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W J Strittmatter

Publications and source records attributed to W J Strittmatter.

At least 73 records · Page 4Linked to original sources
PubMed1993

Apolipoprotein E: high-avidity binding to beta-amyloid and increased frequency of type 4 allele in late-onset familial Alzheimer disease.

Apolipoprotein E is immunochemically localized to the senile plaques, vascular amyloid, and neurofibrillary tangles of Alzheimer disease. In vitro, apolipoprotein E in cerebrospinal fluid binds to synthetic beta A4 peptide (the primary constituent of the senile plaque) with high avidity. Amino acids 12-28 of the beta A4 peptide are required. The gene for apolipoprotein E is located on chromosome 19q13.2, within the region previously associated with linkage of late-onset familial Alzheimer disease. Analysis of apolipoprotein E alleles in Alzheimer disease and controls demonstrated that there was a highly significant association of apolipoprotein E type 4 allele (APOE-epsilon 4) and late-onset familial Alzheimer disease. The allele frequency of the APOE-epsilon 4 in 30 random affected patients, each from a different Alzheimer disease family, was 0.50 +/- 0.06; the allele frequency of APOE-epsilon 4 in 91 age-matched unrelated controls was 0.16 +/- 0.03 (Z = 2.44, P = 0.014). A functional role of the apolipoprotein E-E4 isoform in the pathogenesis of late-onset familial Alzheimer disease is suggested.

Alleles↗
PubMed1993

Avid binding of beta A amyloid peptide to its own precursor.

The senile plaque and congophilic angiopathy in brains of patients with Alzheimer's disease contain abnormal extracellular depositions. These depositions have very complex molecular structure, some elements of which have been identified. The most abundant protein in these structures is beta A amyloid peptide, which is produced by proteolytic processing of a larger protein, the amyloid precursor protein. It is not known how plaques and angiopathy are formed. Binding of proteins with the beta A peptide may be critical in this process. Using synthetic beta A peptides we show that the amyloid precursor protein found in cerebrospinal fluid binds beta A peptide with high avidity. Analysis of recombinant amyloid precursor proteins containing deletions of various domains demonstrate that the beta A peptide binds to the amino terminus of its own precursor. A model of plaque assembly is presented.

Amino Acid Sequence↗
PubMed1993

Association of apolipoprotein E allele epsilon 4 with late-onset familial and sporadic Alzheimer's disease.

Apolipoprotein E, type epsilon 4 allele (APOE epsilon 4), is associated with late-onset familial Alzheimer's disease (AD). There is high avidity and specific binding of amyloid beta-peptide with the protein ApoE. To test the hypothesis that late-onset familial AD may represent the clustering of sporadic AD in families large enough to be studied, we extended the analyses of APOE alleles to several series of sporadic AD patients. APOE epsilon 4 is significantly associated with a series of probable sporadic AD patients (0.36 +/- 0.042, AD, versus 0.16 +/- 0.027, controls [allele frequency estimate +/- standard error], p = 0.00031). Spouse controls did not differ from CEPH grandparent controls from the Centre d'Etude du Polymorphisme Humain (CEPH) or from literature controls. A large combined series of autopsy-documented sporadic AD patients also demonstrated highly significant association with the APOE epsilon 4 allele (0.40 +/- 0.026, p < or = 0.00001). These data support the involvement of ApoE epsilon 4 in the pathogenesis of late-onset familial and sporadic AD. ApoE isoforms may play an important role in the metabolism of beta-peptide, and APOE epsilon 4 may operate as a susceptibility gene (risk factor) for the clinical expression of AD.

Aged↗
PubMed1992

Identification of human T cells that require zinc for growth.

Zinc is an essential trace element required for normal function of the immune system. Deficiency of zinc results in marked thymic atrophy in experimental animals, and in man immunodeficiency is a recognized complication of zinc deprivation. Although numerous proteins require zinc as a cofactor, its precise functions in the immune system remain unknown. The mechanism by which metals stimulate lymphocytes, whether all T cells are responsive, and the relationship to zinc requirements have not been determined. We unexpectedly isolated a number of human T-cell lines that have a highly specific requirement for zinc. The ability to respond to zinc resides in only a subset of T cells since antigen-specific clones are not stimulated by zinc. Although proliferation requires the presence of antigen-presenting cells and is restricted by class II MHC antigens, antigen-presenting cells could not be pulsed with zinc to induce T-cell activation. Our results suggest that zinc-dependent T cells are a subset of CD4+ cells present in all normal individuals and that zinc stimulates their growth by novel mechanisms.

