101
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Schubert P, Ogata T, Miyazaki H, Marchini C, Ferroni S, Rudolphi K. Pathological immuno-reactions of glial cells in Alzheimer's disease and possible sites of interference. JOURNAL OF NEURAL TRANSMISSION. SUPPLEMENTUM 1998; 54:167-74. [PMID: 9850925 DOI: 10.1007/978-3-7091-7508-8_16] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A significant role of a pathological glial cell activation in the pathogenesis of Alzheimer's disease is supported by the growing evidence that inflammatory proteins, which are produced by reactive astrocytes, promote the transformation of diffuse beta-amyloid deposits into the filamentous, neurotoxic form. A number of vicious circles, driven by the release of TNF-a and free oxygen radicals from microglial cells, may cause an upregulated microglial activation and their production of interleukin-1 which triggers, secondarily, the crucial activation of astrocytes. Reactive functional changes of glial cells seem to be controlled by an altered balance of the second messengers Ca2+ and cAMP and can be counterregulated by the endogenous cell modulator adenosine which strengthens the cAMP-dependent signalling chain. A further reinforcement of the homeostatic adenosine effects on glial cells by pharmaca, such as propentofylline, may add to neuroprotection in Alzheimer's disease.
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Affiliation(s)
- P Schubert
- Department of Neuromorphology, Max Planck Institute for Neurobiology, Martinsried, Federal Republic of Germany
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102
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Buxbaum JD, Liu KN, Luo Y, Slack JL, Stocking KL, Peschon JJ, Johnson RS, Castner BJ, Cerretti DP, Black RA. Evidence that tumor necrosis factor alpha converting enzyme is involved in regulated alpha-secretase cleavage of the Alzheimer amyloid protein precursor. J Biol Chem 1998; 273:27765-7. [PMID: 9774383 DOI: 10.1074/jbc.273.43.27765] [Citation(s) in RCA: 703] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The amyloid protein, Abeta, which accumulates in the brains of Alzheimer patients, is derived by proteolysis of the amyloid protein precursor (APP). APP can undergo endoproteolytic processing at three sites, one at the amino terminus of the Abeta domain (beta-cleavage), one within the Abeta domain (alpha-cleavage), and one at the carboxyl terminus of the Abeta domain (gamma-cleavage). The enzymes responsible for these activities have not been unambiguously identified. By the use of gene disruption (knockout), we now demonstrate that TACE (tumor necrosis factor alpha converting enzyme), a member of the ADAM family (a disintegrin and metalloprotease-family) of proteases, plays a central role in regulated alpha-cleavage of APP. Our data suggest that TACE may be the alpha-secretase responsible for the majority of regulated alpha-cleavage in cultured cells. Furthermore, we show that inhibiting this enzyme affects both APP secretion and Abeta formation in cultured cells.
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Affiliation(s)
- J D Buxbaum
- Departments of Psychiatry and Neurobiology, Mount Sinai School of Medicine, New York, New York 10029, USA.
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103
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Garlind A, Nilsson E, Palmblad J. Calcium ion transients in neutrophils from patients with sporadic Alzheimer's disease. Neurosci Lett 1998; 255:95-8. [PMID: 9835223 DOI: 10.1016/s0304-3940(98)00716-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abnormalities involving intracellular calcium homeostasis have been detected in Alzheimer's disease brain and fibroblasts as well as presenilin-1 mutation-bearing cells. In the present study we investigated inositol(1,4,5)trisphosphate-mediated calcium transients as well as calcium responses via mechanisms not related to surface receptors in Alzheimer's disease polymorphonuclear (PMN) granulocytes, using the tripeptide formyl-methionyl-leucyl-phenyl alanine (fMLP) and calcium ionophore ionomycin, respectively. fMLP elicited a biphasic response with an initial, fast increase in intracellular free calcium concentrations followed by a second, lower phase with no significant differences in either maximal response or time course between Alzheimer's disease granulocytes and controls. Similarly, the calcium signal elicited after ionomycin exposure was unchanged in Alzheimer's disease PMN. In conclusion, these results indicate that calcium mobilization from intracellular stores and via cross-membrane mechanisms is intact in Alzheimer's disease granulocytes.
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Affiliation(s)
- A Garlind
- Department of Clinical Neuroscience and Family Medicine, Karolinska Institute, Huddinge University Hospital, Sweden
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104
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Buxbaum JD, Choi EK, Luo Y, Lilliehook C, Crowley AC, Merriam DE, Wasco W. Calsenilin: a calcium-binding protein that interacts with the presenilins and regulates the levels of a presenilin fragment. Nat Med 1998; 4:1177-81. [PMID: 9771752 DOI: 10.1038/2673] [Citation(s) in RCA: 268] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Most early-onset familial Alzheimer disease (AD) cases are caused by mutations in the highly related genes presenilin 1 (PS1) and presenilin 2 (PS2). Presenilin mutations produce increases in beta-amyloid (Abeta) formation and apoptosis in many experimental systems. A cDNA (ALG-3) encoding the last 103 amino acids of PS2 has been identified as a potent inhibitor of apoptosis. Using this PS2 domain in the yeast two-hybrid system, we have identified a neuronal protein that binds calcium and presenilin, which we call calsenilin. Calsenilin interacts with both PS1 and PS2 in cultured cells, and can regulate the levels of a proteolytic product of PS2. Thus, calsenilin may mediate the effects of wild-type and mutant presenilins on apoptosis and on Abeta formation. Further characterization of calsenilin may lead to an understanding of the normal role of the presenilins and of the role of the presenilins in Alzheimer disease.
