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1.
Martina?Pigoni Johanna?Wanngren Peer-Hendrik?Kuhn Kathryn?M.?Munro Jenny?M.?Gunnersen Hiroshi?Takeshima Regina?Feederle Iryna?Voytyuk Bart?De Strooper Mikail?D.?Levasseur Brian?J.?Hrupka Stephan?A.?Müller Stefan?F.?Lichtenthaler
Background
The protease BACE1 (beta-site APP cleaving enzyme) is a major drug target in Alzheimer’s disease. However, BACE1 therapeutic inhibition may cause unwanted adverse effects due to its additional functions in the nervous system, such as in myelination and neuronal connectivity. Additionally, recent proteomic studies investigating BACE1 inhibition in cell lines and cultured murine neurons identified a wider range of neuronal membrane proteins as potential BACE1 substrates, including seizure protein 6 (SEZ6) and its homolog SEZ6L.Methods and results
We generated antibodies against SEZ6 and SEZ6L and validated these proteins as BACE1 substrates in vitro and in vivo. Levels of the soluble, BACE1-cleaved ectodomain of both proteins (sSEZ6, sSEZ6L) were strongly reduced upon BACE1 inhibition in primary neurons and also in vivo in brains of BACE1-deficient mice. BACE1 inhibition increased neuronal surface levels of SEZ6 and SEZ6L as shown by cell surface biotinylation, demonstrating that BACE1 controls surface expression of both proteins. Moreover, mass spectrometric analysis revealed that the BACE1 cleavage site in SEZ6 is located in close proximity to the membrane, similar to the corresponding cleavage site in SEZ6L. Finally, an improved method was developed for the proteomic analysis of murine cerebrospinal fluid (CSF) and was applied to CSF from BACE-deficient mice. Hereby, SEZ6 and SEZ6L were validated as BACE1 substrates in vivo by strongly reduced levels in the CSF of BACE1-deficient mice.Conclusions
This study demonstrates that SEZ6 and SEZ6L are physiological BACE1 substrates in the murine brain and suggests that sSEZ6 and sSEZ6L levels in CSF are suitable markers to monitor BACE1 inhibition in mice.2.
Amyloid precursor protein traffics from the Golgi directly to early endosomes in an Arl5b‐ and AP4‐dependent pathway 下载免费PDF全文
Wei Hong Toh Jing Zhi A. Tan Khalisah L. Zulkefli Fiona J. Houghton Paul A. Gleeson 《Traffic (Copenhagen, Denmark)》2017,18(3):159-175
The intracellular trafficking and proteolytic processing of the membrane‐bound amyloid precursor protein (APP) are coordinated events leading to the generation of pathogenic amyloid‐beta (Aβ) peptides. The membrane transport of newly synthesized APP from the Golgi to the endolysosomal system is not well defined, yet it is likely to be critical for regulating its processing by β‐secretase (BACE1) and γ‐secretase. Here, we show that the majority of newly synthesized APP is transported from the trans‐Golgi network (TGN) directly to early endosomes and then subsequently to the late endosomes/lysosomes with very little transported to the cell surface. We show that Arl5b, a small G protein localized to the TGN, and AP4 are essential for the post‐Golgi transport of APP to early endosomes. Arl5b is physically associated with AP4 and is required for the recruitment of AP4, but not AP1, to the TGN. Depletion of either Arl5b or AP4 results in the accumulation of APP, but not BACE1, in the Golgi, and an increase in APP processing and Aβ secretion. These findings demonstrate that APP is diverted from BACE1 at the TGN for direct transport to early endosomes and that the TGN represents a site for APP processing with the subsequent secretion of Aβ. 相似文献
3.
The non‐peptidic δ‐opioid receptor agonist Tan‐67 mediates neuroprotection post‐ischemically and is associated with altered amyloid precursor protein expression,maturation and processing in mice 下载免费PDF全文
Jia‐Wei Min Yanying Liu David Wang Fangfang Qiao Hongmin Wang 《Journal of neurochemistry》2018,144(3):336-347
4.
