E gene) status was determined in 147 individuals from a longitudinal study. 53 satisfied NINCDS-ADRDA criteria for probable or possible Alzheimer's disease (AD), 37 were non-demented healthy controls. 31 patients with AD had one or two Apo-E 4 alleles (phenotypes 1 x 4-2; 20 x 4-3; 10 x 4-4) compared with only 9 controls (8 x 4-3; 1 x 4-4).

Complete nucleotide and deduced amino acid sequence of rat amyloid protein precursor-like protein 2 (APLP2/APPH): two amino acids length difference to human and murine homologues.

We present the cDNA sequence of the rat amyloid precursor-like protein 2 (APLP2) comprising the complete coding sequence of 765 amino acid residues. By alternative splicing of two exons, transcripts encoding for 753, 709 and 697 amino acids are also generated. The derived amino acid sequence displays a sequence identity to human APLP2 of approx.

Rapid induction of Alzheimer A beta amyloid formation by zinc.

A beta 1-40, a major component of Alzheimer's disease cerebral amyloid, is present in the cerebrospinal fluid and remains relatively soluble at high concentrations (less than or equal to 3.7 mM). Thus, physiological factors which induce A beta amyloid formation could provide clues to the pathogenesis of the disease.

Amyloid precursor protein secretion and beta A4 amyloid generation are not mutually exclusive.

The cellular factors regulating the generation of beta A4 from the amyloid precursor protein (APP) are unknown. Protein phosphorylation by protein kinase C (PKC) has been found to influence the processing and metabolism of APP. In this report, we show that in the human neuroblastoma cell line SY5Y, beta A4 generation from full-length APP is not changed by PKC activation whereas production of the non-amyloidogenic secretory fragment (APPsec) and of the C-terminal fragment of beta A4 (p3) are stimulated.

Membrane-associated forms of the beta A4 amyloid protein precursor of Alzheimer's disease in human platelet and brain: surface expression on the activated human platelet.

The amyloid protein precursor (APP) of Alzheimer's disease (AD) is abundantly expressed in platelets, where its primary function remains undetermined. As an integral transmembrane protein, the release of APP from the membrane may be a critical event in AD. We examined the association of APP with human platelet membranes using a combination of alkali treatment and immunoprecipitation of the carboxyl-terminus of APP.

Secretion of nerve growth factor from septum stimulates neurite outgrowth and release of the amyloid protein precursor of Alzheimer's disease from hippocampal explants.

Alzheimer's disease (AD) is characterized by the deposition of amyloid in the extracellular and intracellular compartments of the cerebral cortex. The extracellular amyloid consists of a protein (beta A4) which is derived from a larger precursor, the amyloid protein precursor (APP). Several studies have implicated APP in the regulation of neurite outgrowth during development, although the precise function of APP remains unknown.

Similar alternative splicing of a non-homologous domain in beta A4-amyloid protein precursor-like proteins.

The beta A4-amyloid protein precursor (APP) is a transmembrane glycoprotein that is the source of the characteristic beta A4-amyloid deposits found in Alzheimer brains. It is expressed in several isoforms generated by alternative splicing of exons 7, 8, and 15, of which the leukocyte-derived APP mRNAs lacking exon 15 are significantly expressed in non-neuronal tissues, but not in neurons. The recent finding of APP-like proteins prompted us to analyze alternative splicing of the nearest relative of APP, the amyloid protein precursor homologue (APPH) or amyloid precursor-like protein 2 (APLP2).

Transforming growth factor beta mediates increase of mature transmembrane amyloid precursor protein in microglial cells.

By using the immortalized microglial cell line BV-2, we show that the high expression of the beta A4 amyloid precursor protein (APP), its biogenesis and metabolism is modulated by TGF beta, a cytokine with immunosuppressive activity, and by the microglia-stimulating agent LPS. TGF beta induces accumulation of cellular mature APP, the putative precursor of the amyloid subunit of Alzheimer's disease. LPS leads to an increase in cellular immature, non-amyloidogenic APP and secretion of also non-amyloidogenic APP fragments.

A heparin-binding domain in the amyloid protein precursor of Alzheimer's disease is involved in the regulation of neurite outgrowth.

The amyloid protein precursor (APP) of Alzheimer's disease is synthesized as an integral transmembrane protein that is released from cells in culture following proteolytic cleavage. The function of released APP is not known, although there is evidence that the protein may bind to components of the extracellular matrix (ECM). In the present study, substratum-bound APP stimulated neurite outgrowth in cultures of chick sympathetic and mouse hippocampal neurons.

Synaptophysin immunoreactivity of the cortical neuropil in vascular dementia of Binswanger type compared with the dementia of Alzheimer type and nondemented controls.