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Affiliation(s)
- J D Buxbaum
- Department of Psychiatry, Mount Sinai School of Medicine, New York, New York 10029, USA.
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105
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Kurumatani T, Fastbom J, Bonkale WL, Bogdanovic N, Winblad B, Ohm TG, Cowburn RF. Loss of inositol 1,4,5-trisphosphate receptor sites and decreased PKC levels correlate with staging of Alzheimer's disease neurofibrillary pathology. Brain Res 1998; 796:209-21. [PMID: 9689471 DOI: 10.1016/s0006-8993(98)00347-3] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Inositol 1,4,5-trisphosphate (IP3), inositol 1,3,4,5-tetrakisphosphate (IP4) and protein kinase C (PKC) play important roles in the phosphoinositide hydrolysis signal transducing pathway. Several studies have shown severe deficits in both IP3 receptor levels and PKC levels and activity in Alzheimer's disease brain, although the relationship of these changes to disease pathology is poorly understood. In the present study, we determined the autoradiographic localization of [3H]IP3 and [3H]IP4 binding to their calcium mobilizing receptor sites and [3H]phorbol 12,13-dibutyrate ([3H]PDBu) binding to PKC in sections of entorhinal cortex/hippocampal formation and cerebellum from 24 cases that had been staged for Alzheimer's disease-related neurofibrillary changes and amyloid deposition according to Braak and Braak [Acta Neuropathol. Berl., 82 (1991) 239-259]. Results indicated that [3H]IP3 binding showed a trend towards a decline with staging for neurofibrillary changes in the entorhinal region (0.05 < P < 0.10, ANOVA) and subiculum (0.05 < P < 0.10). In the former region, [3H]IP3 binding showed a significant decline with staging for amyloid deposition (P < 0.05). [3H]IP3 binding in the CA1 region showed statistically significant declines with respect to both neurofibrillary changes and amyloid staging (P < 0.05). [3H]IP3 binding levels in the other hippocampal subregions were too low to quantify accurately. The binding of [3H]IP4 showed no significant changes with either neurofibrillary changes or amyloid staging in any of the regions investigated. In contrast, [3H]PDBu binding showed significant declines with neurofibrillary staging in the entorhinal region (P < 0.01), subiculum (P < 0.001), CA1 (P < 0.001), CA2 (P < 0.001), CA3 (P < 0.001) and CA4 (P < 0.0001) regions and the dentate gyrus (P < 0.0001). Of these regions, only the subiculum showed a significant decline of [3H]PDBu binding with amyloid staging. There were no significant neurofibrillary or amyloid stage-related changes in either [3H]IP3, [3H]IP4 or [3H]PDBu binding in the molecular layer of the cerebellum. These findings suggest that reduced IP3 receptor and PKC levels in the entorhinal cortex/hippocampal formation reflect and may be important for the progression of Alzheimer's disease neurofibrillary pathology. The data also suggests that hippocampal IP3 receptor loss is related to the extent of amyloid deposition.
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Affiliation(s)
- T Kurumatani
- Karolinska Institute, Department of Clinical Neuroscience and Family Medicine, Huddinge, Sweden
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106
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Protein kinase C activation increases release of secreted amyloid precursor protein without decreasing Abeta production in human primary neuron cultures. J Neurosci 1998. [PMID: 9526007 DOI: 10.1523/jneurosci.18-08-02907.1998] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Overexpression and altered metabolism of amyloid precursor protein (APP) resulting in increased 4 kDa amyloid beta peptide (Abeta) production are believed to play a major role in Alzheimer's disease (AD). Therefore, reducing Abeta production in the brain is a possible therapy for AD. Because AD pathology is fairly restricted to the CNS of humans, we have established human cerebral primary neuron cultures to investigate the metabolism of APP. In many cell lines and rodent primary neuron cultures, phorbol ester activation of protein kinase C (PKC) increases the release of the secreted large N-terminal fragment of amyloid precursor protein (sAPP) and decreases Abeta release (; ; ). In contrast, we find that PKC activation in human primary neurons increases the rate of sAPP release and the production of APP C-terminal fragments and 4 kDa Abeta. Our results indicate species- and cell type-specific regulation of APP metabolism. Therefore, our results curtail the use of PKC activators in controlling human brain Abeta levels.
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107
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LeBlanc AC, Koutroumanis M, Goodyer CG. Protein kinase C activation increases release of secreted amyloid precursor protein without decreasing Abeta production in human primary neuron cultures. J Neurosci 1998; 18:2907-13. [PMID: 9526007 PMCID: PMC6792603] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Overexpression and altered metabolism of amyloid precursor protein (APP) resulting in increased 4 kDa amyloid beta peptide (Abeta) production are believed to play a major role in Alzheimer's disease (AD). Therefore, reducing Abeta production in the brain is a possible therapy for AD. Because AD pathology is fairly restricted to the CNS of humans, we have established human cerebral primary neuron cultures to investigate the metabolism of APP. In many cell lines and rodent primary neuron cultures, phorbol ester activation of protein kinase C (PKC) increases the release of the secreted large N-terminal fragment of amyloid precursor protein (sAPP) and decreases Abeta release (; ; ). In contrast, we find that PKC activation in human primary neurons increases the rate of sAPP release and the production of APP C-terminal fragments and 4 kDa Abeta. Our results indicate species- and cell type-specific regulation of APP metabolism. Therefore, our results curtail the use of PKC activators in controlling human brain Abeta levels.
