scholarly journals Contribution of the endosomal-lysosomal and proteasomal systems in Amyloid-β Precursor Protein derived fragments processing

2018 ◽  
Author(s):  
Caroline Evrard ◽  
Pascal Kienlen-Campard ◽  
Rémi Opsomer ◽  
Bernadette Tasiaux ◽  
Jean-Noël Octave ◽  
...  
Keyword(s):  
Amyloid Β ◽  
Full Length ◽  
Precursor Protein ◽  
Degradation Pathways ◽  
Aβ Peptides ◽  
Hek 293 ◽  
App Processing ◽  
Amyloid Deposits ◽  
App Metabolism ◽  
Carboxy Terminal

AbstractAβ peptides, the major components of amyloid deposits of Alzheimer’s disease, are released following sequential cleavages by secretases of its precursor named the amyloid precursor protein (APP). In addition to secretases, degradation pathways, in particular the endosomal/lysosomal and proteasomal systems have also been reported to contribute to APP processing. However, the respective role of each of these pathways towards APP metabolism remains to be established. To address this, we used HEK 293 cells and primary neurons expressing full-length APPWT or the β-secretase-derived C99 fragments (β-CTFs) in which degradation pathways were selectively blocked using pharmacological drugs. APP metabolites, including carboxy-terminal fragments (CTFs), soluble APP (sAPP) and Aβ peptides were studied. In this report, we show that APP-CTFs produced from endogenous or overexpressed full-length APP are mainly processed by γ-secretase and the endosomal/lysosomal pathway, while in sharp contrast, overexpressed C99 alone is mainly degraded by the proteasome and to a lesser extent by γ-secretase.

The Absence of Myelin Basic Protein Reduces Non-Amyloidogenic Processing of Amyloid Precursor Protein

2021 ◽  
Vol 18 ◽  
Author(s):  
Chika Seiwa ◽  
Ichiro Sugiyama ◽  
Makoto Sugawa ◽  
Hiroaki Murase ◽  
Chiaki Kudoh ◽  
...  
Keyword(s):  
Amyloid Precursor Protein ◽  
Myelin Basic Protein ◽  
Basic Protein ◽  
Amyloid Β ◽  
Precursor Protein ◽  
Amyloid Β Protein ◽  
Pathological Feature ◽  
Novel Therapy ◽  
App Processing ◽  
App Metabolism

Background: The accumulation of amyloid β-protein (Aβ) in the brain is a pathological feature of Alzheimer’s disease (AD). Aβ peptides originate from amyloid precursor protein (APP). APP can be proteolytically cleaved through amyloidogenic or non-amyloidogenic pathways. The molecular effects on APP metabolism / processing may be influenced by myelin and the breakdown of myelin basic protein (MBP) in AD patients and mouse models of AD pathology. Methods: We directly tested whether MBP can alter influence APP processing in MBP-/- mice, known as Shiverer (shi/shi) mice, in which no functional MBP is produced due to gene breakage from the middle of MBP exon II. Results: A significant reduction of the cerebral sAPPα level in Shiverer (shi/shi) mice was found, although the levels of both total APP and sAPPβ remain unchanged. The reduction of sAPPα was considered to be due to the changes in the expression levels of a disintegrin and metalloproteinase-9 (ADAM9) catalysis and non-amyloid genic processing of APP in the absence of MBP because it binds to ADAM9. MBP -/- mice exhibited increased Aβ oligomer production. Conclusion: Together, these findings suggest that in the absence of MBP, there is a marked reduction of non-amyloidogenic APP processing to sAPPα, and targeting myelin of oligodendrocytes may be a novel therapy for the prevention and treatment of AD.

scholarly journals The cellular expression and proteolytic processing of the amyloid precursor protein is independent of TDP-43

2020 ◽  
Vol 40 (4) ◽  
Author(s):  
David A. Hicks ◽  
Alys C. Jones ◽  
Stuart M. Pickering-Brown ◽  
Nigel M. Hooper
Keyword(s):  
Amyloid Precursor Protein ◽  
Amyloid Β ◽  
Proteolytic Processing ◽  
Precursor Protein ◽  
Aβ Peptides ◽  
App Processing ◽  
Cellular Expression ◽  
Aβ Generation ◽  
Human Neuronal Cells ◽  
Inducible Cell Line