Amyloid precursor protein (APP) modulates glutamate release via cytoplasmic and intravesicular interactions with the synaptic vesicle release machinery. The intravesicular domain, called ISVAID, contains the BACE1 cleavage site of APP. We have tested the functional significance of BACE1 processing of APP using App‐Swedish (Apps) knock‐in rats, which carry an App mutation that causes familial Alzheimer's disease (FAD) in humans. We show that in Apps rats, β‐cleavage of APP is favored over α‐cleavage. Apps rats show facilitated glutamate, but not GABA, release. Our data support the notion that APP tunes glutamate release, and that BACE1 cleavage of the ISVAID segment of APP facilitates this function. We define this phenomenon as BACE1 on APP‐dependent glutamate release (BAD‐Glu). Unsurprisingly, Apps rats show no evidence of AD‐related pathology at 15 days and 3 months of age, indicating that alterations in BAD‐Glu are not caused by pathological lesions. The evidence that a pathogenic APP mutation causes an early enhancement of BAD‐Glu suggests that alterations of BACE1 processing of APP in glutamatergic synaptic vesicles could contribute to dementia. 相似文献
5.
Kulandaivelu S. Vetrivel Xavier Meckler Ying Chen Phuong D. Nguyen Nabil G. Seidah Robert Vassar Philip C. Wong Masaki Fukata Maria Z. Kounnas Gopal Thinakaran 《The Journal of biological chemistry》2009,284(6):3793-3803
Alzheimer disease β-amyloid (Aβ) peptides are generated via
sequential proteolysis of amyloid precursor protein (APP) by BACE1 and
γ-secretase. A subset of BACE1 localizes to cholesterol-rich membrane
microdomains, termed lipid rafts. BACE1 processing in raft microdomains of
cultured cells and neurons was characterized in previous studies by disrupting
the integrity of lipid rafts by cholesterol depletion. These studies found
either inhibition or elevation of Aβ production depending on the extent
of cholesterol depletion, generating controversy. The intricate interplay
between cholesterol levels, APP trafficking, and BACE1 processing is not
clearly understood because cholesterol depletion has pleiotropic effects on
Golgi morphology, vesicular trafficking, and membrane bulk fluidity. In this
study, we used an alternate strategy to explore the function of BACE1 in
membrane microdomains without altering the cellular cholesterol level. We
demonstrate that BACE1 undergoes S-palmitoylation at four Cys
residues at the junction of transmembrane and cytosolic domains, and Ala
substitution at these four residues is sufficient to displace BACE1 from lipid
rafts. Analysis of wild type and mutant BACE1 expressed in BACE1 null
fibroblasts and neuroblastoma cells revealed that S-palmitoylation
neither contributes to protein stability nor subcellular localization of
BACE1. Surprisingly, non-raft localization of palmitoylation-deficient BACE1
did not have discernible influence on BACE1 processing of APP or secretion of
Aβ. These results indicate that post-translational
S-palmitoylation of BACE1 is not required for APP processing, and
that BACE1 can efficiently cleave APP in both raft and non-raft
microdomains.Alzheimer disease-associated β-amyloid
(Aβ)3 peptides
are derived from the sequential proteolysis of β-amyloid precursor
protein (APP) by β- and γ-secretases. The major β-secretase is
an aspartyl protease, termed BACE1 (β-site
APP-cleaving enzyme 1)
(1–4).
BACE1 cleaves APP within the extracellular domain of APP, generating the N
terminus of Aβ. In addition, BACE1 also cleaves to a lesser extent within
the Aβ domain between Tyr10 and Glu11
(β′-cleavage site). Processing of APP at these sites results in the
shedding/secretion of the large ectodomain (sAPPβ) and generating
membrane-tethered C-terminal fragments +1 and +11 (β-CTF)
(5). The multimeric
γ-secretase cleaves at multiple sites within the transmembrane domain of
β-CTF, generating C-terminal heterogeneous Aβ peptides (ranging in
length between 38 and 43 residues) that are secreted, as well as cytosolic APP
intracellular domains (6). In
addition to BACE1, APP can be cleaved by α-secretase within the Aβ
domain between Lys16 and Leu17, releasing sAPPα
and generating α-CTF. γ-Secretase cleavage of α-CTF
generates N-terminal truncated Aβ, termed p3.Genetic ablation of BACE1 completely abolishes Aβ production,
establishing BACE1 as the major neuronal enzyme responsible for initiating
amyloidogenic processing of APP
(4,
7). Interestingly, both the
expression and activity of BACE1 is specifically elevated in neurons adjacent
to senile plaques in brains of individuals with Alzheimer disease
(8). In the past few years
additional substrates of BACE1 have been identified that include APP
homologues APLP1 and APLP2 (9),
P-selectin glycoprotein ligand-1
(10), β-galactoside
α2,6-sialyltransferase
(11), low-density lipoprotein
receptor-related protein (12),
β-subunits of voltage-gated sodium channels
(13), and neuregulin-1
(14,
15), thus extending the
physiological function of BACE1 beyond Alzheimer disease pathogenesis.BACE1 is a type I transmembrane protein with a long extracellular domain
harboring a catalytic domain and a short cytoplasmic tail. BACE1 is
synthesized as a proenzyme, which undergoes post-translational modifications
that include removal of a pro-domain by a furin-like protease,
N-glycosylation, phosphorylation, S-palmitoylation, and
acetylation, during the transit in the secretory pathway
(16–20).