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Affiliation(s)
- A C LeBlanc
- Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada H3A 2T6
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108
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Racchi M, Ianna P, Binetti G, Trabucchi M, Govoni S. Bradykinin-induced amyloid precursor protein secretion: a protein kinase C-independent mechanism that is not altered in fibroblasts from patients with sporadic Alzheimer's disease. Biochem J 1998; 330 ( Pt 3):1271-5. [PMID: 9494096 PMCID: PMC1219272 DOI: 10.1042/bj3301271] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We treated human skin fibroblasts with bradykinin (BK) and observed a concentration-dependent increase in the release of soluble amyloid precursor protein (sAPP). The estimated EC50 for the observed effect is 2.8 nM, which is of the same order of magnitude as the reported Kd of BK binding in human skin fibroblasts. The effect of BK on sAPP secretion appears to be dependent on interaction of the ligand with the B2 type of BK receptors but independent of activation of protein kinase C. We also show that sAPP release after BK treatment in fibroblasts from patients with sporadic Alzheimer's disease is not different from control cells and is paralleled by equivalent levels of inositol trisphosphate production. A discussion of the differences from previously published work focuses on the possible divergent alterations in transduction systems in fibroblasts from patients with familial and sporadic Alzheimer's disease. Our results are the first example of receptor-mediated sAPP release in human skin fibroblasts and the first demonstration of the co-existence of protein kinase C-dependent and -independent mechanisms in these cells.
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Affiliation(s)
- M Racchi
- Laboratory of Cellular and Molecular Neurobiology, Alzheimer's Disease Unit, I.R.C.C.S. San Giovanni di Dio, Sacred Heart Hospital-FBF, Brescia, Italy
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109
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Regulation of amyloid precursor protein catabolism involves the mitogen-activated protein kinase signal transduction pathway. J Neurosci 1998. [PMID: 9390997 DOI: 10.1523/jneurosci.17-24-09415.1997] [Citation(s) in RCA: 99] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Catabolic processing of the amyloid precursor protein (APP) is subject to regulatory control by protein kinases. We hypothesized that this regulation involves sequential activation of the enzymes mitogen-activated protein kinase kinase (MEK) and extracellular signal-regulated protein kinase (ERK). In the present investigation, we provide evidence that MEK is critically involved in regulating APP processing by both nerve growth factor and phorbol esters. Western blot analysis of the soluble N-terminal APP derivative APPs demonstrated that the synthetic MEK inhibitor PD 98059 antagonized nerve growth factor stimulation of both APPs production and ERK activation in PC12 cells. Moreover, PD 98059 inhibited phorbol ester stimulation of APPs production and activation of ERK in both human embryonic kidney cells and cortical neurons. Furthermore, overexpression of a kinase-inactive MEK mutant inhibited phorbol ester stimulation of APP secretion and activation of ERK in human embryonic kidney cell lines. Most important, PD 98059 antagonized phorbol ester-mediated inhibition of Abeta secretion from cells overexpressing human APP695 carrying the "Swedish mutation." Taken together, these data indicate that MEK and ERK may be critically involved in protein kinase C and nerve growth factor regulation of APP processing. The mitogen-activated protein kinase cascade may provide a novel target for altering catabolic processing of APP.
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110
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Mills J, Laurent Charest D, Lam F, Beyreuther K, Ida N, Pelech SL, Reiner PB. Regulation of amyloid precursor protein catabolism involves the mitogen-activated protein kinase signal transduction pathway. J Neurosci 1997; 17:9415-22. [PMID: 9390997 PMCID: PMC6573401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/1997] [Revised: 09/17/1997] [Accepted: 09/28/1997] [Indexed: 02/05/2023] Open
Abstract
Catabolic processing of the amyloid precursor protein (APP) is subject to regulatory control by protein kinases. We hypothesized that this regulation involves sequential activation of the enzymes mitogen-activated protein kinase kinase (MEK) and extracellular signal-regulated protein kinase (ERK). In the present investigation, we provide evidence that MEK is critically involved in regulating APP processing by both nerve growth factor and phorbol esters. Western blot analysis of the soluble N-terminal APP derivative APPs demonstrated that the synthetic MEK inhibitor PD 98059 antagonized nerve growth factor stimulation of both APPs production and ERK activation in PC12 cells. Moreover, PD 98059 inhibited phorbol ester stimulation of APPs production and activation of ERK in both human embryonic kidney cells and cortical neurons. Furthermore, overexpression of a kinase-inactive MEK mutant inhibited phorbol ester stimulation of APP secretion and activation of ERK in human embryonic kidney cell lines. Most important, PD 98059 antagonized phorbol ester-mediated inhibition of Abeta secretion from cells overexpressing human APP695 carrying the "Swedish mutation." Taken together, these data indicate that MEK and ERK may be critically involved in protein kinase C and nerve growth factor regulation of APP processing. The mitogen-activated protein kinase cascade may provide a novel target for altering catabolic processing of APP.
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Affiliation(s)
- J Mills
- Kinsmen Laboratory of Neurological Research, Department of Psychiatry, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3
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111
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Abstract
Proteolytic processing of beta-amyloid precursor protein (APP) is believed to be fundamental to the understanding of Alzheimer's disease. The identities and the regulatory elements of the proteases involved in the process, known as alpha/beta/gamma secretases, are unclear. In this study, by examining reported data, we found some indications suggesting that the putative alpha-secretase may be a calcium-dependent protease, and that this enzyme may play a primary role in the regulation of APP processing. Based on this, we proposed a model for the membrane orientations of the secretases for further discussions.