Abstract Alzheimer’s disease (AD) is a neurodegenerative condition, of which one of the cardinal pathological hallmarks is the extracellular accumulation of amyloid β (Aβ) peptides. These peptides are generated via proteolysis of the amyloid precursor protein (APP), in a manner dependent on the β-secretase, BACE1 and the multicomponent γ-secretase complex. Recent data also suggest a contributory role in AD of transactive response DNA binding protein 43 (TDP-43). There is little insight into a possible mechanism linking TDP-43 and APP processing. To this end, we used cultured human neuronal cells to investigate the ability of TDP-43 to interact with APP and modulate its proteolytic processing. Immunocytochemistry showed TDP-43 to be spatially segregated from both the extranuclear APP holoprotein and its nuclear C-terminal fragment. The latter (APP intracellular domain) was shown to predominantly localise to nucleoli, from which TDP-43 was excluded. Furthermore, neither overexpression of each of the APP isoforms nor siRNA-mediated knockdown of APP had any effect on TDP-43 expression. Doxycycline-stimulated overexpression of TDP-43 was explored in an inducible cell line. Overexpression of TDP-43 had no effect on expression of the APP holoprotein, nor any of the key proteins involved in its proteolysis. Furthermore, increased TDP-43 expression had no effect on BACE1 enzymatic activity or immunoreactivity of Aβ1-40, Aβ1-42 or the Aβ1-40:Aβ1-42 ratio. Also, siRNA-mediated knockdown of TDP-43 had no effect on BACE1 immunoreactivity. Taken together, these data indicate that TDP-43 function and/or dysfunction in AD is likely independent from dysregulation of APP expression and proteolytic processing and Aβ generation.

scholarly journals Distinct anterograde trafficking pathways of BACE1 and amyloid precursor protein from the TGN and the regulation of amyloid-β production

2020 ◽  
Vol 31 (1) ◽  
pp. 27-44 ◽  
Author(s):  
Jing Zhi A. Tan ◽  
Lou Fourriere ◽  
Jingqi Wang ◽  
Franck Perez ◽  
Gaelle Boncompain ◽  
...  
Keyword(s):  
Amyloid Precursor Protein ◽  
Secretory Pathway ◽  
Amyloid Β ◽  
Precursor Protein ◽  
Primary Neurons ◽  
App Processing

The anterograde trafficking of BACE1 and the potential processing of amyloid precursor protein along the secretory pathway remain poorly defined. Our findings reveal that Golgi exit of BACE1 and APP in primary neurons is tightly regulated, resulting in their segregation along different transport routes, which limits APP processing.

scholarly journals A cellular complex of BACE1 and γ-secretase sequentially generates Aβ from its full-length precursor

2019 ◽  
Vol 218 (2) ◽  
pp. 644-663 ◽  
Author(s):  
Lei Liu ◽  
Li Ding ◽  
Matteo Rovere ◽  
Michael S. Wolfe ◽  
Dennis J. Selkoe
Keyword(s):  
Molecular Weight ◽  
Cultured Cells ◽  
Amyloid Β ◽  
Full Length ◽  
Aβ Peptides ◽  
Whole Cells ◽  
Sequential Processing ◽  
Catalytically Active ◽  
Cellular Complex

Intramembrane proteolysis of transmembrane substrates by the presenilin–γ-secretase complex is preceded and regulated by shedding of the substrate’s ectodomain by α- or β-secretase. We asked whether β- and γ-secretases interact to mediate efficient sequential processing of APP, generating the amyloid β (Aβ) peptides that initiate Alzheimer’s disease. We describe a hitherto unrecognized multiprotease complex containing active β- and γ-secretases. BACE1 coimmunoprecipitated and cofractionated with γ-secretase in cultured cells and in mouse and human brain. An endogenous high molecular weight (HMW) complex (∼5 MD) containing β- and γ-secretases and holo-APP was catalytically active in vitro and generated a full array of Aβ peptides, with physiological Aβ42/40 ratios. The isolated complex responded properly to γ-secretase modulators. Alzheimer’s-causing mutations in presenilin altered the Aβ42/40 peptide ratio generated by the HMW β/γ-secretase complex indistinguishably from that observed in whole cells. Thus, Aβ is generated from holo-APP by a BACE1–γ-secretase complex that provides sequential, efficient RIP processing of full-length substrates to final products.

scholarly journals Enhancing α-secretase Processing for Alzheimer’s Disease—A View on SFRP1

2020 ◽  
Vol 10 (2) ◽  
pp. 122 ◽  
Author(s):  
Bor Luen Tang
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Amyloid Β ◽  
Experimental Therapeutics ◽  
Related Protein ◽  
Endogenous Inhibitor ◽  
Aβ Peptides ◽  
App Processing ◽  
Promising Therapeutic Target ◽  
A Disintegrin And Metalloproteinase

