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  • 1
    Electronic Resource
    Electronic Resource
    Human Brain βA4 Amyloid Protein Precursor of Alzheimer's Disease: Purification and Partial Characterization (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 59 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The major component of the amyloid deposition that characterizes Alzheimer's disease is the 4-kDa βA4 protein, which is derived from a much larger amyloid protein precursor (APP). A procedure for the complete purification of APP from human brain is described. The same amino terminal sequence of APP was found in two patients with Alzheimer's disease and one control subject. Two major forms of APP were identified in human brain with apparent molecular masses of 100–110 kDa and 120–130 kDa. Soluble and membrane fractions of brain contained nearly equal amounts of APP in both humans and rats. Immunoprecipitation with carboxyl terminus-directed antibodies indicates that the soluble forms of APP are truncated. Carboxyl terminus truncation of membrane-associated forms of human brain APP was also found to occur during postmortem autolysis. The availability of purified human brain APP will facilitate the investigation of its normal function and the events that lead to its abnormal cleavage in patients with Alzheimer's disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb08465.x
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  • 2
    Electronic Resource
    Electronic Resource
    An Amyloid Peptide, βA4 25–35, Mimics the Function of Substance P on Modulation of Nicotine-Evoked Secretion and Desensitization in Cultured Bovine Adrenal Chromaffin Cells (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 60 (1993), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The amyloid protein (βA4) is found in the CNS of patients with Alzheimer's disease; however, the pathogenic role of this protein is not known. In the present study, a peptide fragment of βA4βA4 25–35; Gly-Ser-Asn-Lys-Gly-Ala-Ile-Ile-Gly-Leu-Met-NH2), which contains the conserved C-terminal sequence of substance P (X-Gly-Leu-Met-NH2), and the neuropeptide substance P (SP) were examined for their ability to modulate nicotine-evoked secretion from cultured bovine adrenal chromaffin cells. Secretion of the released endogenous catecholamines was monitored by electrochemical detection after separation by HPLC. Secretion induced by 10−5M nicotine was inhibited by SP and βA4 25–35. The IC50 of SP and βA4 25–35 was 3 × 10−6 and 3 × 10−5M, respectively. SP and βA4 25–35 both protected against nicotinic receptor desensitization. However, βA4 25–35 was ∼ 10-fold less effective than SP in its protective effect. The present work shows that βA4 25–35 can mimic the modulatory actions of SP on the nicotinic response of cultured bovine chromaffin cells, i.e., inhibition of the nicotinic response and protection against nicotinic desensitization. These modulatory actions may be associated with changes in nicotinic receptor levels reported to occur in Alzheimer's disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1993.tb03270.x
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  • 3
    Electronic Resource
    Electronic Resource
    A protease activity associated with acetylcholinesterase releases the membrane-bound form of the amyloid protein precursor of Alzheimer's disease (1991)
    s.l. : American Chemical Society
    Biochemistry 30 (1991), S. 10795-10799 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00108a027
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  • 4
    Electronic Resource
    Electronic Resource
    The Role of Extracellular Matrix in the Processing of the Amyloid Protein Precursor of Alzheimer's Disease (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 695 (1993), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: Alzheimer's disease (AD) is characterized by the presence of extracellular amyloid plaques, which contain a protein referred to as the amyloid or βA4 protein. The βA4 protein is derived from a larger precursor protein (APP). Studies of autosomal-dominant forms of AD have established the central role of APP in the pathogenesis of the disease. Despite considerable research, the function of APP is unknown. APP can be processed by at least two separate routes. The first route involves a protease known as “APP secretase,” which cleaves within the amyloid sequence, thereby mitigating amyloid formation. The second route may result in the production of potentially amyloidogenic fragments. Our studies suggest that following release from the cell membrane, APP interacts with components of the extracellular matrix (ECM) such as the heparan sulfate proteoglycans (HSPG's). The interaction of APP with HSPG's may be important for the function of APP. Substratum-bound APP was found to dramatically increase neurite outgrowth and survival of chick sympathetic neurons in vitro. This effect was dependent upon the presence of substratum-bound HSPG. The results suggest that normally, when bound to the ECM, APP functions to promote neurite outgrowth and/or cell survival. Loss of this normal trophic function might occur in AD, when APP is proteolytically processed via the amyloidogenic pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1993.tb23047.x