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Affiliation(s)
- M Chen
- Department of Pharmacology and Therapeutics, University of South Florida College of Medicine, Tampa 33612, USA.
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112
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Kim SH, Kim YK, Jeong SJ, Haass C, Kim YH, Suh YH. Enhanced release of secreted form of Alzheimer's amyloid precursor protein from PC12 cells by nicotine. Mol Pharmacol 1997; 52:430-6. [PMID: 9281605 DOI: 10.1124/mol.52.3.430] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
There is mounting evidence indicating that overexpression or aberrant processing of amyloid precursor protein (betaAPP) is causally related to Alzheimer's disease. betaAPP is principally cleaved within the amyloid beta protein domain to release a large soluble ectodomain (betaAPPs) that has been known to have a wide range of trophic and protective functions. Activation of phospholipase C-coupled receptors has been shown to increase the release of betaAPPs through protein kinase C and calcium. Here we have examined whether nicotine can modulate the expression and processing of betaAPP in PC12 cells. Treatment of PC12 cells with nicotine increased the release of a carboxyl-terminally truncated, secreted form of betaAPP into the conditioned medium without affecting the expression level of betaAPP mRNA. The effect of nicotine on the secretion of betaAPPs is concentration (>50 microM)- and time (>2 hr)-dependent and attenuated by cotreatment with either mecamylamine, a specific nicotinic receptor antagonist, or EGTA, a calcium chelator, indicating calcium entry through the neuronal nicotinic acetylcholine receptor is essential in enhanced betaAPPs release by nicotine. However, nicotine did not significantly change the amyloid beta protein secretion from Swedish mutant betaAPP-transfected PC12 cells. These results imply that nicotinic receptor agonist might be beneficial in the treatment of Alzheimer's disease by not only supplementing the deficient cholinergic neurotransmission but also stimulating the release of betaAPPs.
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Affiliation(s)
- S H Kim
- Department of Pharmacology, College of Medicine, Neuroscience Research Institute, Seoul National University, Seoul, Korea
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113
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Ehrenstein G, Galdzicki Z, Lange GD. The choline-leakage hypothesis for the loss of acetylcholine in Alzheimer's disease. Biophys J 1997; 73:1276-80. [PMID: 9284295 PMCID: PMC1181027 DOI: 10.1016/s0006-3495(97)78160-8] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
We present a hypothesis for the loss of acetylcholine in Alzheimer's disease that is based on two recent experimental results: that beta-amyloid causes leakage of choline across cell membranes and that decreased production of acetylcholine increases the production of beta-amyloid. According to the hypothesis, an increase in beta-amyloid concentration caused by proteolysis of the amyloid precursor protein results in an increase in the leakage of choline out of cells. This leads to a reduction in intracellular choline concentration and hence a reduction in acetylcholine production. The reduction in acetylcholine production, in turn, causes an increase in the concentration of beta-amyloid. The resultant positive feedback between decreased acetylcholine and increased beta-amyloid accelerates the loss of acetylcholine. We compare the predictions of the choline-leakage hypothesis with a number of experimental observations. We also approximate it with a pair of ordinary differential equations. The solutions of these equations indicate that the loss of acetylcholine is very sensitive to the initial rate of beta-amyloid production.
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Affiliation(s)
- G Ehrenstein
- Biophysics Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
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114
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Ye C, Ho-Pao CL, Kanazirska M, Quinn S, Rogers K, Seidman CE, Seidman JG, Brown EM, Vassilev PM. Amyloid-beta proteins activate Ca(2+)-permeable channels through calcium-sensing receptors. J Neurosci Res 1997; 47:547-54. [PMID: 9067864 DOI: 10.1002/(sici)1097-4547(19970301)47:5<547::aid-jnr10>3.0.co;2-v] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The amyloid-beta peptides (A beta) are produced in excess in Alzheimer's disease (AD) and may contribute to neuronal dysfunction and degeneration. This study provides strong evidence for a novel cellular target for the actions of A beta, the phospholipase C-coupled, extracellular Ca(2+)-sensing receptor (CaR). We demonstrate that A beta(s) produce a CaR-mediated activation of a Ca(2+)-permeable, nonselective cation channel (NCC), probably via elevation in cytosolic Ca2+ (Cai), in cultured hippocampal pyramidal neurons from normal rats and from wild type mice but not those from mice with targeted disruption of the CaR gene (CaR -/-). A beta(s) also activate NCC in CaR-transfected but not in nontransfected human embryonic kidney (HEK293) cells. Thus aggregates of A beta deposited on hippocampal neurons in AD could appropriately activate the CaR, stimulating Ca(2+)-permeable channels and causing sustained elevation of Cai with resultant neuronal dysfunction.
