Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027819 (neuroblastoma)
 27,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The voltage-gated sodium channel beta2-subunit (beta2) is a member of the IgCAM superfamily and serves as both an adhesion molecule and an auxiliary subunit of the voltage-gated sodium channel. Here we found that beta2 undergoes ectodomain shedding followed by presenilin (PS)-dependent gamma-secretase-mediated cleavage. 12-O-Tetradecanoylphorbol-13-acetate treatment or expression of an alpha-secretase enzyme, ADAM10, resulted in ectodomain cleavage of beta2 in Chinese hamster ovary cells. Subsequent cleavage of the remaining 15-kDa C-terminal fragment (beta2-CTF) was independently inhibited by three specific gamma-secretase inhibitors, expression of the dominant negative form of PS1, and in PS1/PS2 knock-out cells. gamma-Secretase inhibitor treatment also increased endogenous beta2-CTF levels in neuroblastoma cells and mouse primary neuronal cultures. In a cell-free gamma-secretase assay, we detected gamma-secretase activity-dependent generation of a 12 kDa beta2 intracellular domain (ICD), which was loosely associated with the membrane fraction. To assess the functional role of beta2 processing by gamma-secretase, we tested whether N-[N-(3,5-difluorophenylacetyl-l-alanyl)]-S-phenylglycine t-butylester (DAPT), a specific gamma-secretase inhibitor, would alter beta2-mediated cell adhesion and migration. We found that DAPT inhibited cell-cell aggregation and migration in a wound healing assay carried out with Chinese hamster ovary cells expressing beta2. DAPT also reduced migration of neuroblastoma cells in a modified Boyden chamber assay. Since DAPT treatment resulted in increased beta2-CTF levels, we also tested whether beta2-CTFs or beta2-ICDs would directly affect cell migration by overexpressing recombinant proteins. Interestingly, elevated levels of beta2-CTFs, but not ICDs, also blocked cell migration by 81 to 93%. Together, our findings show for the first time that beta2 is a PS/gamma-secretase substrate and gamma-secretase mediated cleavage of beta2-CTF is required for cell-cell adhesion and migration of beta2-expressing cells.
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PMID:Presenilin/gamma-secretase-mediated cleavage of the voltage-gated sodium channel beta2-subunit regulates cell adhesion and migration. 1583 46

Cleavage of the amyloid precursor protein (APP) within the amyloid-beta (Abeta) sequence by the alpha-secretase prevents the formation of toxic Abeta peptides. It has been shown that the disintegrin-metalloproteinases ADAM10 and TACE (ADAM17) act as alpha-secretases and stimulate the generation of a soluble neuroprotective fragment of APP, APPsalpha. Here we demonstrate that the related APP-like protein 2 (APLP2), which has been shown to be essential for development and survival of mice, is also a substrate for both proteinases. Overexpression of either ADAM10 or TACE in HEK293 cells increased the release of neurotrophic soluble APLP2 severalfold. The strongest inhibition of APLP2 shedding in neuroblastoma cells was observed with an ADAM10-preferring inhibitor. Transgenic mice with neuron-specific overexpression of ADAM10 showed significantly increased levels of soluble APLP2 and its C-terminal fragments. To elucidate a possible regulatory mechanism of APLP2 shedding in the neuronal context, we examined retinoic acid-induced differentiation of neuroblastoma cells. Retinoic acid treatment of two neuroblastoma cell lines upregulated the expression of both APLP2 and ADAM10, thus leading to an increased release of soluble APLP2.
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PMID:Shedding of the amyloid precursor protein-like protein APLP2 by disintegrin-metalloproteinases. 1627 45

