Production of Alzheimer 4kDa beta-amyloid peptide requires the C-terminal cytosolic domain of the amyloid precursor protein

Amyloid precursor protein (APP) is metabolized through at least three pathways: the constitutive secretory pathway, the endosomal-lysosomal pathway and the 4-kDa A beta-producing pathway. The 4-kDa A beta (4 kDa A beta)-producing pathway which may play a primary role in the pathogenesis of Alzheimer's disease (AD) is presently unknown. In the present paper, we examine the production of the 4 kDa A beta in K562 lymphoid cells transfected with a truncated APP695 construct (APP delta 652-695) encoding an APP which lacks the cytosolic C-terminal domain except the four N-terminal amino acids, KKKQ. The APP delta 652-695-transfected cells (APP delta 652-695 cells) do not secrete 4 kDa A beta compared to APP 695-transfected cells (APP695 cells). Moreover, while the APP delta 652-695 and APP695 cells secrete equivalent levels of sAPP, the APP delta 652-695 cells accumulate less APP intracellularly than the APP695 cells. These results reveal that in the K562 cells (1), the last 43 amino acid residues at the C-terminus of APP are important in targeting APP through the 4 kDa A beta producing pathway and (2) processing of APP into 4 kDa A beta is independent of the known secretase pathway.

Familial progressive subcortical gliosis

We report clinical and pathologic findings from two kindreds afflicted with a familial form of progressive subcortical gliosis. The disorder segregated as an autosomal dominant trait. Onset was in the presenium and the course was slowly progressive. Affected individuals initially manifested personality change, degeneration of social ability, disinhibition, psychotic symptoms, memory impairment, or depression. Later, all developed progressive dementia, frequently associated with verbal stereotypy, decreased speech output, echolalia, or manifestations of the human Klüver-Bucy syndrome. Terminal clinical manifestations included profound dementia, frequently with mutism, dysphagia, and extrapyramidal signs. Autopsy of seven end-stage patients revealed generalized cerebral atrophy, predominantly involving the white matter of the frontal and temporal lobes. Microscopically, prominent fibrillary astrocytosis was present in the subcortical white matter and in the subpial and deep layers of the overlying cerebral cortex. These changes were most pronounced in the frontal and temporal lobes, especially in the cingulate gyri and insulae. Mild cortical neuronal loss accompanied the gliosis, but no myelin loss was evident. The claustra and substantia nigra also showed severe astrocytosis and degenerative changes. Amyloid deposits and neuronal cytoskeletal inclusions were absent.

Creutzfeldt-Jakob disease and cerebral amyloid angiopathy

An 83-year-old female with no personal or familial neurological history developed progressive gait and speech disturbance and left motor deficit. She suffered intractable seizures and died 3 months after the onset of neurological signs. Neuropathology showed severe spongiosis and gliosis in the cortex and basal ganglia, and diffuse cerebral amyloid angiopathy. Immunostaining for prion protein (PrP) showed intense PrP positivity in areas of confluent spongiosis and some granular staining in astrocytes. The cortical vessel walls stained positively for beta/A4 amyloid but not for PrP amyloid. Both types of amyloid were only observed in pericapillary parenchyma, in areas with severe spongiosis. There were only a few tangles and neuritic plaques in the temporal cortex; amyloid plaques were not present either by silver stains or immunostains. There was neither arteriopathic leukoencephalopathy nor cerebral hemorrhage. Immunoblot analysis of brain extracts revealed an abnormal proteinase K-resistant isoform of PrP. Association of Creutzfeldt-Jakob disease and Cerebral amyloid angiopathy in the absence of Alzheimer changes in unusual. The association of PrP and beta/A4 amyloid deposits could have been fortuitous in an 83-year-old patient. An etiopathogenic relationship between beta/A4 amyloid deposition and PrP accumulation may also be considered.

Soluble amyloid beta-protein is a marker of Alzheimer amyloid in brain but not in cerebrospinal fluid

The amyloid beta protein (A beta), a 4 kD fragment of the beta amyloid precursor protein, is deposited as insoluble amyloid in the brain of Alzheimer disease (AD) subjects. Soluble A beta is a normal metabolic product and is present in cerebrospinal fluid. We identified soluble A beta forms of 4kD, 3kD and 3.7kD in AD but not in control brains free of amyloid deposits. All three forms of soluble A beta extend beyond residue 40. Analysis of cerebrospinal fluid from the same subjects confirmed the presence of only 4kD A beta in comparable amounts in AD and controls. The presence of soluble A beta only in brain regions with amyloid suggests they are related. The undetectability of soluble A beta in control brains indicates that it is normally removed or bound to other proteins. Failure of this protective mechanism might cause amyloid formation in AD.