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Affiliation(s)
- C Ye
- Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
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115
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Petryniak MA, Wurtman RJ, Slack BE. Elevated intracellular calcium concentration increases secretory processing of the amyloid precursor protein by a tyrosine phosphorylation-dependent mechanism. Biochem J 1996; 320 ( Pt 3):957-63. [PMID: 9003386 PMCID: PMC1218021 DOI: 10.1042/bj3200957] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Secretory cleavage of the amyloid precursor protein (APP), a process that releases soluble APP derivatives (APPs) into the extracellular space, is stimulated by the activation of muscarinic receptors coupled to phosphoinositide hydrolysis. The signalling pathways involved in the release process exhibit both protein kinase C- and protein tyrosine phosphorylation-dependent components [Slack, Breu, Petryniak, Srivastava and Wurtman (1995) J. Biol. Chem. 270, 8337-8344]. The possibility that elevations in intracellular Ca2+ concentration initiate the tyrosine phosphorylation-dependent release of APPs was examined in human embryonic kidney cells expressing muscarinic m3 receptors. Inhibition of protein kinase C with the bisindolylmaleimide GF 109203X decreased the carbachol-evoked release of APPs by approx. 30%, as shown previously. The residual response was further decreased, in an additive manner, by the Ca2+ chelator EGTA, or by the tyrosine kinase inhibitor tyrphostin A25. The Ca2+ ionophore, ionomycin, like carbachol, stimulated both the release of APPs and the tyrosine phosphorylation of several proteins, one of which was identified as paxillin, a component of focal adhesions. The effects of ionomycin on APPs release and on protein tyrosine phosphorylation were concentration-dependent, and occurred over similar concentration ranges; both effects were inhibited only partly by GF 109203X, but were abolished by EGTA or by tyrosine kinase inhibitors. The results demonstrate for the first time that ionophore-induced elevations in intracellular Ca2+ levels elicit APPs release via increased tyrosine phosphorylation. Part of the increase in APPs release evoked by muscarinic receptor activation might be attributable to a similar mechanism.
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Affiliation(s)
- M A Petryniak
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge 02139, USA
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116
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Pittel Z, Heldman E, Barg J, Haring R, Fisher A. Muscarinic control of amyloid precursor protein secretion in rat cerebral cortex and cerebellum. Brain Res 1996; 742:299-304. [PMID: 9117408 DOI: 10.1016/s0006-8993(96)01031-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
It was previously shown by us and by others that activation of muscarinic acetylcholine receptors evoke amyloid precursor protein (APP) secretion in various cell lines. Here we examined if such muscarinic control of APP secretion occurs also in normal brain tissues. We found that the secretion of APP from rat cerebrocortical slices (rich in M1 receptors) was significantly increased by K+ depolarization, the non-selective agonist, carbachol (CCh), and the M1-selective agonist, AF102B. CCh also increased APP secretion from cerebellar slices (rich in M2 receptors) while AF102B had no significant effect in this brain region. Despite of its stimulatory effect on APP release in the cerebellum, CCh had no effect on phosphoinositide (PI) metabolism in this brain region. In the cerebral cortex PI metabolism was significantly increased by CCh but only partially increased by AF102B. These results suggest that APP secretion in the brain is mediated via muscarinic receptors. In the cerebral cortex APP secretion seems to be regulated via M1 receptors. Our results also suggest that PI metabolism is not a pronounced step in mediating APP processing.
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Affiliation(s)
- Z Pittel
- Israel Institute for Biological Research, Ness-Ziona, Israel
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117
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Desdouits F, Buxbaum JD, Desdouits-Magnen J, Nairn AC, Greengard P. Amyloid beta peptide formation in cell-free preparations. Regulation by protein kinase C, calmodulin, and calcineurin. J Biol Chem 1996; 271:24670-4. [PMID: 8798734 DOI: 10.1074/jbc.271.40.24670] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Amyloid beta peptide (Abeta) is a short peptide that is the major constituent of the amyloid plaques and cerebrovascular amyloid deposits found in Alzheimer's disease. The lack of availability of a cell-free system in which to study Abeta formation has limited our understanding of the molecular mechanisms involved in its production. We report here the reconstitution of such a cell-free system. The reconstituted Abeta formation was temperature-dependent and required ATP. Preincubation with purified protein kinase C (PKC) induced a pronounced inhibition of Abeta formation, similar to that observed in intact cells upon stimulation of PKC. The calmodulin antagonists W-7 and trifluoperazine inhibited Abeta formation and enhanced the action of PKC in both the cell-free system and intact cells. A role for the calcium/calmodulin-activated protein phosphatase calcineurin in the regulation of Abeta formation was demonstrated using a specific peptide inhibitor of calcineurin in vitro as well as cyclosporin A, a cell-permeant inhibitor of calcineurin, in intact cells. Our results suggest that a single substrate might mediate opposing actions of PKC and calcineurin in the regulation of Abeta formation.
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Affiliation(s)
- F Desdouits
- Laboratory of Molecular and Cellular Neuroscience and the Zachary and Elizabeth M. Fisher Center for Research on Alzheimer Disease, The Rockefeller University, New York, New York 10021, USA
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118
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Nitsch RM, Deng M, Growdon JH, Wurtman RJ. Serotonin 5-HT2a and 5-HT2c receptors stimulate amyloid precursor protein ectodomain secretion. J Biol Chem 1996; 271:4188-94. [PMID: 8626761 DOI: 10.1074/jbc.271.8.4188] [Citation(s) in RCA: 166] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Alzheimer's disease amyloid consists of amyloid beta-peptides (Abeta) derived from the larger precursor amyloid precursor protein (APP). Non-amyloidogenic APP processing involves regulated cleavage within the Abeta domain followed by secretion of the ectodomain (APPs). APPs secretion can be stimulated by muscarinic acetylcholine receptors coupled to phospholipases and kinases. To determine whether other receptor classes can regulate APP processing, we examined the relation between serotonin receptors and APPs secretion. Serotonin increased APPs release 3-4-fold in 3T3 cells stably overexpressing 5-HT2aR or 5-HT2cR. The increase was dose-dependent and was blocked by serotoninergic antagonists. Phorbol esters also increased APPs secretion, but neither kinase inhibitors nor down-regulation of PKC blocked the serotonin-induced increase in APPs secretion. Thus PKC is not necessary to stimulate APPs secretion. Phospholipase A2 (PLA2) inhibitors blocked the 5-HT2aR-mediated increase in APPs secretion, suggesting a role of PLA2 in coupling 5-HT2aR to APP processing. In contrast, coupling of 5-HT2cR to APPs secretion involved both PKC and PLA2. Serotonin also stimulated the release of the APLP2 ectodomain, suggesting that additional members of the APP multigene family are processed via similar regulated pathways. Inasmuch as generation of APPs precludes the formation of amyloidogenic derivatives, serotonin receptors provide a novel pharmacological target to reduce these derivatives in Alzheimer's disease.