In non-neuronal cells the majority of BACE1 localizes to late Golgi/TGN and
endosomes at steady-state and a fraction of BACE1 also cycles between the cell
surface and endosomes (21).
The steady-state localization of BACE1 is consistent with the acidic pH
optimum of BACE1 in vitro, and BACE1 cleavage of APP is observed in
the Golgi apparatus, TGN, and endosomes
(22–25).
BACE1 endocytosis and recycling are mediated by the GGA family of adaptors
binding to a dileucine motif (496DISLL) in its cytoplasmic tail
(21,
26–31).
Phosphorylation at Ser498 within this motif modulates GGA-dependent
retrograde transport of BACE1 from endosomes to TGN
(21,
26–31).Over the years, a functional relationship between cellular cholesterol
level and Aβ production has been uncovered, raising the intriguing
possibility that cholesterol levels may determine the balance between
amyloidogenic and non-amyloidogenic processing of APP
(32–34).
Furthermore, several lines of evidence from in vitro and in
vivo studies indicate that cholesterol- and sphingolipid-rich membrane
microdomains, termed lipid rafts, might be the critical link between
cholesterol levels and amyloidogenic processing of APP. Lipid rafts function
in the trafficking of proteins in the secretory and endocytic pathways in
epithelial cells and neurons, and participate in a number of important
biological functions (35).
BACE1 undergoes S-palmitoylation
(19), a reversible
post-translational modification responsible for targeting a variety of
peripheral and integral membrane proteins to lipid rafts
(36). Indeed, a significant
fraction of BACE1 is localized in lipid raft microdomains in a
cholesterol-dependent manner, and addition of glycosylphosphatidylinositol
(GPI) anchor to target BACE1 exclusively to lipid rafts increases APP
processing at the β-cleavage site
(37,
38). Antibody-mediated
co-patching of cell surface APP and BACE1 has provided further evidence for
BACE1 processing of APP in raft microdomains
(33,
39). Components of the
γ-secretase complex also associate with detergent-resistant membrane
(DRM) fractions enriched in raft markers such as caveolin, flotillin, PrP, and
ganglioside GM1 (40). The
above findings suggest a model whereby APP is sequentially processed by BACE1
and γ-secretase in lipid rafts.Despite the accumulating evidence, cleavage of APP by BACE1 in non-raft
membrane regions cannot be unambiguously ruled out because of the paucity of
full-length APP (APP FL) and BACE1 in DRM isolated from adult brain and
cultured cells (41). Moreover,
it was recently reported that moderate reduction of cholesterol (<25%)
displaces BACE1 from raft domains, and increases BACE1 processing by promoting
the membrane proximity of BACE1 and APP in non-raft domains
(34). Nevertheless, this study
also found that BACE1 processing of APP is inhibited with further loss of
cholesterol (>35%), consistent with earlier studies
(32,
33). Nevertheless, given the
pleiotropic effects of cholesterol depletion on membrane properties and
vesicular trafficking of secretory and endocytic proteins
(42–47),
unequivocal conclusions regarding BACE1 processing of APP in lipid rafts
cannot be reached based on cholesterol depletion studies.In this study, we explored the function of BACE1 in lipid raft microdomains
without manipulating cellular cholesterol levels. In addition to the
previously reported S-palmitoylation sites
(Cys478/Cys482/Cys485) within the cytosolic
tail of BACE1 (19), we have
identified a fourth site (Cys474) within the transmembrane domain
of BACE1 that undergoes S-palmitoylation. A BACE1 mutant with Ala
substitution of all four Cys residues (BACE1-4C/A) fails to associate with DRM
in cultured cells, but is not otherwise different from wtBACE1 in terms of
protein stability, maturation, or subcellular localization. Surprisingly, APP
processing and Aβ generation were unaffected in cells stably expressing
the BACE1-4C/A mutant. Finally, we observed an increase in the levels of APP
CTFs in detergent-soluble fractions of BACE1-4C/A as compared with wtBACE1
cells. Thus, our data collectively indicate a non-obligatory role of
S-palmitoylation and lipid raft localization of BACE1 in
amyloidogenic processing of APP. 相似文献
6.
