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B De Strooper

Publications and source records attributed to B De Strooper.

63 records · Page 4Linked to original sources
PubMed1992

Alpha 2-macroglobulin and other proteinase inhibitors do not interfere with the secretion of amyloid precursor protein in mouse neuroblastoma cells.

A series of proteinase inhibitors active against proteinases of all four major classes, including highly purified and well-characterized alpha 2-macroglobulin, added to the cell culture medium of murine Neuro 2a neuroblastoma cells did not interfere with APP secretase activity. We therefore advance the hypothesis that APP secretase activity is localized in an intracellular compartment.

Amyloid beta-Protein Precursor↗
PubMed1991

The amyloid beta protein precursor or proteinase nexin II from mouse is closer related to its human homolog than previously reported.

The cDNA sequence for amyloid precursor protein and the two alternatively spliced forms were determined. Seven nucleotide differences resulting in six amino acid differences compared to the previously published mouse sequence were found. Moreover, the 3' non-coding end was completely different. Part of these findings were confirmed in three different mouse strains. The resulting mouse cDNA resembles the human APP more closely than originally reported.

Amino Acid Sequence↗
PubMed1991

Cultured human fibroblasts contain a large pool of precursor beta 1-integrin but lack an intracellular pool of mature subunit.

Previous work has shown the presence of an important intracellular pool of beta 1-integrin subunit in human skin fibroblasts as detected with monoclonal antibody DH12 [De Strooper, B., Van der Schueren, B., Jaspers, M., Saison, M., Spaepen, M., Van Leuven, F., Van den Berghe, H. & Cassiman, J. J. (1989) J. Histochem. Cytochem. 37,299-307]. To analyze this more quantitatively, a radioimmunoassay with radioiodinated monoclonal antibody was developed. The total amount of specific binding sites for monoclonal antibody DH12 on skin fibroblasts was between 0.8-1.5 x 10(6)/cell. After permeabilizing the cells with digitonin, a threefold increase in specific binding was observed, which suggested that about 60% of the total amount of beta 1-subunit was localized intracellularly. From pulse/chase experiments, it was deduced that an important pool of precursor subunit, as defined by its sensitivity to endoglycosidase treatment, existed in fibroblasts. Since in steady-state-labeling conditions, at least three to four times more precursor than mature subunit was immunoprecipitated with monoclonal antibody DH12, we suggested that the intracellular pool of beta 1-integrin subunit is mainly precursor pool. This precursor pool contains a degradation compartment and a maturation compartment. Other investigators have found evidence for a recirculating pool of mature integrin in Chinese hamster ovary cells. Therefore, the presence of a recirculating pool of integrin in human fibroblasts was also considered. The data obtained with mAb DH12 showed that less than 10% of the surface pool of integrin was internalized by endocytosis. Since, however, cross linking of beta 1-integrins with polyclonal antibodies leads to rapid endocytosis of most of the integrin, it remains possible that the quantitatively small effect was actually an artefact induced by the divalent mAb. We conclude that the intracellular pool of beta 1-integrins observed in our previous studies consists of precursor and that in skin fibroblasts no mature beta 1-integrin is available intracellularly for rapid quantitative modulations at the cell surface.

Acetylglucosaminidase↗
PubMed1989

Distribution of the beta 1 subgroup of the integrins in human cells and tissues.

We studied the distribution of the beta 1 integrin subfamily in human tissues and cells by light microscopy, electron microscopy, and immunoblotting, using monoclonal antibody DH12, previously shown to react with the beta 1 subunit of the human fibronectin receptor. Crossreaction with the other beta subunits of the integrin family, which have 45% and 47% primary amino acid sequence identity with the beta 1 subunit, was excluded, as MAb DH12 did not react with the beta 2 subunit in granulocytes and the beta 3 subunit in thrombocytes. Reactivity with the anti-beta 1 antibody was found in skin, lung, heart, striated and smooth muscle, blood cells, liver, kidney, intestine, spleen and placenta. Thus, cells of mesodermal, ectodermal, and entodermal origin express the beta 1 subunit. In skin fibroblasts cultured in vitro, beta 1 subunit was also detected intracellularly. The wide distribution of the beta 1 family, originally detected in activated T-lymphocytes after prolonged culture in vitro, contrast with the restricted distribution of the beta 2 integrins on leucocytes.