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Affiliation(s)
- R M Nitsch
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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119
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Abstract
APP processing appears to be under complex regulation. This regulation is apparently important under both normal and pathological conditions. Of direct clinical interest is the observation that A beta formation can be regulated by various means. This raises the possibility that altered APP processing may cause an increase in A beta formation in AD, and suggests that it may be possible to regulate the production of A beta as a therapeutic approach in AD. As an example of the utility of the latter approach, consider a patient carrying the Swedish APP mutation. If it is true that the cause of AD in such a patient is due to increased A beta production, then decreasing A beta production should delay the onset of the disease. Even in individuals where increased A beta formation is not the cause of AD but there is some other causes, such as the presence of an allele of apolipoprotein E which causes A beta accumulation and hence synaptic loss, decreasing A beta formation may be beneficial. It is of course a very long way from in vitro experiments to therapy. The current emphasis on studying APP processing in vivo represents the next step towards this goal.
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Affiliation(s)
- J D Buxbaum
- Laboratory of Molecular and Cellular Neuroscience, Rockefeller University, New York, New York, USA 10021
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120
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121
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Larner AJ. Physiological and pathological interrelationships of amyloid beta peptide and the amyloid precursor protein. Bioessays 1995; 17:819-24. [PMID: 8763834 DOI: 10.1002/bies.950170912] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Amyloid beta peptide (beta A4) accumulates as plaques in the brains of individuals with Alzheimer's disease and Down's syndrome, and may contribute to the cognitive decline that is a feature of these diseases. beta A4 is a normal product of cell metabolism, derived from the amyloid precursor protein (APP), but the biological functions of these molecules are not fully known. A hypothetical, descriptive model of the biological interrelationships between beta A4 and APP is presented. APPs, the soluble form of APP, which is released at the neuronal surface, and beta A4 are envisaged as physiological ligands which have reciprocal paracrine effects on neuronal growth and neurite extension. Differential expression of these factors, manifest as changes in the APPs: beta A4 ratio, may therefore have growth-promoting or growth-inhibiting effects on neurons. These effects may be mediated through separate cell-surface interactions but common intracellular effector systems, such as calcium and protein kinase C. In turn, the intracellular events may control the relative production of each ligand from APP through negative feedback loops. Disturbances of these control mechanisms may permit pathological overproduction, and hence accumulation, of beta A4. Such a model may also have therapeutic implications.
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Affiliation(s)
- A J Larner
- University of Cambridge, Department of Anatomy, UK
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122
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Lee RK, Wurtman RJ, Cox AJ, Nitsch RM. Amyloid precursor protein processing is stimulated by metabotropic glutamate receptors. Proc Natl Acad Sci U S A 1995; 92:8083-7. [PMID: 7644542 PMCID: PMC41291 DOI: 10.1073/pnas.92.17.8083] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Stimulation of muscarinic m1 or m3 receptors can, by generating diacylglycerol and activating protein kinase C, accelerate the breakdown of the amyloid precursor protein (APP) to form soluble, nonamyloidogenic derivatives (APPs), as previously shown. This relationship has been demonstrated in human glioma and neuroblastoma cells, as well as in transfected human embryonic kidney 293 cells and PC-12 cells. We now provide evidence that stimulation of metabotropic glutamate receptors (mGluRs), which also are coupled to phosphatidylinositol 4,5-bisphosphate hydrolysis, similarly accelerates processing of APP into nonamyloidogenic APPs. This process is demonstrated both in hippocampal neurons derived from fetal rats and in human embryonic kidney 293 cells transfected with cDNA expression constructs encoding the mGluR 1 alpha subtype. In hippocampal neurons, both an mGluR antagonist, L-(+)-2-amino-3-phosphonopropionic acid, and an inhibitor of protein kinase C, GF 109203X, blocked the APPs release evoked by glutamate receptor stimulation. Ionotropic glutamate agonists, N-methyl-D-aspartate or S(-)-5-fluorowillardiine, failed to affect APPs release. These data show that selective mGluR agonists that initiate signal-transduction events can regulate APP processing in bona fide primary neurons and transfected cells. As glutamatergic neurons in the cortex and hippocampus are damaged in Alzheimer disease, amyloid production in these regions may be enhanced by deficits in glutamatergic neurotransmission.