Madepalli K. Lakshmana Il-Sang Yoon Eunice Chen Elizabetta Bianchi Edward H. Koo David E. Kang 《The Journal of biological chemistry》2009,284(18):11863-11872
Accumulation of the amyloid β (Aβ) peptide derived from the
proteolytic processing of amyloid precursor protein (APP) is the defining
pathological hallmark of Alzheimer disease. We previously demonstrated that
the C-terminal 37 amino acids of lipoprotein receptor-related protein (LRP)
robustly promoted Aβ generation independent of FE65 and specifically
interacted with Ran-binding protein 9 (RanBP9). In this study we found that
RanBP9 strongly increased BACE1 cleavage of APP and Aβ generation. This
pro-amyloidogenic activity of RanBP9 did not depend on the KPI domain or the
Swedish APP mutation. In cells expressing wild type APP, RanBP9 reduced cell
surface APP and accelerated APP internalization, consistent with enhanced
β-secretase processing in the endocytic pathway. The N-terminal half of
RanBP9 containing SPRY-LisH domains not only interacted with LRP but also with
APP and BACE1. Overexpression of RanBP9 resulted in the enhancement of APP
interactions with LRP and BACE1 and increased lipid raft association of APP.
Importantly, knockdown of endogenous RanBP9 significantly reduced Aβ
generation in Chinese hamster ovary cells and in primary neurons,
demonstrating its physiological role in BACE1 cleavage of APP. These findings
not only implicate RanBP9 as a novel and potent regulator of APP processing
but also as a potential therapeutic target for Alzheimer disease.The major defining pathological hallmark of Alzheimer disease
(AD)2 is the
accumulation of amyloid β protein (Aβ), a neurotoxic peptide derived
from β- and γ-secretase cleavages of the amyloid precursor protein
(APP). The vast majority of APP is constitutively cleaved in the middle of the
Aβ sequence by α-secretase (ADAM10/TACE/ADAM17) in the
non-amyloidogenic pathway, thereby abrogating the generation of an intact
Aβ peptide. Alternatively, a small proportion of APP is cleaved in the
amyloidogenic pathway, leading to the secretion of Aβ peptides
(37–42 amino acids) via two proteolytic enzymes, β- and
γ-secretase, known as BACE1 and presenilin, respectively
(1).The proteolytic processing of APP to generate Aβ requires the
trafficking of APP such that APP and BACE1 are brought together in close
proximity for β-secretase cleavage to occur. We and others have shown
that the low density lipoprotein receptor-related protein (LRP), a
multifunctional endocytosis receptor
(2), binds to APP and alters
its trafficking to promote Aβ generation. The loss of LRP substantially
reduces Aβ release, a phenotype that is reversed when full-length
(LRP-FL) or truncated LRP is transfected in LRP-deficient cells
(3,
4). Specifically, LRP-CT
lacking the extracellular ligand binding regions but containing the
transmembrane domain and the cytoplasmic tail is capable of rescuing
amyloidogenic processing of APP and Aβ release in LRP deficient cells
(3). Moreover, the LRP soluble
tail (LRP-ST) lacking the transmembrane domain and only containing the
cytoplasmic tail of LRP is sufficient to enhance Aβ secretion
(5). This activity of LRP-ST is
achieved by promoting APP/BACE1 interaction
(6), although the precise
mechanism is unknown. Although we had hypothesized that one or more
NPXY domains in LRP-ST might underlie the pro-amyloidogenic
processing of APP, we recently found that the 37 C-terminal residues of LRP
(LRP-C37) lacking the NPXY motif was sufficient to robustly promote
Aβ production independent of FE65
(7). Because LRP-C37 likely
acts by recruiting other proteins, we used the LRP-C37 region as bait in a
yeast two-hybrid screen, resulting in the identification of 4 new LRP-binding
proteins (7). Among these, we
focused on Ran-binding protein 9 (RanBP9) in this study, which we found to
play a critical role in the trafficking and processing of APP. RanBP9, also
known as RanBPM, acts as a multi-modular scaffolding protein, bridging
interactions between the cytoplasmic domains of a variety of membrane
receptors and intracellular signaling targets. These include Axl and Sky
(8), MET receptor
protein-tyrosine kinase (9),
and β2-integrin LFA-1
(10). Similarly, RanBP9
interacts with Plexin-A receptors to strongly inhibit axonal outgrowth
(11) and functions to regulate
cell morphology and adhesion
(12,
13). Here we show that RanBP9
robustly promotes BACE1 processing of APP and Aβ generation. 相似文献
7.