Antibodies, Monoclonal↗
PubMed1988

Mapping of human fibronectin receptor beta subunit gene to chromosome 10.

Human-mouse hybrid cells were examined by indirect immunofluorescence with Mab DH12, a monoclonal antibody that recognizes the beta subunit of the human fibronectin receptor. Cells that expressed the antigen at their surface were sorted by FACS and karyotyped. Immunoaffinity chromatography on Mab DH12 was used to confirm the presence of the human antigen. The chromosome assignment was strengthened by isozyme analysis of markers for chromosomes 9 and 10. The results are suggestive for a 10p mapping of this beta subunit of the fibronectin receptor. Since the gene coding for the beta subunit of the VLA proteins was previously assigned to the same chromosome, our result could provide further evidence for the relationship between the beta subunit of the human fibronectin receptor and the VLA protein family.

Animals↗
PubMed1988

Monoclonal antibody DH12 reacts with a cell surface and a precursor form of the beta subunit of the human fibronectin receptor.

Monoclonal and polyclonal antibodies were raised against a placenta plasma membrane protein preparation, which was obtained by fractionation on Blue B dye matrix and by HPLC-anionexchange, and which was shown to contain fibronectin receptors. Immunochemical and functional evidence showed that monoclonal antibody DH12 recognized the beta subunit of the human fibronectin receptor on fibroblasts. This monoclonal antibody reacted with two proteins in Western blots and in double immune precipitations of whole cell preparations. Only the higher Mr protein became labeled by surface iodination of intact fibroblasts. The lower Mr protein is thought to be an intracellular precursor of the beta subunit of the fibronectin receptor.

Animals↗
PubMedDate not supplied

alpha 2-Macroglobulin expression in neuritic-type plaques in patients with Alzheimer's disease.

Because it has been suggested that alpha 2M could be involved in the generation of amyloid peptide, attention was given to a possible association of alpha 2M expression and amyloid accumulation in the brain. Therefore, we investigated the presence of the proteinase inhibitor alpha 2-macroglobulin (alpha 2M) in the cerebra of 4 patients with Alzheimer's Disease (AD). One case of a patient with Down's syndrome, 2 cases of patients with Dementia of the Lewy Body type (DLB), 1 case of an aged, clinically nondemented person who displayed many amyloid plaques, and 3 normal aged control brains were also studied. The results obtained by immunocytochemistry with monoclonal antibodies directed against two different epitopes of human alpha 2M showed an association of alpha 2M, only with neuritic-type plaques in patients with AD. No alpha 2M immunoreactivity was found in either preamyloid-type plaques or burned out-type plaques in AD, DLB, or aged nondemented controls. The results do not support a direct role of this proteinase inhibitor in the formation of amyloid. Because alpha 2M is observed to be associated with reactive microglia in the outer border of the neuritic plaques, the data suggest that alpha 2M could be a marker for an inflammatory cellular process in these neuritic plaques.

Aged↗
PubMedDate not supplied

Amyloid precursor protein accumulation in Lewy body dementia and Alzheimer's disease.

The presence of amyloid precursor protein (APP) and beta-amyloid protein (beta A4) was investigated in the cerebra of 4 patients with Alzheimer's disease (AD), 1 patient with Down's syndrome, 4 patients with dementia of the Lewy body type (DLB) and 4 age-matched, clinically nondemented controls, of which one displayed many amyloid plaques. The different types of amyloid plaques stained strongly with antibodies against beta A4. Antibodies against the C-terminal region of APP reacted only weakly with small swollen neurites and with globular deposits in neuritic-type plaques from patients with AD. The antibody against the N-terminal region of APP stained strongly cellular elements in the neuritic type plaques of patients with AD but not dense cored plaques. In contrast, patients with DLB displayed with this antibody a homogeneous staining of dense cored amyloid plaques. Some Lewy bodies stained with the antibody against the N-terminal region of APP as well. These results indicate that the processing of APP in AD and DLB could be different, to yield different fragments deposited in AD and DLB amyloid plaques.

Aged↗