Diurnal blood pressure variation and hormonal correlates in fatal familial insomnia

Fatal familial insomnia is a prion disease in which a selective thalamic degeneration leads to total sleep deprivation, hypertension, dysautonomia, adrenal overactivity, and impaired motor functions. With patients under continuous recumbency and polysomnographic control, we assessed the changes in the 24-hour patterns of blood pressure, heart rate, plasma catecholamines, corticotropin, and serum cortisol in three patients at different stages of the disease. Six healthy volunteers were used as control subjects. A dominant 24-hour component was detected at rhythm analysis of all variables, both in patients and control subjects. In the patients, the amplitudes gradually decreased as the disease progressed, leading to the obliteration of any significant dirunal variation only in the preterminal stage. A shift in phase corresponded to the loss of the nocturnal fall in blood pressure in an early stage of the disease, when nocturnal bradycardia was still preserved. Plasma cortisol was high and became increasingly elevated, whereas corticotropin remained within normal levels; abnormal nocturnal peaks appeared in their circadian patterns. The disrupted patterns of cortisol and blood pressure preceded the development of hypertension and severe dysautonomia, which in turn were paralleled by increasing catecholamine and heart rate levels. Our data demonstrate that in patients with fatal familial insomnia the changes detectable in the rhythmic component of diurnal blood pressure variability result in a pattern of secondary hypertension. Disturbances in thalamic, pituitary-adrenal, and autonomic functions seem to be involved in mediating these changes.

Progressive disruption of the circadian rhythm of melatonin in fatal familial insomnia

Fatal familial insomnia (FFI) is a disease characterized by loss of sleep activity due to selective thalamic degeneration. To assess the secretory pattern of melatonin (MT) in FFI, we studied two cases of overt disease under standardized conditions and polysomnographic control. Each patient underwent repeated 24-h study sessions, and MT was assayed at 30-min intervals. Six healthy volunteers were used as controls. Slow wave sleep was never recorded, whereas occasional episodes of enacted dreaming accompanied by rapid ocular movements and complex muscular activities were documented, with no detectable rhythm. Plasma MT concentrations gradually decreased as the disease progressed. A significant circadian rhythm was detected in the earlier recordings, with decreasing amplitudes with disease progression. Complete rhythm obliteration was achieved in the most advanced stage. Normally placed nocturnal acrophases were detected in the earlier stages, but then a shift toward the daytime hours was observed. Thalamic lesions of FFI appear to determine a progressive disruption of the sleep/wake cycle accompanied by decreased circulating levels of MT, with progressive alterations in the circadian rhythm of this hormone. On the other hand, decreased secretion of MT may contribute to the sleep disturbances of FFI.

Amyloid beta precursor protein and ubiquitin epitopes in human and experimental dystrophic axons. Ultrastructural localization

Dystrophic axons (DA) represent a major pathological feature of several neurodegenerative disorders, including infantile neuroaxonal dystrophy (INAD) and Alzheimer disease. We have previously presented evidence that amyloid beta precursor protein (BPP) and ubiquitin (Ub) are present in DA of different origin. We have now characterized the immunoreactivity of DA experimentally induced in rat by the administration of parabromophenylacetylurea (BPAU) and examined the subcellular localization of Ub and BPP in BPAU-induced DA and in DA present in subjects affected by INAD. BPAU-induced DA strongly immunoreacted with antisera to Ub and to COOH- and NH2-terminal regions of BPP. Immunoblots of DA-enriched brain regions were consistent with an increase in the amount of Ub and BPP in DA. Moreover, BPAU-induced DA immunoreacted with antibodies to PGP 9.5, a neuronal-specific Ub COOH-terminal hydrolase, and to the inducible heat shock protein 70. Antigenic characterization also indicated that the tubulovesicular membranes within DA derived largely from the smooth endoplasmic reticulum rather than from the Golgi system or the synaptic vesicles. Subcellular immunolocalization of Ub and BPP in both INAD- and BPAU-induced DA revealed that Ub and BPP colocalize in granulovesicular material in both conditions. In INAD DA intense Ub immunoreactivity was also detected in nonmembranous electron dense structures that were present only in these DA, probably because of the chronic course of INAD. Although BPP immunostaining may be related to accumulation of BPP-containing membranes in DA, Ub immunostaining is likely to result from activation of the Ub system by the neuron in the attempt to remove excessive and possibly abnormal proteins. A similar pathogenesis can be postulated for DA of Alzheimer disease.