8.
Masato Maesako Maiko Uemura Yoshitaka Tashiro Kazuki Sasaki Kiwamu Watanabe Yasuha Noda Karin Ueda Megumi Asada-Utsugi Masakazu Kubota Katsuya Okawa Masafumi Ihara Shun Shimohama Kengo Uemura Ayae Kinoshita 《PloS one》2015,10(9)
Obesity and type 2 diabetes are risk factors of Alzheimer’s disease (AD). We reported that a high fat diet (HFD) promotes amyloid precursor protein (APP) cleavage by β-site APP cleaving enzyme 1 (BACE1) without increasing BACE1 levels in APP transgenic mice. However, the detailed mechanism had remained unclear. Here we demonstrate that HFD promotes BACE1/Adaptor protein-2 (AP-2)/clathrin complex formation by increasing AP-2 levels in APP transgenic mice. In Swedish APP overexpressing Chinese hamster ovary (CHO) cells as well as in SH-SY5Y cells, overexpression of AP-2 promoted the formation of BACE1/AP-2/clathrin complex, increasing the level of the soluble form of APP β (sAPPβ). On the other hand, mutant D495R BACE1, which inhibits formation of this trimeric complex, was shown to decrease the level of sAPPβ. Overexpression of AP-2 promoted the internalization of BACE1 from the cell surface, thus reducing the cell surface BACE1 level. As such, we concluded that HFD may induce the formation of the BACE1/AP-2/clathrin complex, which is followed by its transport of BACE1 from the cell surface to the intracellular compartments. These events might be associated with the enhancement of β-site cleavage of APP in APP transgenic mice. Here we present evidence that HFD, by regulation of subcellular trafficking of BACE1, promotes APP cleavage. 相似文献
9.
Chondroitin Sulfate Accelerates Trans‐Golgi‐to‐Surface Transport of Proteoglycan Amyloid Precursor Protein 下载免费PDF全文
The amyloid precursor protein (APP) is a membrane protein implicated in the pathogenesis of Alzheimer's disease. APP is a part‐time proteoglycan, as splice variants lacking exon 15 are modified by a chondroitin sulfate glycosaminoglycan (GAG) chain. Investigating the effect of the GAG chain on the trafficking of APP in non‐polarized cells, we found it to increase the steady‐state surface‐to‐intracellular distribution, to reduce the rate of endocytosis and to accelerate transport kinetics from the trans‐Golgi network (TGN) to the plasma membrane. Deletion of the cytosolic domain resulted in delayed surface arrival of GAG‐free APP, but did not affect the rapid export kinetics of the proteoglycan form. Protein‐free GAG chains showed the same TGN‐to‐cell surface transport kinetics as proteoglycan APP. Endosome ablation experiments were performed to distinguish between indirect endosomal and direct pathways to the cell surface. Surprisingly, TGN‐to‐cell surface transport of both GAG‐free and proteoglycan APP was found to be indirect via transferrin‐positive endosomes. Our results show that GAGs act as alternative sorting determinants in cellular APP transport that are dominant over cytoplasmic signals and involve distinct sorting mechanisms. 相似文献
10.
Pei Zhi Cheryl Chia Wei Hong Toh Robyn Sharples Isabelle Gasnereau Andrew F. Hill Paul A. Gleeson 《Traffic (Copenhagen, Denmark)》2013,14(9):997-1013
β‐Secretase (BACE1) cleavage of the amyloid precursor protein (APP) represents the initial step in the formation of the Alzheimer's disease associated amyloidogenic Aβ peptide. Substantive evidence indicates that APP processing by BACE1 is dependent on intracellular sorting of this enzyme. Nonetheless, knowledge of the intracellular trafficking pathway of internalised BACE1 remains in doubt. Here we show that cell surface BACE1 is rapidly internalised by the AP2/clathrin dependent pathway in transfected cells and traffics to early endosomes and Rab11‐positive, juxtanuclear recycling endosomes, with very little transported to the TGN as has been previously suggested. Moreover, BACE1 is predominantly localised to the early and recycling endosome compartments in different cell types, including neuronal cells. In contrast, the majority of internalised wild‐type APP traffics to late endosomes/lysosomes. To explore the relevance of the itinerary of BACE1 on APP processing, we generated a BACE1 chimera containing the cytoplasmic tail of TGN38 (BACE/TGN38), which cycles between the cell surface and TGN in an AP2‐dependent manner. Wild‐type BACE1 is less efficient in Aβ production than the BACE/TGN38 chimera, highlighting the relevance of the itinerary of BACE1 on APP processing. Overall the data suggests that internalised BACE1 and APP diverge at early endosomes and that Aβ biogenesis is regulated in part by the recycling itinerary of BACE1. 相似文献
11.
