Human BACE Forms Dimers and Colocalizes with APP

Schmechel, Ariane; Strauß, Markus; Schlicksupp, Andrea; Pipkorn, Rüdiger; Haass, Christian; Bayer, Thomas A.; Multhaup, Gerd

doi:10.1074/jbc.m402785200

Cited by 73 publications

(59 citation statements)

References 56 publications

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“…RTK-induced BACE internalization results in accumulation of BACE in endosomes where the acidic environment could provide optimum pH BACE activity. In addition, it has been reported that APP and BACE are co-internalized into endosomes, leading to enhanced APP cleavage there [57][58][59][60]. Thus, the abnormally enlarged endosomes observed in the early stages of AD [17] might be due to abnormal internalization of BACE and APP, leading to enhanced Aβ production.…”

Section: Discussionmentioning

confidence: 99%

Receptor tyrosine kinases positively regulate BACE activity and Amyloid-β production through enhancing BACE internalization

et al. 2007

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Amyloid-β (Aβ) peptide, the primary constituent of senile plaques in Alzheimer's disease (AD), is generated by β-secretase-and γ-secretase-mediated sequential proteolysis of the amyloid precursor protein (APP). The aspartic protease, β -site APP cleavage enzyme (BACE), has been identified as the main β-secretase in brain but the regulation of its activity is largely unclear. Here, we demonstrate that both BACE activity and subsequent Aβ production are enhanced after stimulation of receptor tyrosine kinases (RTKs), such as the receptors for epidermal growth factor (EGF) and nerve growth factor (NGF), in cultured cells as well as in mouse hippocampus. Furthermore, stimulation of RTKs also induces BACE internalization into endosomes and Golgi apparatus. This enhancement of BACE activity and Aβ production upon RTK activation could be specifically inhibited by Src family kinase inhibitors and by depletion of endogenous c-Src with RNAi, and could be mimicked by over-expressed c-Src. Moreover, blockage of BACE internalization by a dominant negative form of Rab5 also abolished the enhancement of BACE activity and Aβ production, indicating the requirement of BACE internalization for the enhanced activity. Taken together, our study presents evidence that BACE activity and Aβ production are under the regulation of RTKs and this is achieved via RTK-stimulated BACE internalization, and suggests that an aberration of such regulation might contribute to pathogenic Aβ production.

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Section: Discussionmentioning

confidence: 99%

Receptor tyrosine kinases positively regulate BACE activity and Amyloid-β production through enhancing BACE internalization

et al. 2007

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“…The ordered dimerization of APP has also been implicated in cell-cell interactions (29). It has been reported that dimerization depends on zinc binding (18,30), heparin binding (16), or the simultaneous interaction of several sites within the APP molecule (31) including its transmembrane domain (29) and that it is functionally associated with the concurrent dimerization of the β-site APP cleaving enzyme (28,(31)(32)(33). Recently, Gralle et al corroborated the physiological importance of APP dimerization using single molecule FRET methods (27).…”

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confidence: 99%

Structure and biochemical analysis of the heparin-induced E1 dimer of the amyloid precursor protein

Dahms

Hoefgen

Roeser

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

108

128

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The authors note the following: "Due to an error in the evaluation of the raw ITC-data, we reported the wrong sign for the enthalpy values and correspondingly incorrect entropy values. The correct values are as follows: at pH 5.7: ΔH −54 ± 4 kJ/ mol, ΔS −68 ± 14 J/mol K and at pH 7.2: ΔH −62 ± 6 kJ/mol and ΔS −98 ± 18 J/mol K (Table 3)." The authors note that on page 5381, left column, first paragraph, line 9 "Two E1 entities dimerize upon their interaction with heparin, requiring 8-12 sugar rings to form the heparin-bridged APP-E1 dimer in an endothermic and pH-dependent process that is characterized by a low micromolar dissociation constant" should have read "Two E1 entities dimerize upon their interaction with heparin, requiring 8-12 sugar rings to form the heparin-bridged APP-E1 dimer in an exothermic and pH-dependent process that is characterized by a low micromolar dissociation constant." On page 5384, right column, third paragraph, line 23 "This reaction is driven by high entropy contributions of around 300 J/mol · K, probably resulting from the release of associated ions and water molecules upon heparin binding, as also observed for other heparin-binding proteins (reviewed, e.g., in ref. 39)" should have read "This reaction is driven by significant enthalpic contributions, probably arising from protein-protein interactions, also observed for other heparin-binding proteins (reviewed, e.g., in ref. 39)." This error does not affect the conclusions of the article.