Antigen-Presenting Cells↗
PubMed1990

Low yield in the diagnostic evaluation of transient ischemic attacks.

Among 163 patients presenting with the clinical features of a TIA, extensive testing identified only 2 patients with nonatherosclerotic causes. We conclude that most patients with a TIA have atherosclerotic vascular disease and that screening tests for other etiologies have a low yield.

Algorithms↗
PubMed1989

Inhibitors of metalloendoproteases block spiculogenesis in sea urchin primary mesenchyme cells.

Metalloendoproteases have been implicated in a variety of fusion processes including plasma membrane fusion and exocytosis. As a prerequisite to skeleton formation in the sea urchin embryo, primary mesenchyme cells undergo fusion via filopodia to form syncytia. The spicule is formed within the syncytial cable by matrix and mineral deposition. To investigate the potential involvement of a metalloendoprotease in spiculogenesis, the effect of inhibitors of this enzyme on skeleton formation was studied. Experiments with primary mesenchyme cells in vitro and in normal embryos revealed that skeleton formation was blocked by these inhibitors. These findings implicate a metalloendoprotease in spiculogenesis; such an enzyme has been demonstrated in homogenates of primary mesenchyme cells. The most likely site of action of the metalloendoprotease is at the cell membrane fusion stage and/or at subsequent events requiring membrane fusion.

Animals↗
PubMed1988

Molecular mechanisms of exocytosis: the adrenal chromaffin cell as a model system.

1. The release of neurotransmitters, hormones, and enzymes involves exquisitely regulated events which ultimately result in the fusion of the secretory vesicle with the cell's plasma membrane, releasing the vesicle contents into the extracellular space. 2. The biochemical and cellular mechanisms mediating exocytosis have been extensively studied in a model system of primary cultured adrenal chromaffin cells. 3. This paper briefly reviews current understanding, and directions of future studies in exocytosis using this model system.

Adrenal Medulla↗
PubMed1988

Glutamate and dynorphin release from a subcellular fraction enriched in hippocampal mossy fiber synaptosomes.

A procedure is described for the isolation of intact hippocampal mossy fiber synaptosomes. Electron microscopic examination revealed numerous synaptosomal profiles which are clearly of mossy fiber origin, indicated by their large size (2-6 micron diameter) and characteristic morphology. Furthermore, this fraction is enriched in zinc and dynorphin B which appear to be concentrated in mossy fiber terminals in vivo. Synaptosomes isolated by this procedure accumulated 2-deoxyglucose and retained 88% of total lactate dehydrogenase activity after incubation at 30 degrees C for 60 minutes, indicating a high degree of membrane integrity. Oxygen consumption was stimulated 4-fold by veratridine (0.1 mM) and inhibited 90% by ouabain (1 mM), suggesting that synaptosomal metabolism remained tightly coupled to ouabain-sensitive ATPase activity. Potassium-stimulated (45 mM) release of dynorphin B was completely dependent upon the presence of extrasynaptosomal calcium, while only 30% of the evoked release of glutamate was calcium-dependent. D-aspartate, which exchanges glutamate out of the cytoplasmic pool, virtually eliminated the calcium-independent component of glutamate release. This synaptosomal preparation will be useful in identifying the factors that modulate the release of amino acid and opioid neurotransmitters from hippocampal nerve terminals and in the investigation of their presynaptic mechanisms of action.

Animals↗
PubMed1988

Evidence for involvement of metalloendoproteases in a step in sea urchin gamete fusion.

Membrane fusion events are required in three steps in sea urchin fertilization: the acrosome reaction in sperm, fusion of the plasma membrane of acrosome-reacted sperm with the plasma membrane of the egg, and exocytosis of the contents of the egg cortical granules. We recently reported the involvement of a Zn2+-dependent metalloendoprotease in the acrosome reaction (Farach, H. C., D. I. Mundy, W. J. Strittmatter, and W. J. Lennarz. 1987. J. Biol. Chem. 262:5483-5487). In the current study, we investigated the possible involvement of metalloendoproteases in the two other fusion events of fertilization. The use of inhibitors of metalloendoproteases provided evidence that at least one of the fusion events subsequent to the acrosome reaction requires such enzymes. These inhibitors did not block the binding of sperm to egg or the process of cortical granule exocytosis. However, sperm-egg fusion, assayed by the ability of the bound sperm to establish cytoplasmic continuity with the egg, was inhibited by metalloendoprotease substrate. Thus, in addition to the acrosome reaction, an event in the gamete fusion process requires a metalloendoprotease.