Prabhu Y Burgos PV Schindler C Farías GG Magadán JG Bonifacino JS 《Molecular biology of the cell》2012,23(12):2339-2351
The β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1) is a transmembrane aspartyl protease that catalyzes the proteolytic processing of APP and other plasma membrane protein precursors. BACE1 cycles between the trans-Golgi network (TGN), the plasma membrane, and endosomes by virtue of signals contained within its cytosolic C-terminal domain. One of these signals is the DXXLL-motif sequence DISLL, which controls transport between the TGN and endosomes via interaction with GGA proteins. Here we show that the DISLL sequence is embedded within a longer [DE]XXXL[LI]-motif sequence, DDISLL, which mediates internalization from the plasma membrane by interaction with the clathrin-associated, heterotetrameric adaptor protein 2 (AP-2) complex. Mutation of this signal or knockdown of either AP-2 or clathrin decreases endosomal localization and increases plasma membrane localization of BACE1. Remarkably, internalization-defective BACE1 is able to cleave an APP mutant that itself cannot be delivered to endosomes. The drug brefeldin A reversibly prevents BACE1-catalyzed APP cleavage, ruling out that this reaction occurs in the endoplasmic reticulum (ER) or ER-Golgi intermediate compartment. Taken together, these observations support the notion that BACE1 is capable of cleaving APP in late compartments of the secretory pathway. 相似文献
12.
Bor Luen Tang 《Cell Adhesion & Migration》2009,3(1):118-128
Aberrant and/or cumulative amyloid-beta (Aβ) production, resulting from proteolytic processing of the amyloid precursor protein (APP) by β and γ-secretases, have been postulated to be a main etiological basis of Alzheimer disease (AD). A number of proteins influence the subcellular trafficking itinerary of APP and the β-site APP-cleaving enzyme (BACE1) between the cell surface, endosomes and the trans-Golgi network (TGN). Available evidence suggests that co-residence of APP and BACE1 in the endosomal compartments promotes amyloidogenesis. Retrograde transport of APP out of the endosome to the TGN reduces Aβ production, while APP routed to and kept at the cell surface enhances its non-amyloidogenic, α-secretase-mediated processing. Changes in post-Golgi membrane trafficking in aging neurons that may influence APP processing is particularly relevant to late-onset, idiopathic AD. Dystrophic axons are key features of AD pathology, and impaired axonal transport could play crucial roles in the pathogenesis of idiopathic AD. Recent evidence has also indicated that Aβ-induced synaptic defects and memory impairment could be explained by a loss of both AMPA and NMDA receptors through endocytosis. Detail understanding of factors that influence these neuronal trafficking processes will open up novel therapeutic avenues for preventing or delaying the onset of symptomatic AD.Key words: amyloid precursor protein (APP), β-site APP cleaving enzyme 1 (BACE1), endosome, glutamate receptors, trans-Golgi network (TGN) 相似文献
13.
Saito Y Sano Y Vassar R Gandy S Nakaya T Yamamoto T Suzuki T 《The Journal of biological chemistry》2008,283(51):35763-35771
X11 and X11-like proteins (X11L) are neuronal adaptor proteins whose association to the cytoplasmic domain of amyloid beta-protein precursor (APP) suppresses the generation of amyloid beta-protein (Abeta) implicated in Alzheimer disease pathogenesis. The amyloidogenic, but not amyloidolytic, metabolism of APP was selectively increased in the brain of mutant mice lacking X11L (Sano, Y., Syuzo-Takabatake, A., Nakaya, T., Saito, Y., Tomita, S., Itohara, S., and Suzuki, T. (2006) J. Biol. Chem. 281, 37853-37860). To reveal the actual role of X11 proteins (X11s) in suppressing amyloidogenic cleavage of APP in vivo, we generated X11 and X11L double knock-out mice and analyzed the metabolism of APP. The mutant mice showed enhanced beta-site cleavage of APP along with increased accumulation of Abeta in brain and increased colocalization of APP with beta-site APP-cleaving enzyme (BACE). In the brains of mice deficient in both X11 and X11L, the apparent relative subcellular distributions of both mature APP and its beta-C-terminal fragment were shifted toward the detergent-resistant membrane (DRM) fraction, an organelle in which BACE is active and both X11s are not nearly found. These results indicate that X11s associate primarily with APP molecules that are outside of DRM, that the dissociation of APP-X11/X11L complexes leads to entry of APP into DRM, and that cleavage of uncomplexed APP by BACE within DRM is enhanced by X11s deficiency. Present results lead to an idea that the dysfunction of X11L in the interaction with APP may recruit more APP into DRM and increase the generation of Abeta even if BACE activity did not increase in brain. 相似文献
14.