It has been shown recently that in Alzheimer's disease the degree of dementia is strongly correlated with a reduction of the synaptophysin reactivity of the cortical neuropil as a measure of synapse density, while counts of neuritic plaques showed a weak correlation. This suggests that mechanisms acting at the synaptic level, finally resulting in a numerical decline of synapses, may represent an important factor in the pathogenesis of dementia. Under these aspects, we wanted to examine whether changes of synaptophysin immunoreactivity may also occur in dementia of vascular origin such as Binswanger's disease, where the white matter atrophy is usually conceived to be the main morphologic correlate of dementia.

Beta A4-amyloid protein precursor mRNA isoforms without exon 15 are ubiquitously expressed in rat tissues including brain, but not in neurons.

The beta A4-amyloid protein precursor (APP), the source of the beta A4-amyloid deposits found in Alzheimer brains, constitutes a family of transmembrane glycoproteins generated by alternative splicing. While exon 7 and exon 8 are well known to be alternatively spliced, APP mRNA isoforms without exon 15 were only recently identified in leukocytes and rat brain microglial cells and therefore denoted as L-APP mRNAs. In order to perform a detailed analysis of individual L-APP mRNA isoforms in perfused rat tissues, we developed a quantitative polymerase chain reaction assay from reverse transcribed RNA allowing us to analyze the alternatively spliced region in between exon 6 and 16.

Apolipoprotein E-4 gene dose in clinically diagnosed Alzheimer's disease: prevalence, plasma cholesterol levels and cerebrovascular change.

The prevalence of the apolipoprotein E-4 allele (ApoE-4) was significantly higher in a referral population of 40 patients with clinically diagnosed Alzheimer's disease than in a sample of non-demented elderly controls (P < 0.01). The highest plasma cholesterol levels were found in demented patients homozygotic for Apo E-4, but no significant increases of glucose, triglycerides and thyroxine or of leuko-araiosis and brain infarcts were verified in this preliminary study.

Alzheimer's disease and transgenic mice.

Transgenic mice overexpressing the three major neuronal isoforms of the human amyloid precursor protein (APP), APP695, APP751, APP770 may provide an animal model for the analysis of the mechanisms and risk factors leading to amyloid deposition in Alzheimer's disease (AD) and Downs syndrome (DS). We have therefore generated transgenic mice expressing these isoforms under the control of the strong metallothionin promoter. Although we can demonstrate expression of transgenic APP in several tissues including brain, expression levels never exceeded those of the endogenous mouse APP.

Amyloid-like properties of peptides flanking the epitope of amyloid precursor protein-specific monoclonal antibody 22C11.

Alzheimer's disease is one of the prevalent forms of human dementia. Its pathology is distinguished by proteinaceous deposits ("amyloid") in the brain. They contain a peptide (beta A4) that is proteolytically derived from a larger transmembrane protein.

Drosophila proteasome Dm25 subunit substitutes the mouse MC3 subunit in hybrid proteasomes. The N-terminal domain is essential for subunit incorporation.

The proteasome is a multisubunit 20 S proteinase complex involved in ubiquitin-dependent and -independent intracellular protein metabolism. Individual subunits of the alpha- and beta-type share extensive sequence homology and are encoded as members of two related and evolutionarily conserved gene families. Due to the lack of viable deletion mutants of essential alpha-type proteasome subunits in higher eukaryotes, an identification and analysis of potentially homologous subunits of different species was so far not possible.

APP+ T lymphocytes selectively sorted to endomysial tubes in polymyositis displace NCAM-expressing muscle fibers.

The characteristic pathogenic feature of polymyositis (PM) is muscle invasion by T lymphocytes penetrating the basal lamina and displacing the sarcolemma of normal muscle fibers (T cell invasion of endomysial tubes). Active forward movement of these T cells is indicated by cell extensions interdigitating with the muscle fiber surface. Here we describe for the first time high abundance of Alzheimer amyloid protein precursor (APP) in invasive T cells contacting the border of muscle fibers in PM.

Generation of beta A4 from the amyloid protein precursor and fragments thereof.

The cellular mechanisms underlying the generation of beta A4 in Alzheimer's disease and its relationship to the normal metabolism of the amyloid protein precursor (APP) are unknown. In this report, we show that expression of the C-terminal 100 residues of APP, with (SPA4CT) or without (A4CT) a signal sequence in the N-terminal position, in human neuroblastoma cells results in secretion of a 4 kDa beta A4-like peptide. In A4CT and SPA4CT expressing SY5Y cells, beta A4 generation could not be inhibited by the lysosomotropic amines chloroquine and ammonium chloride but was inhibited by brefeldin A, monensin and methylamine.

APP expression in primary neuronal cell cultures from P6 mice during in vitro differentiation.

Primary neuronal cell cultures from P6 mice were investigated in order to study amyloid protein precursor (APP) gene expression in differentiating neurons. Cerebellar granule cells which strongly express APP 695 allowed the identification of three distinct isoforms of neuronal APP 695. The high-molecular-weight form of APP 695 is sialylated.