Acrosome↗
PubMed1987

The soluble metalloendoprotease required in myoblast fusion remains intracellular.

The fusion of myoblasts to myotubes requires an endogenous soluble metalloendoprotease. To determine whether this protease is released by fusing myoblasts, or stays within the cell, we examined the effects of membrane-impermeant and a membrane-permeant metalloendoprotease inhibitors. Membrane-permeant 1,10-phenanthroline, and membrane-impermeant bathophenanthroline disulfonic acid both inhibited soluble metalloendoprotease activity in homogenized myoblasts with equal potency. However, while 1,10-phenanthroline inhibited fusion, bathophenanthroline disulfonic acid had no effect. In addition, metalloendoprotease activity could not be detected in the media of fusing myoblasts, but was in the cells. These observations support the conclusion that the soluble metalloendoprotease required in fusion remains within the myoblast.

Animals↗
PubMed1987

Evidence for the involvement of metalloendoproteases in the acrosome reaction in sea urchin sperm.

An essential initial step in fertilization in the sea urchin Strongylocentrotus purpuratus is an intracellular membrane fusion event in the sperm known as the acrosome reaction. This Ca2+-dependent, exocytotic process involves fusion of the membrane of the acrosomal vesicle and the plasma membrane. Recently, metalloendoproteases requiring divalent metals have been implicated in several Ca2+-dependent membrane fusion events in other biological systems. In view of the suggested involvement of Zn2+ in the sea urchin sperm acrosome reaction (Clapper, D.L., Davis, J.A., Lamothe, P.J., Patton, C., and Epel, D. (1985) J. Cell Biol. 100, 1817-1824) and the fact that Zn2+ is a metal cofactor for metalloendoproteases, we investigated the potential role of this protease in the acrosome reaction. A soluble metalloendoprotease was demonstrated and characterized in sperm homogenates using the fluorogenic protease substrate succinyl-alanine-alanine-phenylalanine-4-aminomethylcoumarin. The protease was inhibited by the metal chelators EDTA and 1,10-phenanthroline, and activity of the inactive apoenzyme could be reconstituted with Zn2+. The metalloendoprotease substrate and inhibitors blocked the acrosome reaction induced either by egg jelly coat or by ionophore, but had no effect on the influx of Ca2+. These observations suggest that inhibition occurs at a step independent of Ca2+ entry. Overall, the results of this study provide strong indirect evidence that the acrosome reaction requires the action of metalloendoprotease.

Acrosome↗
PubMed1987

Specific inhibitors implicate a soluble metalloendoproteinase in exocytosis.

1. Previous studies have demonstrated that exocytosis in adrenal chromaffin cells appears to require zinc-dependent endoproteinase activity. 2. Chromaffin cells have metal-dependent endoproteinases in both the plasma membrane and the soluble fraction of homogenized cells. In order to further study critically the role of metalloproteinase in exocytosis, and prior to purification, we needed to determine which one of several adrenal metalloproteinases is implicated in exocytosis. 3. The studies described here demonstrate that the metal-dependent endoproteinases in these two subcellular fractions can be differentiated by selective inhibitors. In both intact and permeabilized cells, the plasma membrane metalloproteinase, but not the soluble proteinases, is inhibited by phosphoramidon. Phosphoramidon does not block exocytosis in either intact or permeabilized cells. 4. In addition, the plasma membrane metalloproteinase appears to have its catalytic site facing the outside of the cell. 5. Because of these observations the plasma membrane metalloproteinase does not appear to be required in exocytosis. Since soluble metalloproteinase activity is inhibited by proteinase inhibitors at concentrations which block exocytosis, a soluble, and not the plasma membrane, metalloproteinase appears to be required in exocytosis.

Acetophenones↗
PubMed1985

Requirement for metalloendoprotease in exocytosis: evidence in mast cells and adrenal chromaffin cells.