Yang HC Chai X Mosior M Kohn W Boggs LN Erickson JA McClure DB Yeh WK Zhang L Gonzalez-DeWhitt P Mayer JP Martin JA Hu J Chen SH Bueno AB Little SP McCarthy JR May PC 《Journal of neurochemistry》2004,91(6):1249-1259
Beta-amyloid peptides (Abeta) are produced by a sequential cleavage of amyloid precursor protein (APP) by beta- and gamma-secretases. The lack of Abeta production in beta-APP cleaving enzyme (BACE1)(-/-) mice suggests that BACE1 is the principal beta-secretase in mammalian neurons. Transfection of human APP and BACE1 into neurons derived from wild-type and BACE1(-/-) mice supports cleavage of APP at the canonical beta-secretase site. However, these studies also revealed an alternative BACE1 cleavage site in APP, designated as beta', resulting in Abeta peptides starting at Glu11. The apparent inability of human BACE1 to make this beta'-cleavage in murine APP, and vice versa, led to the hypothesis that this alternative cleavage was species-specific. In contrast, the results from human BACE1 transgenic mice demonstrated that the human BACE1 is able to cleave the endogenous murine APP at the beta'-cleavage site. To address this discrepancy, we designed fluorescent resonance energy transfer peptide substrates containing the beta- and beta'-cleavage sites within human and murine APP to compare: (i) the enzymatic efficiency; (ii) binding kinetics of a BACE1 active site inhibitor LY2039911; and (iii) the pharmacological profiles for human and murine recombinant BACE1. Both BACE1 orthologs were able to cleave APP at the beta- and beta'-sites, although with different efficiencies. Moreover, the inhibitory potency of LY2039911 toward recombinant human and native BACE1 from mouse or guinea pig was indistinguishable. In summary, we have demonstrated, for the first time, that recombinant BACE1 can recognize and cleave APP peptide substrates at the postulated beta'-cleavage site. It does not appear to be a significant species specificity to this cleavage. 相似文献
15.
APLP1 and APLP2, members of the APP family of proteins,behave similarly to APP in that they associate with NMDA receptors and enhance NMDA receptor surface expression 下载免费PDF全文
The function of amyloid precursor protein (APP) is unknown, although the discovery that it contributes to the regulation of surface expression of N‐methyl‐d ‐aspartate (NMDA) receptors has afforded new insights into its functional significance. Since APP is a member of a gene family that contains two other members, amyloid precursor‐like proteins 1 and 2 (APLP1 and APLP2), it is important to determine if the related APP proteins possess the same properties as APP with respect to their interactions with NMDA receptors. Following expression in mammalian cells, both APLP1 and APLP2 behaved similarly to APP in that they both co‐immunoprecipitated with the two major NMDA receptor subtypes, GluN1/GluN2A and GluN1/GluN2B, via interaction with the obligatory GluN1 subunit. Immunoprecipitations from detergent extracts of adult mammalian brain showed co‐immunoprecipitation of APLP1 and APLP2 with GluN2A‐ and GluN2B‐containing NMDA receptors. Furthermore, similarly to APP, APLP1 and APLP2 both enhanced GluN1/GluN2A and GluN1/GluN2B cell surface expression. Thus, all the three members of the APP gene family behave similarly in that they each contribute to the regulation of cell surface NMDA receptor homoeostasis.