[18F]FDG PET in fatal familial insomnia: the functional effects of thalamic lesions

We used [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) and positron emission tomography (PET) to study regional cerebral glucose utilization (rCMRglc) in four patients with fatal familial insomnia (FFI), a prion disease with a mutation at codon 178 of the prion protein gene. Two patients, presenting only with insomnia and dysautonomia, had a prominent and, in one case, selective thalamic hypometabolism. The remaining two cases presented a more complex clinical picture with multiple neurologic deficits, with both thalamic and widespread brain hypometabolism involving the majority of cortical structures, basal ganglia, and the cerebellum. This widespread pattern was present in the early stage of the disease and showed significant worsening as the disease progressed in one patient examined twice. The thalamic hypometabolism, consistently found with PET in FFI patients, is in agreement with the neuropathologic findings and is a hallmark of the disease.

Senile plaques in cerebral amyloid angiopathy show accumulation of amyloid precursor protein without cytoskeletal abnormalities

The abnormal neurites that surround beta-amyloid in senile plaques (SP) in Alzheimer disease contain beta-amyloid precursor protein (beta APP) or abnormal filaments which react with antibodies to tau. Occasionally, beta APP and abnormal filaments are present in the same neurite. Whether both types of abnormal neurites are reactive to the presence of beta-amyloid or they are instead independent from each other is unknown. To begin to clarify this issue, we comparatively studied beta APP and tau-epitopes in SP from cases of classical Alzheimer disease and cases of cerebral amyloid angiopathy, with SP but without neurofibrillary pathology. In subjects with cerebral amyloid angiopathy, about one-third of SP, the same percentage as in Alzheimer disease, were beta APP reactive in the absence of tau-reactivity. beta APP epitopes were ultrastructurally localized in dense bodies of probable lysosomal origin, adjacent to the core of SP. These results demonstrate that beta APP and tau-reactive cytoskeletal alterations occur independently in the neurites of SP. The presence of beta APP in dystrophic neurites of SP and the localization of beta APP in lysosomes suggest that beta APP containing dystrophic neurites may play a role in the extracellular deposition of amyloid.

Amyloidoma of the CNS. I. Clinical and pathologic study

We report a 32-year-old man with a 4-year history of headaches, seizures, and dementia secondary to multifocal amyloidomas in the white matter. Immunohistochemical and electron microscopic analyses suggest that the amyloidomas resulted from processing of plasma-cell-derived amyloidogenic protein by microglial cells.

"Fatal familial insomnia": neuropsychological study of a disease with thalamic degeneration

Fatal Familial Insomnia (FFI) is an inherited disease characterized clinically by sleep, autonomic and motor disturbances and pathologically by marked atrophy of the anterior and dorsomedial nuclei of the thalamus. The neuropsychological study of three cases of FFI showed: (1) a progressive disturbance of attention and vigilance, (2) a memory deficit with lability of mnesic traces and difficulty in manipulation and ordering of events, suggesting an alteration of working memory and (3) a deficit of frontal abilities with impairment in planning and prevision of events but preservation of general intelligence.

Abnormal sympathetic skin responses in thalamic lesions

Sympathetic skin responses (SSRs) were abolished in 4 patients affected with fatal familial thalamic degeneration involving the anterior (A) and dorsomedial (DM) thalamic nuclei, without lesions of the peripheral vegetative system. Abnormalities of SSR were not due to peripheral nerve lesions. It is concluded that SSR integrity also depends upon thalamic formations ("visceral" thalamus) and their frontal cortical connections.

Role of amyloid precursor protein (APP): study with antisense transfection of human neuroblastoma cells

The function of amyloid precursor protein (APP) was investigated in human neuroblastoma La-N-1 cells by stable transfection with a DNA construct encoding antisense APP mRNA. Levels of APP mRNA, as well as proteins, were reduced by 80-90% in antisense APP transfected (ASAT) cells. ASAT cells exhibited three main features as a result of APP gene expression deprivation: (1) a 30% reduction in cell proliferation, (2) reduced cell adhesion that could be reversed by the addition of La-N-1 conditioned media as a source of secreted APP, and (3) a two- and four-fold increase in neurite-bearing cells suggesting that cellular APP may be involved in neurite extension. The first two features confirm previously reported functions for APP in proliferation and adhesion of non-neuronal cell types but the use of neuroblastoma cells in this study disclose a novel role for cellular APP in neurite extension.

Subcellular localization of amyloid precursor protein in senile plaques of Alzheimer's disease

The authors have previously shown that amyloid precursor protein (APP) accumulates in neurites present in senile plaques of Alzheimer's disease (AD). In this ultrastructural immunocytochemical study, we describe the subcellular site of APP accumulation. Vibratome sections of glutaraldehyde-paraformaldehyde fixed hippocampi from five cases of AD were pretreated with methanol and immunostained with an antibody raised against recombinant APP 770 by using either indirect immunogold or peroxidase methods. Immunolabeling was localized in cell processes filled with amorphous, irregular-shaped materials, which were identified as dense bodies deformed by postmortem autolysis and methanol treatment, as well as multilamellar membranous bodies. Identification of these bodies was obtained with comparative ultrastructural examination of biopsy and autopsy tissue fixed with and without methanol treatment. These electron-dense organellae were positive for the lysosomal marker, acid phosphatase. At light microscopy, acid phosphatase and APP colocalized to the same cell processes in senile plaques. Many of those cell processes contained abnormal straight or paired helical filaments supporting their neuritic nature. These results suggest that APP accumulates in the lysosomal system of the dystrophic neurites present in senile plaques and are consistent with a neuronal origin of the APP forming the amyloid in senile plaques.