In the non-amyloidogenic pathway the alpha-secretase cleaves the amyloid precursor protein (APP) within the sequence of Abeta-peptides and precludes their formation. In addition, alpha-secretase cleavage releases an N-terminal extracellular domain with neurotrophic and neuroprotective properties. The disintegrin metalloproteinase ADAM10 has been shown to act as alpha-secretase in vivo, to prevent amyloid plaque formation and hippocampal defects in an Alzheimer disease mouse model. An increase in alpha-secretase activity therefore is an attractive strategy for treatment of AD and may be achieved by modulating selective signalling pathways. Functional characterization of the human ADAM10 promoter showed that it contains several binding elements for transcription factors which are regulated by extracellular ligands. Retinoic acid (RA) was identified as an inducer of human ADAM10 promoter activity. In human neuroblastoma cell lines RA treatment upregulated the expression of both the alpha-secretase ADAM10 and its substrates APP and the related APP-like-protein 2 (APLP2), and led to an enhanced secretion of their extracellular domains. Furthermore, G protein-coupled receptors (GPCRs) localized in brain areas affected by AD were investigated. Activation of the PAC1 receptor by the neuropeptide PACAP was identified as an approach for upregulation of the alpha-secretase pathway.
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PMID:Alpha-secretase as a therapeutic target. 1790 44

Alpha-secretase (alpha-secretase), cleaves the amyloid precursor protein (APP) within the amyloid-beta (Abeta) sequence, resulting in the release of a secreted fragment of APP (alphaAPPs) and precluding Abeta generation. We investigated the effects of the acetylcholinesterase inhibitor, huperzine A (Hup A), on APP processing and Abeta generation in human neuroblastoma SK-N-SH cells overexpressing wild-type human APP695. Hup A dose-dependently (0-10 microM) increased alphaAPPs release. Therefore, we evaluated two alpha-secretase candidates, a disintegrin and metalloprotease (ADAM) 10 and ADAM17 in Hup A-induced non-amyloidogenic APP metabolism. Hup A enhanced the level of ADAM10, and the inhibitor of tumor necrosis factor-alpha converting enzyme (TACE)/ADAM17 inhibited the Hup A-induced rise in alphaAPPs levels, further suggesting Hup A directed APP metabolism toward the non-amyloidogenic alpha-secretase pathway. Hup A had no effect on Abeta generation in this cell line. The steady-state levels of full-length APP and cell viability were unaffected by Hup A. Alpha-APPs release induced by Hup A treatment was significantly reduced by muscarinic acetylcholine receptor antagonists (particularly by an M1 antagonist), protein kinase C (PKC) inhibitors, GF109203X and calphostin C, and the mitogen-activated kinase kinase (MEK) inhibitors, U0126 and PD98059. Furthermore, Hup A markedly increased the phosphorylation of p44/p42 mitogen-activated protein (MAP) kinase, which was blocked by treatment with U0126 and PD98059. In addition, Hup A inhibited acetylcholinesterase activity by 20% in neuroblastoma cells. Our results indicate that the activation of muscarinic acetylcholine receptors, PKC and MAP kinase may be involved in Hup A-induced alphaAPPs secretion in neuroblastoma cells and suggest multiple pharmacological mechanisms of Hup A regarding the treatment of Alzheimer's disease (AD).
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PMID:Huperzine A regulates amyloid precursor protein processing via protein kinase C and mitogen-activated protein kinase pathways in neuroblastoma SK-N-SH cells over-expressing wild type human amyloid precursor protein 695. 1794 34

Retinoic acid stimulates alpha-secretase processing of amyloid precursor protein (APP) and decreases beta-secretase cleavage that leads to amyloid-beta formation. Here, we investigated the effect of retinoic acid on the two putative alpha-secretases, the disintegrin metalloproteinases ADAM10 and TACE, and the beta-site cleaving enzyme BACE1, in human neuroblastoma SH-SY5Y cells. Western blot analysis showed that exposure to retinoic acid resulted in significantly increased levels of ADAM10 and TACE, suggesting that regulation of alpha-secretases causes the effects on APP processing. The presence of the phosphatidylinositol 3-kinase inhibitor LY 294002 selectively reduced the effect on ADAM10 protein levels but not on ADAM10 mRNA levels as determined by RT-PCR. On the other hand, the effect on TACE was shown to be dependent on protein kinase C, since it was completely blocked in the presence of the inhibitor bisindolylmaleimide XI. Our data indicate that different signalling pathways are involved in retinoic acid-induced up-regulation of the secretases.
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PMID:PI3-K- and PKC-dependent up-regulation of APP processing enzymes by retinoic acid. 1798 85