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BACE1 (β-site β-amyloid precursor protein (APP)-cleaving enzyme 1) mediates the first proteolytic cleavage of APP, leading to amyloid β-peptide (Aβ) production. It has been reported that BACE1 intracellular trafficking, in particular endosome-to-TGN sorting, is mediated by adaptor complexes, such as retromer and Golgi-localized γ-ear-containing ARF-binding proteins (GGAs). Here we investigated whether sortilin, a Vps10p domain-sorting receptor believed to participate in retromer-mediated transport of select membrane cargoes, contributes to the subcellular trafficking and activity of BACE1. Our initial studies revealed increased levels of sortilin in post-mortem brain tissue of AD patients and that overexpression of sortilin leads to increased BACE1-mediated cleavage of APP in cultured cells. In contrast, RNAi suppression of sortilin results in decreased BACE1-mediated cleavage of APP. We also found that sortilin interacts with BACE1 and that a sortilin construct lacking its cytoplasmic domain, which contains putative retromer sorting motifs, remains bound to BACE1. However, expression of this truncated sortilin redistributes BACE1 from the trans-Golgi network to the endosomes and substantially reduces the retrograde trafficking of BACE1. Site-directed mutagenesis and chimera experiments reveal that the cytoplasmic tail of sortilin, but not those from other VPS10p domain receptors (e.g. SorCs1b and SorLA), plays a unique role in BACE1 trafficking. Our studies suggest a new function for sortilin as a modulator of BACE1 retrograde trafficking and subsequent generation of Aβ. 相似文献
19.
Vetrivel KS Barman A Chen Y Nguyen PD Wagner SL Prabhakar R Thinakaran G 《The Journal of biological chemistry》2011,286(29):26166-26177
Several lines of evidence implicate lipid raft microdomains in Alzheimer disease-associated β-amyloid peptide (Aβ) production. Notably, targeting β-secretase (β-site amyloid precursor protein (APP)-cleaving enzyme 1 (BACE1)) exclusively to lipid rafts by the addition of a glycosylphosphatidylinositol (GPI) anchor to its ectodomain has been reported to elevate Aβ secretion. Paradoxically, Aβ secretion is not reduced by the expression of non-raft resident S-palmitoylation-deficient BACE1 (BACE1-4C/A (C474A/C478A/C482A/C485A)). We addressed this apparent discrepancy in raft microdomain-associated BACE1 processing of APP in this study. As previously reported, we found that expression of BACE1-GPI elevated Aβ secretion as compared with wild-type BACE1 (WTBACE1) or BACE1-4C/A. However, this increase occurred without any difference in the levels of APP ectodomain released following BACE1 cleavage (soluble APPβ), arguing against an overall increase in BACE1 processing of APP per se. Further analysis revealed that WTBACE1 cleaves APP at β- and β'-sites, generating +1 and +11 β-C-terminal fragments and secreting intact as well as N-terminally truncated Aβ. In contrast, three different BACE1-GPI chimeras preferentially cleaved APP at the β-site, mainly generating +1 β-C-terminal fragment and secreting intact Aβ. As a consequence, cells expressing BACE1-GPI secreted relatively higher levels of intact Aβ without an increase in BACE1 processing of APP. Markedly reduced cleavage at β'-site exhibited by BACE1-GPI was cell type-independent and insensitive to subcellular localization of APP or the pathogenic KM/NL mutant. We conclude that the apparent elevation in Aβ secretion by BACE1-GPI is mainly attributed to preferential cleavage at the β-site and failure to detect +11 Aβ species secreted by cells expressing WTBACE1. 相似文献
20.
Glu11 site cleavage and N-terminally truncated A beta production upon BACE overexpression 总被引:6,自引:0,他引:6
Amyloid beta peptides (A beta) are generated by the proteolytic processing of the amyloid beta precursor protein (APP). The newly identified beta-site APP-cleaving enzyme (BACE) cleaves APP at Asp1 as well as between Tyr10 and Glu11 of A beta, producing C-terminal fragments (CTFs) C99 and C89, respectively. Subsequent cleavage by gamma-secretase gives rise to A beta 1-40/42 and A beta 11-40/42. Although both full-length and A beta peptides truncated at residue 11 have been identified in amyloid plaques in the AD brain, the relative proportion of these two cleavage products produced by BACE and secreted into the medium by cultured cells is unknown. Using cell lines stably overexpressing BACE, we found that A beta 11-40 and A beta 11-42 are major A beta cleavage products generated by BACE. We further showed that BACE utilizes both full-length APP as well as C99 as substrates for the production of C89, and that A beta 11-40/42 can be generated by sequential cleavage of single APP molecules by BACE and gamma-secretase. Taken together, the abundance of A beta 11-40/42 produced by BACE suggests that their roles in AD pathogenesis may be underestimated. 相似文献