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Affiliation(s)
- R K Lee
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge 02139, USA
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123
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Li QX, Evin G, Small DH, Multhaup G, Beyreuther K, Masters CL. Proteolytic processing of Alzheimer's disease beta A4 amyloid precursor protein in human platelets. J Biol Chem 1995; 270:14140-7. [PMID: 7775475 DOI: 10.1074/jbc.270.23.14140] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The processing of amyloid precursor protein (APP) and production of beta A4 amyloid are events likely to influence the development and progression of Alzheimer's disease, since beta A4 is the major constituent of amyloid deposited in this disorder. Our previous studies showed that human platelets contain full-length APP (APPFL) and are a suitable substrate to study normal APP processing. In the present study, we show that a 22-kDa beta A4-containing carboxyl-terminal fragment (22-CTF) of APP is present in unstimulated platelets. Both APPFL and 22-CTF are proteolytically degraded when platelets are activated with thrombin, collagen, or calcium ionophore A23187. Complete cleavage of APPFL and 22-CTF require the presence of extracellular calcium. Following stimulation in the presence of calcium, a new CTF of 17 kDa is generated, and the NH2-terminal epitope of beta A4 amyloid is lost. Preincubation of platelets with the cell-permeable cysteine protease inhibitors calpeptin, (2S,3S)-trans-epoxysuccinyl-L-leucyl-amido-3-methylbutane ethyl ester (E64d), Na alpha-p-tosyl-L-lysine chloromethyl ketone, or calcium chelator EGTA before platelet stimulation inhibits the degradation of both APPFL and 22-CTF. Divalent metal ions including zinc, copper, and cobalt inhibit the degradation of APPFL and 22-CTF. This study suggests that a calcium-dependent neutral cysteine protease is involved in the proteolytic processing of an amyloidogenic species of APP in human platelets.
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Affiliation(s)
- Q X Li
- Department of Pathology, University of Melbourne, Parkville, Victoria, Australia
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124
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Slack BE, Breu J, Petryniak MA, Srivastava K, Wurtman RJ. Tyrosine phosphorylation-dependent stimulation of amyloid precursor protein secretion by the m3 muscarinic acetylcholine receptor. J Biol Chem 1995; 270:8337-44. [PMID: 7713942 DOI: 10.1074/jbc.270.14.8337] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Stimulation of m1 and m3 muscarinic acetylcholine receptors, which are coupled to phosphoinositide hydrolysis and protein kinase C activation, has been shown to increase the release of soluble amyloid precursor protein derivatives (APPs). The effect is mimicked by phorbol esters, which directly activate protein kinase C. Using human embryonic kidney cells expressing individual muscarinic receptor subtypes, we found that stimulation of APPs release by the muscarinic agonist carbachol was only partially reduced by a specific inhibitor of protein kinase C (the bisindolylmaleimide GF 109203X), while the response to phorbol 12-myristate 13-acetate (PMA) was abolished. The increase in APPs release elicited by carbachol and PMA was accompanied by elevated tyrosine phosphorylation of several proteins and reduced by tyrosine kinase inhibitors; GF 109203X significantly reduced the stimulation of tyrosine phosphorylation by carbachol and PMA. Inhibition of protein tyrosine phosphatases by vanadyl hydroperoxide markedly increased cellular tyrosine phosphorylation and enhanced APPs release as effectively as PMA and carbachol. Direct phosphorylation of amyloid precursor protein on tyrosine residues following treatment with carbachol, PMA, or vanadyl hydroperoxide was not observed. The results implicate both tyrosine phosphorylation and protein kinase C-dependent mechanisms in the regulation of APPs release by G protein-coupled receptors, and suggest that carbachol and PMA increase APPs release from human embryonic kidney cells expressing m3 muscarinic receptors via partially divergent pathways that converge at a tyrosine phosphorylation-dependent step.
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Affiliation(s)
- B E Slack
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge 02139, USA
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125
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Wolf BA, Wertkin AM, Jolly YC, Yasuda RP, Wolfe BB, Konrad RJ, Manning D, Ravi S, Williamson JR, Lee VM. Muscarinic regulation of Alzheimer's disease amyloid precursor protein secretion and amyloid beta-protein production in human neuronal NT2N cells. J Biol Chem 1995; 270:4916-22. [PMID: 7876266 DOI: 10.1074/jbc.270.9.4916] [Citation(s) in RCA: 149] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The Alzheimer amyloid precursor protein (APP) undergoes complex processing resulting in the production of a 4-kDa amyloid peptide (A beta) which has been implicated in the pathogenesis of Alzheimer's disease. Recent studies have shown that cells can secrete carboxyl terminus truncated APP derivatives (APP-S) in response to physiological stimulus. We have used human central nervous system neurons (NT2N) derived from a teratocarcinoma cell line (NT2) to study the signal transduction pathways involved in APP-S secretion and A beta production. Muscarinic receptors (m2 and m3) as well as the heterotrimeric GTP-binding protein Gq and the beta 1 isoform of phospholipase C were present in NT2N neurons. Stimulation of the muscarinic receptor with carbachol resulted in phospholipase C activation as shown by a transient increase in the second messengers 1,2-diacyl-sn-glycerol and inositol 1,4,5-trisphosphate. Carbachol also caused an increase in intracellular Ca2+ levels measured in single NT2N neurons. Under these conditions, carbachol caused a time-dependent 2-fold increase in APP-S secretion into the medium. In contrast, prolonged treatment with carbachol caused a decrease in A beta production into the medium. These results suggest that APP-S secretion and A beta production in NT2N neurons are regulated by the muscarinic/phospholipase C signal transduction pathway. Furthermore, activation of this pathway results in dissociation of APP-S secretion and A beta production.