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“…3). To exclude a direct influence of the peptide on BACE enzyme activity, we assayed soluble BACE enriched from cell culture supernatant (20) in the presence of the loop-WT peptide (data not shown). Because we failed to detect any changes in activity (22) with or without the loop-WT peptide, and the peptide can specifically bind to APP18 -350 (see Biacore data in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Cloning, expression, and enrichment of the ␤-site APP cleaving enzyme (BACE) ectodomain were performed as described previously (20).…”

Section: Methodsmentioning

confidence: 99%

Homophilic Interactions of the Amyloid Precursor Protein (APP) Ectodomain Are Regulated by the Loop Region and Affect β-Secretase Cleavage of APP

Kaden

Munter

Joshi

et al. 2008

Journal of Biological Chemistry

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We found previously by fluorescence resonance energy transfer experiments that amyloid precursor protein (APP) homodimerizes in living cells. APP homodimerization is likely to be mediated by two sites of the ectodomain and a third site within the transmembrane sequence of APP. We have now investigated the role of the N-terminal growth factor-like domain in APP dimerization by NMR, biochemical, and cell biological approaches. Under nonreducing conditions, the N-terminal domain of APP formed SDSlabile and SDS-stable complexes. The presence of SDS was sufficient to convert native APP dimers entirely into monomers. Addition of an excess of a synthetic peptide (APP residues 91-116) containing the disulfide bridge-stabilized loop inhibited crosslinking of pre-existing SDS-labile APP ectodomain dimers. Surface plasmon resonance analysis revealed that this peptide specifically bound to the N-terminal domain of APP and that binding was entirely dependent on the oxidation of the thiol groups. By solution-state NMR we detected small chemical shift changes indicating that the loop peptide interacted with a large protein surface rather than binding to a defined pocket. Finally, we studied the effect of the loop peptide added to the medium of living cells. Whereas the levels of ␣-secretory APP increased, soluble ␤-cleaved APP levels decreased. Because A␤40 and A␤42 decreased to similar levels as soluble ␤-cleaved APP, we conclude either that ␤-secretase binding to APP was impaired or that the peptide allosterically affected APP processing. We suggest that APP acquires a loop-mediated homodimeric state that is further stabilized by interactions of hydrophobic residues of neighboring domains.The amyloid precursor protein (APP) 3 of Alzheimer disease is one of the best studied type I cell surface glycoproteins with a proposed regulatory role in cell adhesion in the peripheral and central nervous system (1). APP is physiologically processed by either ␣-or ␤-secretases, which release the soluble ectodomain (sAPP␣ or sAPP␤) from the cell surface (2-5). Alternatively, the membrane-bound fragment APP-C-terminal fragment, which is derived from ␤-secretase cleavage, is further processed by the ␥-secretase into the cytoplasmic domain of APP and amyloid ␤-peptides (A␤) of varying lengths (6 -9). Recently, elucidation of the ␥-secretase cleavage mechanism has revealed that a conserved GXXXG motif in the transmembrane sequence of APP mediates homophilic helix-helix interactions and has an important role in the processing of A␤40/42 into shorter A␤ species, i.e. A␤38, A␤37, A␤35, and A␤34 (7).Unraveling structural features of APP by NMR spectroscopy and x-ray crystallography has led to the identification of specific regions that function as subdomains (see Fig. 1A). The extracellular N-terminal domain of APP has been dissected into the E1 region consisting of the N-terminal growth factor-like domain (GFLD) followed by the copper-binding domain (CuBD) (10). An acidic region (residues 190 -264) precedes the carbohydrate domain, which contains...

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Human BACE Forms Dimers and Colocalizes with APP

Cited by 73 publications

References 56 publications

Receptor tyrosine kinases positively regulate BACE activity and Amyloid-β production through enhancing BACE internalization

Receptor tyrosine kinases positively regulate BACE activity and Amyloid-β production through enhancing BACE internalization

Structure and biochemical analysis of the heparin-induced E1 dimer of the amyloid precursor protein

Homophilic Interactions of the Amyloid Precursor Protein (APP) Ectodomain Are Regulated by the Loop Region and Affect β-Secretase Cleavage of APP

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