Exocytosis is initiated by the receptor-mediated influx of calcium that results in fusion of the secretory vesicle with the plasma membrane. We examined the possibility that calcium-dependent exocytosis in mast cells and adrenal chromaffin cells requires metalloendoprotease activity. Metalloendoprotease inhibitors and dipeptide substrates block exocytosis in these cells with the same specificity and dose dependency as that with which they interact with metalloendoproteases. Metalloendoprotease activity is identified in these cells with fluorogenic synthetic substrates, which also blocked exocytosis. Metalloendoprotease activity is highest in the plasma membrane of chromaffin cells. The metalloendoprotease appears to be required in exocytosis at a step dependent on or after calcium entry, since exocytosis initiated by direct calcium introduction in both mast cells and chromaffin cells is blocked by metalloendoprotease inhibitors.

Adrenal Glands↗
PubMed1984

Specific blockers of myoblast fusion inhibit a soluble and not the membrane-associated metalloendoprotease in myoblasts.

We previously reported that the cell fusion that occurs during muscle development, when mononucleated myoblasts fuse to form multinucleated myotubes, requires endogenous metalloendoprotease activity at the time of fusion. We report here that myoblasts contain both soluble and membrane-associated metalloendoproteases, and that these proteases have different inhibitor specificities. Several inhibitors, previously shown to block myoblast fusion, inhibit only soluble and not membrane-associated metalloendoprotease activity in myoblasts. Another metalloendoprotease inhibitor, phosphoramidon, which had no effect on fusion, inhibits only the membrane-associated metalloendoprotease. These observations implicate a soluble metalloendoprotease in myoblast fusion. Two soluble metalloendoproteases can be demonstrated by column chromatofocusing, with pI values at pH 5.9 and 4.8. The soluble metalloendoprotease eluted at pH 5.9 is not inhibited by an inhibitor which blocks fusion, while the soluble metalloendoprotease eluted at pH 4.8 is inhibited. Of the three metalloendoprotease activities identified in myoblasts, the metalloendoprotease required in myoblast fusion appears to be the soluble metalloendoprotease with a pI of 4.8.

Animals↗
PubMed1984

Inhibitors of metalloendoprotease activity prevent K+-stimulated neurotransmitter release from the retina of Xenopus laevis.

Metalloendoprotease activity was identified in retinal homogenates using a synthetic fluorogenic metalloendoprotease substrate and specific metalloendoprotease inhibitors. The requirement of metalloendoprotease activity in neurotransmitter release was examined during the depolarization-induced release of [3H]glycine from the retina of Xenopus laevis. Neurons with high affinity uptake and calcium-dependent, K+-stimulated release of glycine have been described previously in this retina. When isolated retinas preloaded with [3H]glycine are depolarized by 22 mM K+, the usual efflux of [3H]glycine is completely abolished by the metalloendoprotease inhibitor, 1,10-phenanthroline (100 micrograms/ml). The inhibition of [3H]glycine release by 1,10-phenanthroline is dose dependent; furthermore, 1,10-phenanthroline blocks release by chelating metal and not Ca2+, since addition of equimolar calcium does not alter the inhibition. The metalloendoprotease inhibitor, carbobenzoxy (CBZ)-L-phenylalanine, also prevents release, whereas the amino acid, L-phenylalanine, has no effect. Synthetic carbobenzoxy dipeptide amides which are metalloendoprotease substrates (e.g., CBZ-Gly-Leu-amide, CBZ-Ser-Leu-amide, and CBZ-Gly-Phe-amide) also prevent [3H]glycine release in a dose-dependent and reversible manner. The synthetic dipeptide CBZ-Gly-Gly-amide, however, is not a metalloendoprotease substrate and has no effect on release. The ability of synthetic dipeptides to inhibit neurotransmitter release is amino acid specific, dose dependent, reversible, and matches their ability to interact with characterized metalloendoproteases. Depolarization-stimulated transmitter release may therefore require the activity of a metalloendoprotease.

Animals↗
PubMed1983

Rat myoblast fusion requires metalloendoprotease activity.

The calcium-dependent fusion of cultured rat myoblasts to multinucleate myotubes appears to require the activity of a neutral metalloendoprotease at the time of fusion. Metalloendoprotease inhibitors and synthetic dipeptide substrates prevent myoblast fusion when added to fusion-competent myoblasts with the addition of calcium. Metalloendoprotease activity has been identified and partially characterized in myoblast membranes with a fluorogenic protease substrate, and is inhibited by the same compounds that prevent fusion.

Animals↗