Amyloid β (Aβ) peptides generated via sequential β- and γ-secretase processing of the amyloid precursor protein (APP) are major etiopathological agents of Alzheimer’s disease (AD). However, an initial APP cleavage by an α-secretase, such as the a disintegrin and metalloproteinase domain-containing protein ADAM10, precludes β-secretase cleavage and leads to APP processing that does not produce Aβ. The latter appears to underlie the disease symptom-attenuating effects of a multitude of experimental therapeutics in AD animal models. Recent work has indicated that an endogenous inhibitor of ADAM10, secreted-frizzled-related protein 1 (SFRP1), is elevated in human AD brains and associated with amyloid plaques in mouse AD models. Importantly, genetic or functional attenuation of SFRP1 lowered Aβ accumulation and improved AD-related histopathological and neurological traits. Given SFRP1′s well-known activity in attenuating Wnt signaling, which is also commonly impaired in AD, SFRP1 appears to be a promising therapeutic target for AD. This idea, however, needs to be addressed with care because of cancer enhancement potentials resulting from a systemic loss of SFRP1 activity, as well as an upregulation of ADAM10 activity. In this focused review, I shall discuss α-secretase-effected APP processing in AD with a focus on SFRP1, and explore the contrasting perspectives arising from the recent findings.

Cerebrospinal fluid biomarkers of β-amyloid metabolism in multiple sclerosis

2012 ◽  
Vol 19 (5) ◽  
pp. 543-552 ◽  
Author(s):  
Kristin Augutis ◽  
Markus Axelsson ◽  
Erik Portelius ◽  
Gunnar Brinkmalm ◽  
Ulf Andreasson ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Cerebrospinal Fluid ◽  
Inflammatory Diseases ◽  
Amyloid Β ◽  
Csf Biomarkers ◽  
Aβ Peptide ◽  
Aβ Peptides ◽  
App Metabolism ◽  
Disease Modifying

Background: Amyloid precursor protein (APP) and amyloid β (Aβ) peptides are intensely studied in neuroscience and their cerebrospinal fluid (CSF) measurements may be used to track the metabolic pathways of APP in vivo. Reduced CSF levels of Aβ and soluble APP (sAPP) fragments are reported in inflammatory diseases, including multiple sclerosis (MS); but in MS, the precise pathway of APP metabolism and whether it can be affected by disease-modifying treatments remains unclear. Objective: To characterize the CSF biomarkers of APP degradation in MS, including the effects of disease-modifying therapy. Methods: CSF samples from 87 MS patients (54 relapsing–remitting (RR) MS; 33 secondary progressive (SP) MS and 28 controls were analyzed for sAPP and Aβ peptides by immunoassays, plus a subset of samples was analyzed by immunoprecipitation and mass spectrometry (IP-MS). Patients treated with natalizumab or mitoxantrone were examined at baseline, and after 1–2 years of treatment. Results: CSF sAPP and Aβ peptide levels were reduced in MS patients; but they increased again towards normal, after natalizumab treatment. A multivariate model of IP-MS-measured Aβ species separated the SPMS patients from controls, with RRMS patients having intermediate levels. Conclusions: We confirmed and extended our previous observations of altered CSF sAPP and Aβ peptide levels in MS patients. We found that natalizumab therapy may be able to counteract the altered APP metabolism in MS. The CSF Aβ isoform distribution was found to be distinct in SPMS patients, as compared to the controls.

scholarly journals The Golgi-Localized γ-Ear-Containing ARF-Binding (GGA) Proteins Alter Amyloid-β Precursor Protein (APP) Processing through Interaction of Their GAE Domain with the Beta-Site APP Cleaving Enzyme 1 (BACE1)

PLoS ONE ◽  
2015 ◽  
Vol 10 (6) ◽  
pp. e0129047 ◽  
Author(s):  
Bjoern von Einem ◽  
Anke Wahler ◽  
Tobias Schips ◽  
Alberto Serrano-Pozo ◽  
Christian Proepper ◽  
...  
Keyword(s):  
Amyloid Β ◽  
Precursor Protein ◽  
App Processing

scholarly journals A novel mechanism for the regulation of amyloid precursor protein metabolism