Production of single-stranded DNA for sequencing: an alternative approach

We describe a simple procedure for the direct sequencing of single-stranded, PCR-amplified, target regions of human genomic DNA. At variance with previously reported procedures, purification of the desired double-stranded DNA was introduced. This additional step allowed the single-stranded amplification and sequencing of the target gene. This step is required for direct sequencing of some amplified regions of human genomic DNA. However, no individual technique seems suitable to generate and sequence all single-stranded DNA.

Fatal familial insomnia

Fatal familial insomnia (FFI), a condition characterized by inability to sleep, dysautonomia, motor disturbances, and selective thalamic atrophy is a prion disease linked to a GAC→C mutation at codon 178 of the prion gene. These data were obtained from one kindred. We now report a second kindred affected by FFI and carrying the same mutation. The finding of the same disease phenotype and genotype in a second family further validates FFI as a distinct disease entity and a phenotype of the GAC→C mutation at codon 178 of the prion gene.

Differential APP gene expression in rat cerebral cortex, meninges, and primary astroglial, microglial and neuronal cultures

Differential amyloid precursor protein (APP) gene expression was investigated in primary cultures of astrocytes, neurons and microglia from neonatal rat cerebral cortex as well as in meninges, and young and adult cerebral cortex tissues in order to define the possible contribution of individual CNS cell types in beta AP deposition. Meninges and neurons contained higher levels of total APP mRNA than glial cells and APP695 mRNA was abundant in neurons while glial cells and meninges contained higher levels of KPI-containing mRNAs. These results demonstrate cell-specific transcriptional and post-transcriptional regulation of APP gene expression in CNS cell types. In addition, the steady-state level of APPs in each cell type did not reflect mRNA levels indicating translational or post-translational regulation.

Amyloid precursor protein and ubiquitin immunoreactivity in dystrophic axons is not unique to Alzheimer's disease

A distinctive feature of Alzheimer's disease (AD) is the presence of dystrophic neurites that immunoreact with antibodies to amyloid precursor protein (APP) and ubiquitin (Ub). The authors examined dystrophic axons (DA) present in other chronic conditions such as familial infantile neuroaxonal dystrophy (INAD), aging, cystic fibrosis, and biliary obstruction as well as in conditions of shorter duration such as human immunodeficiency virus (HIV) leucoencephalopathy, infarction and radiation therapy to determine whether APP and Ub immunoreactivity was unique to the DA of AD. A large number of DA immunoreacted with antibodies to the A4, C- and N-terminal regions of APP as well as to Ub. Ub and APP immunoreactivities often, but not always, colocalized. "Acute" DA generally reacted more intensely and in larger number with antibodies to APP than to Ub, whereas the reverse was true for "chronic" DA. Structureless DA immunostained diffusely. In DA with cores or granules, the Ub immunoreaction was occasionally limited to these structures, whereas reaction with antibodies to APP was more diffuse. In view of the contention that impairment of proteolysis is the common pathogenetic step in the formation of DA, Ub immunoreactivity in all DA may indicate a vicarious attempt to degrade accumulated components through an activation of the Ub system. The role of APP in the formation of DA remains to be determined.

Ubiquitin in motor neuron disease: study at the light and electron microscope

Several neurodegenerative diseases, including motor neuron disease (MND), are characterized by formation of abnormal cytoskeleton-derived inclusions which contain ubiquitin (Ubq). We have studied the distribution of Ubq in 26 cases of MND with light and electron microscopic immunocytochemistry. Ubiquitin-positive inclusions were found in neurons of anterior horns in most cases of amyotrophic lateral sclerosis (ALS) but were not present in other forms of MND. Ubiquitin immunoreactivity was observed in 10-15 nm intraneuronal filaments, which were not stained by antibodies to neurofilaments, and on dense bodies of dystrophic neurites throughout the neuropil of anterior horns and pyramidal tracts. Data analysis showed a trend toward lower percentage of Ubq-positive neurons in cases with longer duration of illness or lower number of neurons. A high percentage of Ubq-positive inclusions occurred in cases with an aggressive clinical course, suggesting that ubiquitination takes place at early stages of the disease.