Alzheimer Disease is the most common chronic neurodegenerative disorder associated with aging. Nevertheless, its pharmacological therapy is still an unresolved issue. In double-blind controlled studies, acetyl-L-carnitine (ALC) demonstrated beneficial effects on Alzheimer's disease. However, the mechanisms behind its neuroprotective ability remain to be fully established. In this study, the effect of acetyl-L-carnitine on amyloid precursor protein (APP) metabolism was investigated by in vitro models, both in a neuroblastoma cell line and in primary hippocampal cultures. We found that ALC treatment stimulates alpha-secretase activity and physiological APP metabolism. In particular, ALC favors the delivery of ADAM10 (a disintegrin and metalloproteinase 10, the most accredited candidate for alpha-secretase) to the post-synaptic compartment, and consequently positively modulates its enzymatic activity towards APP. Our findings suggest that the benefits of ALC reported in previous clinical studies are underscored by the specific biological mechanism of this compound on APP metabolism. In fact, ALC can directly influence the primary event in Alzheimer's disease pathogenesis, i.e. the Amyloid beta cascade, promoting alpha-secretase activity and directly affecting the release of the non amyloidogenic metabolite.
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PMID:Modulatory effect of acetyl-L-carnitine on amyloid precursor protein metabolism in hippocampal neurons. 1880 59

Late-onset Alzheimer's disease is often connected with nutritional misbalance, such as enhanced cholesterol intake, deficiency in polyunsaturated fatty acids, or hypovitaminosis. The alpha-secretase ADAM10 has been found to be regulated by retinoic acid, the bioreactive metabolite of vitamin A. Here we show that retinoids induce gene expression of ADAM10 and alpha-secretase activity by nonpermissive retinoid acid receptor/retinoid X receptor (RAR/RXR) heterodimers, whereby alpha- and beta-isotypes of RAR play a major role. However, ligands of other RXR binding partners, such as the vitamin D receptor, do not stimulate alpha-secretase activity. On the basis of these findings, we examined the effect of synthetic retinoids and found a strong enhancement of nonamyloidogenic processing of the amyloid precursor protein by the vitamin A analog acitretin: it stimulated ADAM10 promoter activity with an EC(50) of 1.5 microM and led to an increase of mature ADAM10 protein that resulted in a two- to three-fold increase of the ratio between alpha- and beta-secretase activity in neuroblastoma cells. The alpha-secretase stimulation by acitretin was completely inhibited by the ADAM10-specific inhibitor GI254023X. Intracerebral injection of acitretin in APP/PS1-21 transgenic mice led to a reduction of Abeta(40) and Abeta(42). The results of this study may have clinical relevance because acitretin has been approved for the treatment of psoriasis since 1997 and found generally safe for long-term use in humans.
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PMID:Up-regulation of the alpha-secretase ADAM10 by retinoic acid receptors and acitretin. 1914 97