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  • 5
    Electronic Resource
    Electronic Resource
    Chromogranin A: Secretion of Processed Products from the Stimulated Retrogradely Perfused Bovine Adrenal Gland (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neuroendocrinology 5 (1993), S. 0 
    Details
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Chromogranin A (CGA) is a member of a family of highly acidic proteins co-stored and co-secreted with adrenaline and noradrenaline in the adrenal medulla. A number of biologically active fragments of CGA (CGAFs) have been characterized including a group of small N-terminal fragments collectively named vasostatins due to their vascular inhibitory activity. In the present study, the release of CGAFs, including CGA N-terminal fragments, from the isolated, retrogradely perfused bovine adrenal gland, has been studied under basal conditions and during nerve stimulation and perfusion with acetylcholine. The CGAFs were characterized by SDS-PAGE followed by immunoblotting with antisera to specific sequences within the CGA molecule. Many different CGAFs were released during stimulation of the glands. Antisera to CGA1–40 and CGA44–76 detected a 7 kD protein whose release was increased during stimulation. This component co-migrated with synthetic CGA1–76, was not immunoreactive to antisera to CGA79–113 or CGA124–143, and was seen whether or not the serine protease inhibitor aprotinin was present in the perfusion medium. The release of an ∼ 18 kD component, which stained with antisera to CGA1–40, CGA44–76 and CGA79–113, but not to chromostatin (CGA124–143), was also increased during stimulation. Components of 22 kD and larger were detected with antisera to chromostatin, but not with antisera to CGA1–40, CGA44–78 and CGA79–113. Two of these components of 22 to 24 kD were enhanced during nerve stimulation in the presence of aprotinin. The results indicate that processed Chromogranin A fragments are secreted from the bovine adrenal medulla during stimulation of chromaffin cells. The major fragments secreted appear to be the N-terminal fragments of CGA, CGA1–76 and CGA1–113, which would arise as a result of processing of CGA at the first and second pairs of basic amino acids. A number of larger CGAFs, possibly containing the chromostatin sequence CGA124–143 at their N-terminal, and components similar in size to intact CGA and to proteoglycan forms of CGA, are also secreted from the perfused bovine adrenal gland during stimulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2826.1993.tb00502.x
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  • 6
    Electronic Resource
    Electronic Resource
    Expression of dimeric and tetrameric acetylcholinesterase isoforms on the surface of cultured bovine adrenal chromaffin cells (1994)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 55 (1994), S. 398-407 
    Details
    ISSN: 0730-2312
    Keywords: protein transport ; chromaffin cell ; organophosphorus ; GPI-linked ; phosphatidyl-inositol-specific phospholipase C ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Acetylcholinesterase is a highly polymorphic enzyme, which can be anchored to the cell surface through several different mechanisms. Dimeric (G2) acetylcholinesterase isoforms are attached by a glycosylphosphatidyl-inositol (GPI) linkage, whereas tetrameric (G4) forms are linked through a 20 kilodalton hydrophobic subunit. Although cells of haemopoietic origin contain large amounts of G2 GPI-linked acetylcholinesterase, most tissues express only trace amounts of this isoform. We examined the expression of acetylcholinesterase isoforms in cultured bovine adrenal medullary chromaffin cells. Two major isoforms (G2 and G4) were identified on the cell surface. The G2 isoform, which accounted for approximately half the cell-surface enzyme activity, was linked to the membrane through a GPI anchor. After treatment with diisopropylfluorophosphate to completely inhibit cellular acetylcholinesterase, the G4 isoform was found to be resynthesised and transported to the cell surface more rapidly than the G2 isoform. As the addition of GPI anchors is known to be a very rapid step, this finding suggested that the G2 and G4 isoforms might be transported to the cell surface by two different mechanisms. This conclusion was supported by results from subcellular fractionation experiments. The ratio of G4/G2 membrane-bound acetylcholinesterase varied between different subcellular fractions. The membrane-bound G2 isoform was greatly enriched in a high-speed “microsomal” fraction. G4 acetylcholinesterase is known to be actively secreted by chromaffin cells in culture. Although the G4 isoform was present on the cell surface, most of the secreted enzyme was derived from an intracellular pool. Thus, it is unlikely that the cell-surface G4 isoform contributes significantly to the pool of secreted enzyme. Instead, the expression of two different membrane-bound isoforms may provide a means by which chromaffin cells can target the enzyme to different locations on the cell surface. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240550318
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