2002 ◽  
Vol 158 (1) ◽  
pp. 79-89 ◽  
Author(s):  
Qi Chen ◽  
Hideo Kimura ◽  
David Schubert
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cell Adhesion ◽  
Amyloid Precursor Protein ◽  
Proteasome Inhibitors ◽  
Amyloid Β ◽  
Cellular Adhesion ◽  
Precursor Protein ◽  
Amyloid Β Peptide ◽  
App Processing

Modifier of cell adhesion protein (MOCA; previously called presenilin [PS] binding protein) is a DOCK180-related molecule, which interacts with PS1 and PS2, is localized to brain areas involved in Alzheimer's disease (AD) pathology, and is lost from the soluble fraction of sporadic Alzheimer's disease (AD) brains. Because PS1 has been associated with γ-secretase activity, MOCA may be involved in the regulation of β-amyloid precursor protein (APP) processing. Here we show that the expression of MOCA decreases both APP and amyloid β-peptide secretion and lowers the rate of cell-substratum adhesion. In contrast, MOCA does not lower the secretion of amyloid precursor-like protein (APLP) or several additional type 1 membrane proteins. The phenotypic changes caused by MOCA are due to an acceleration in the rate of intracellular APP degradation. The effect of MOCA expression on the secretion of APP and cellular adhesion is reversed by proteasome inhibitors, suggesting that MOCA directs nascent APP to proteasomes for destruction. It is concluded that MOCA plays a major role in APP metabolism and that the effect of MOCA on APP secretion and cell adhesion is a downstream consequence of MOCA-directed APP catabolism. This is a new mechanism by which the expression of APP is regulated.

scholarly journals Full-length amyloid precursor protein regulates lipoprotein metabolism and amyloid-β clearance in human astrocytes

2018 ◽  
Vol 293 (29) ◽  
pp. 11341-11357 ◽  
Author(s):  
Lauren K. Fong ◽  
Max M. Yang ◽  
Rodrigo dos Santos Chaves ◽  
Sol M. Reyna ◽  
Vanessa F. Langness ◽  
...  
Keyword(s):  
Amyloid Precursor Protein ◽  
Lipoprotein Metabolism ◽  
Amyloid Β ◽  
Full Length ◽  
Precursor Protein ◽  
Human Astrocytes

Using Small Peptide Segments of Amyloid-β and Humanin to Examine their Physical Interactions

2019 ◽  
Vol 26 (7) ◽  
pp. 502-511 ◽  
Author(s):  
Deborah L. Heyl ◽  
Brandon Iwaniec ◽  
Daniel Esckilsen ◽  
Deanna Price ◽  
Prathyusha Guttikonda ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amyloid Fibrils ◽  
Amyloid Β ◽  
Full Length ◽  
Binding Kinetics ◽  
Amino Acid Residues ◽  
Aβ Peptides ◽  
Physical Interactions ◽  
Peptide Segments ◽  
Kinetics Of

Background: Amyloid fibrils in Alzheimer’s disease are composed of amyloid-β (Aβ) peptides of variant lengths. Humanin (HN), a 24 amino acid residue neuroprotective peptide, is known to interact with the predominant Aβ isoform in the brain, Aβ (1-40). Methods: Here, we constructed smaller segments of Aβ and HN and identified residues in HN important for both HN-HN and HN-Aβ interactions. Peptides corresponding to amino acid residues 5- 15 of HN, HN (5-15), HN (5-15, L11S), where Leu11 was replaced with Ser, and residues 17-28 of Aβ, Aβ (17-28), were synthesized and tested for their ability to block formation of the complex between HN and Aβ (1-40). Results: Co-immunoprecipitation and binding kinetics showed that HN (5-15) was more efficient at blocking the complex between HN and Aβ (1-40) than either HN (5-15, L11S) or Aβ (17-28). Binding kinetics of these smaller peptides with either full-length HN or Aβ (1-40) showed that HN (5- 15) was able to bind either Aβ (1-40) or HN more efficiently than HN (5-15, L11S) or Aβ (17-28). Compared to full-length HN, however, HN (5-15) bound Aβ (1-40) with a weaker affinity suggesting that while HN (5-15) binds Aβ, other residues in the full length HN peptide are necessary for maximum interactions. Conclusion: L11 was more important for interactions with Aβ (1-40) than with HN. Aβ (17-28) was relatively ineffective at binding to either Aβ (1-40) or HN. Moreover, HN, and the smaller HN (5-15), HN (5-15 L11S), and Aβ (17-28) peptides, had different effects on regulating Aβ (1-40) aggregation kinetics.

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