The cellular prion protein (PrP(C)) is essential for the pathogenesis and transmission of prion diseases. PrP(C) is bound to the plasma membrane via a glycosylphosphatidylinositol anchor, although a secreted, soluble form has also been identified. Previously we reported that PrP(C) is subject to ectodomain shedding from the membrane by zinc metalloproteinases with a similar inhibition profile to those involved in shedding the amyloid precursor protein. Here we have used gain-of-function (overexpression) and loss-of-function (small interfering RNA knockdown) experiments in cells to identify the ADAMs (a disintegrin and metalloproteinases) involved in the ectodomain shedding of PrP(C). These experiments revealed that ADAM9 and ADAM10, but not ADAM17, are involved in the shedding of PrP(C) and that ADAM9 exerts its effect on PrP(C) shedding via ADAM10. Using dominant negative, catalytically inactive mutants, we show that the catalytic activity of ADAM9 is required for its effect on ADAM10. Mass spectrometric analysis revealed that ADAM10, but not ADAM9, cleaved PrP between Gly(228) and Arg(229), three residues away from the site of glycosylphosphatidylinositol anchor attachment. The shedding of another membrane protein, the amyloid precursor protein beta-secretase BACE1, by ADAM9 is also mediated via ADAM10. Furthermore, we show that pharmacological inhibition of PrP(C) shedding or activation of both PrP(C) and PrP(Sc) shedding by ADAM10 overexpression in scrapie-infected neuroblastoma N2a cells does not alter the formation of proteinase K-resistant PrP(Sc). Collectively, these data indicate that although PrP(C) can be shed through the action of ADAM family members, modulation of PrP(C) or PrP(Sc) ectodomain shedding does not regulate prion conversion.
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PMID:Role of ADAMs in the ectodomain shedding and conformational conversion of the prion protein. 1956 38

Using mass spectrometry, we identified ADAM10 (a membrane-associated metalloproteinase) as a partner for TSPAN12, a tetraspanin protein. TSPAN12-ADAM10 interaction was confirmed by reciprocal coimmunoprecipitation in multiple tumor cell lines. TSPAN12, to a greater extent than other tetraspanins (CD81, CD151, CD9, and CD82), associated with ADAM10 but not with ADAM17. Overexpression of TSPAN12 enhanced ADAM10-dependent shedding of amyloid precursor protein (APP) in MCF7 (breast cancer) and SH-SY5Y (neuroblastoma) cell lines. Conversely, siRNA ablation of endogenous TSPAN12 markedly diminished APP proteolysis in both cell lines. Furthermore, TSPAN12 overexpression enhanced ADAM10 prodomain maturation, whereas TSPAN12 ablation diminished ADAM10 maturation. A palmitoylation-deficient TSPAN12 mutant failed to associate with ADAM10, inhibited ADAM10-dependent proteolysis of APP, and inhibited ADAM10 maturation, most likely by interfering with endogenous wild-type TSPAN12. In conclusion, TSPAN12 serves as a novel and robust partner for ADAM10 and promotes ADAM10 maturation, thereby facilitating ADAM10-dependent proteolysis of APP. This novel mode of regulating APP cleavage is of relevance to Alzheimer's disease therapy.
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PMID:Tetraspanin12 regulates ADAM10-dependent cleavage of amyloid precursor protein. 1958 94

Substantial evidence supports a central role of Abeta in the pathogenesis of Alzheimer's disease (AD). We have demonstrated that FLZ, a synthetic cyclic analogue of natural squamosamide, exhibits neuroprotective actions in cells and mouse models, suggesting future investigation of FLZ as a candidate compound for the treatment of AD. In this study, we found that the production of amyloid-beta (Abeta) was reduced by FLZ in Abeta-expressing neuroblastoma cells, and correlated with an increase in the soluble alpha-secretase derived fragment of the amyloid-beta protein precursor (sAbetaPPalpha) in the medium. Moreover, the active form of ADAM10 and AbetaPP were elevated at the cell surface of FLZ-treated cells, consistent with an enhanced co-localization of ADAM10 and AbetaPP on the membrane. Pretreatment with brefeldin, a protein trafficking inhibitor, blocked FLZ-induced translocation of ADAM10 to the cell surface and release of sAbetaPPalpha to the culture medium. Furthermore, oral administration of FLZ to APPswe/PS1 transgenic mice significantly reduced the levels of Abeta, paralleling with activation of ADAM10, in the hippocampus. In silico prediction indicates that the structure of FLZ is compatible with the drug-like rules for absorption and permeability. These findings suggest that FLZ reduces Abeta production by promoting AbetaPP non-amyloidogenic alpha-secretase processing. As such, FLZ may have therapeutic potential for the treatment of AD.
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PMID:A natural squamosamide derivative FLZ reduces amyloid-beta production by increasing non-amyloidogenic AbetaPP processing. 1962 48


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