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Affiliation(s)
- B A Wolf
- Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia 19104
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126
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Haass C, Koo EH, Capell A, Teplow DB, Selkoe DJ. Polarized sorting of beta-amyloid precursor protein and its proteolytic products in MDCK cells is regulated by two independent signals. J Biophys Biochem Cytol 1995; 128:537-47. [PMID: 7860629 PMCID: PMC2199885 DOI: 10.1083/jcb.128.4.537] [Citation(s) in RCA: 109] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Progressive cerebral deposition of the amyloid (A beta) beta-protein is an early and invariant feature of Alzheimer's disease. A beta is derived by proteolysis from the membrane-spanning beta-amyloid precursor protein (beta APP). beta APP is processed into various secreted products, including soluble beta APP (APPs), the 4-kD A beta peptide, and a related 3-kD peptide (p3). We analyzed the mechanisms regulating the polarized basolateral sorting of beta APP and its proteolytic derivatives in MDCK cells. Deletion of the last 32 amino acids (residues 664-695) of the beta APP cytoplasmic tail had no influence on either the constitutive approximately 90% level of basolateral sorting of surface beta APP, or the strong basolateral secretion of APPs, A beta, and p3. However, deleting the last 42 amino acids (residues 654-695) or changing tyrosine 653 to alanine altered the distribution of cell surface beta APP so that approximately 40-50% of the molecules were inserted apically. In parallel, A beta was now secreted from both surfaces. Surprisingly, this change in surface beta APP had no influence on the basolateral secretion of APPs and p3. This result suggests that most beta APP molecules which give rise to APPs in MDCK cells are cleaved intracellularly before reaching the surface. Consistent with this conclusion, we readily detected intracellular APPs in carbonate extracts of isolated membrane vesicles. Moreover, ammonium chloride treatment resulted in the equal secretion of APPs into both compartments, as occurs with other non-membranous, basolaterally secreted proteins, but it did not influence the polarity of cell surface beta APP. These results demonstrate that in epithelial cells two independent mechanisms mediate the polarized trafficking of beta APP holoprotein and its major secreted derivative (APPs) and that A beta peptides are derived in part from beta APP holoprotein targeted to the cell surface by a signal that includes tyrosine 653.
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Affiliation(s)
- C Haass
- Department of Neurology, Harvard Medical School, Boston, Massachusetts 02115
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127
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Arribas J, Massagué J. Transforming growth factor-alpha and beta-amyloid precursor protein share a secretory mechanism. J Biophys Biochem Cytol 1995; 128:433-41. [PMID: 7844156 PMCID: PMC2120346 DOI: 10.1083/jcb.128.3.433] [Citation(s) in RCA: 126] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Cleavage and release of membrane protein ectodomains, a regulated process that affects many cell surface proteins, remains largely uncharacterized. To investigate whether cell surface proteins are cleaved through a shared mechanism or through multiple independent mechanisms, we mutagenized Chinese hamster ovary (CHO) cells and selected clones that were unable to cleave membrane-anchored transforming growth factor alpha (TGF-alpha). The defect in TGF-alpha cleavage in these clones is most apparent upon cell treatment with the protein kinase C (PKC) activator PMA, which stimulates TGF-alpha cleavage in wild-type cells. The mutant clones do not have defects in TFG-alpha expression, transport to the cell surface or turnover. Concomitant with the loss of TGF-alpha cleavage, these clones have lost the ability to cleave many structurally unrelated membrane proteins in response to PMA. These proteins include beta-amyloid precursor protein (beta-APP), whose cleavage into a secreted form avoids conversion into the amyloidogenic peptide A beta, and a group of cell surface proteins whose release into the medium is stimulated by PMA in wild type CHO cells but not in mutants. The mutations prevent cleavage by PKC-dependent as well as PKC-independent mechanisms, and thus affect an essential component that functions downstream of these various signaling mechanisms. We propose that regulated cleavage and secretion of membrane protein ectodomains is mediated by a common system whose components respond to multiple activators and act on susceptible proteins of diverse structure and function.
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Affiliation(s)
- J Arribas
- Cell Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York 10021
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128
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Vasilakos JP, Carroll RT, Emmerling MR, Doyle PD, Davis RE, Kim KS, Shivers BD. Interleukin-1 beta dissociates beta-amyloid precursor protein and beta-amyloid peptide secretion. FEBS Lett 1994; 354:289-92. [PMID: 7957941 DOI: 10.1016/0014-5793(94)01142-7] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A heightened production of interleukin 1 beta (IL-1 beta) has been reported in microglial-associated amyloid deposits in Alzheimer's disease (AD) brains. These plaques are composed predominantly of beta/A4 peptide derived from beta-amyloid precursor protein (beta APP). We demonstrate that short-term (1 h) IL-1 beta-treatment increases beta APPs secretion and concomitantly decreases cell-associated beta APP in human H4 neuroglioma cells. Long-term (5 h) IL-1 beta treatment did not alter secreted or cell-associated beta APP content. In contrast, the secretion of beta/A4-containing epitope was not affected by short-term IL-1 beta stimulation; however, long-term IL-1 beta treatment decreased the amount of beta/A4-containing epitope secreted from the cells. These results show that IL-1 beta modifies the processing and secretion of beta APP to exacerbate perhaps the neuropathology of AD.
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Affiliation(s)
- J P Vasilakos
- Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Co., Ann Arbor, MI 48105
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