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L Autilio-Gambetti

Publications and source records attributed to L Autilio-Gambetti.

10 recordsLinked to original sources
PubMed1992

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.

Amyloid beta-Protein Precursor↗
PubMed1991

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 beta-Protein Precursor↗
PubMed1991

Axonal transport of two major components of the ubiquitin system: free ubiquitin and ubiquitin carboxyl-terminal hydrolase PGP 9.5.

Ubiquitin (Ub), a stress protein thought to target abnormal proteins for degradation, is present in abnormal structures that occur in neuronal perikarya and axons of degenerative diseases including Alzheimer disease. To begin to assess the role of the Ub system in the axon, we studied expression and axonal transport of Ub and other stress proteins, as well as of Ub carboxyl-terminal hydrolase PGP 9.5, in the rat visual system in normal conditions and following heat-shock (HS). In the retina, both the constitutive and inducible forms of HSPs 70 were expressed under normal conditions, while in the superior colliculus the inducible form was detected only following HS. Ub, PGP 9.5 and HSPs 70 were transported in the axon exclusively with the slow component b (SCb), known to carry cytoskeletal and cytoplasmic proteins. The exceedingly long time needed for stress proteins to reach distant axonal locales at the rate of SCb (approximately 3 mm/day) makes it unlikely that they could contribute significantly to the stress response at those sites.

Animals↗
PubMed1991

Ultrastructural localization of beta-amyloid, tau, and ubiquitin epitopes in extracellular neurofibrillary tangles.

Neurofibrillary tangles (NFTs), a hallmark of Alzheimer disease, are commonly located in perikarya of neurons. In advanced cases of Alzheimer disease, however, NFTs are observed also in the extracellular space. As extracellular NFTs (E-NFTs), and occasionally intracellular NFTs (I-NFTs), are recognized by antibodies to beta-amyloid protein (beta AP), beta AP may be present not only in amyloid deposits but also in paired helical filaments (PHFs), the primary components of NFTs. We compared the antigenic characteristics of I-NFTs and E-NFTs with light- and electron-microscopic immunocytochemistry by using several antibodies to noncontiguous epitopes of the microtubule-associated protein tau and of ubiquitin (Ub) as well as an antiserum to beta AP. At variance with I-NFTs, E-NFTs were made predominantly of straight filaments (SFs), rather than PHFs, that were often separated by astroglial processes and in close association with small beta AP deposits. Occasionally, E-NFTs were made of bundles of amorphous material, which showed no resemblance to SFs, PHFs, or amyloid fibrils. The antigenic changes in E-NFTs suggest that when NFTs become extracellular they lose the N and, possibly, the C termini of tau while maintaining the intermediate region of the molecule; they also lose the N-terminal two-thirds of Ub while the C-terminal conjugation site of Ub is preserved. A small subset of E-NFTs reacted with antibodies to both beta AP and tau. Although in most E-NFTs, the epitopes recognized by tau and Ub antibodies were located in typical PHFs and SFs, the epitopes recognized in this subset of anti-beta AP and anti-tau-positive E-NFTs were located exclusively in the bundles of amorphous material. It is suggested that either beta AP epitopes are present but inaccessible in PHFs and SFs and become exposed after conformational changes occurring in the extracellular space or PHFs and SFs become closely associated with beta AP in the extracellular space.

Alzheimer Disease↗
PubMed1991

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.

Adult↗
PubMed1991

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.

Adolescent↗
PubMed1990

Role of cytokeratin intermediate filaments in transhepatic transport and canalicular secretion.

The role of cytokeratin filaments in the function of hepatocytes was investigated using a nickel-treated hepatocyte in vitro model. Cytokeratin intermediate filaments were selectively dissociated from the cell cortex by nickel treatment. Cytokeratins and ubiquitin were observed using immunofluorescence and immunoelectron microscopy. Hepatocytic function was assessed by visualizing uptake, transhepatic transport and secretion of fluorescein diacetate and horseradish peroxidase into the bile canaliculi. In control primary cultures, most of the bile canaliculi were surrounded by an inner layer of actin filaments and an outer pericanalicular sheath of cytokeratin filaments and microtubules. The cytoplasmic distribution of ubiquitin was diffuse and particulate. After treatment with NiCl2 (150 micrograms/ml) for 24 hr, the cytokeratin filaments and desmoplakin became focally detached from the cell cortex and retracted to form an aggregate around the nucleus. These aggregates were associated with intense ubiquitin immunoreactivity. Only a few attachments of the cytokeratin filaments to the cell cortex remained. F-actin remained attached to the cell cortex in the areas where the cytokeratin filaments had become detached. The pericanalicular sheath of cytokeratin filaments and the bile canaliculi disappeared and actin was dispersed over the entire cell periphery. Fluorescein diacetate secretion and horseradish peroxidase uptake were almost completely absent in the hepatocytes treated with nickel. The effects of nickel persisted 24 hr after its removal from the medium. It is concluded that cytokeratin intermediate filaments play a critical role in the formation of the bile canaliculus, secretion of fluorescein diacetate and uptake of horseradish peroxidase. Further, our study indicates that cytokeratin ubiquitination occurs during collapse and aggregation of the cytokeratin filaments. The formation of cytokeratin-ubiquitin conjugates during aggregation suggests a role of ubiquitin in the control of cytokeratin organization in hepatocytes in the response to cell stress.

Animals↗