Protective and Toxic Proteins in Alzheimer’s Disease
Author
Thomsen, Maj Schneider
Term
4. term
Publication year
2012
Submitted on
2012-06-01
Pages
55
Abstract
Baggrund: Når amyloid precursor protein (APP) kløves i hjernen, kan det danne forskellige fragmenter. Én vej giver sAPPα, som har neurobeskyttende egenskaber, mens en anden vej giver sAPPβ og amyloid beta (Aβ), som mistænkes for at være skadeligt ved Alzheimers sygdom. Den eneste forskel mellem sAPPα og sAPPβ er, at sAPPα har 16 ekstra aminosyrer i C-enden. Disse 16 aminosyrer danner også N-enden af Aβ. Det rejste spørgsmålet, om sAPPα kan binde til Aβ. Metode og resultater: Vi brugte en laboratorietest (GST pull-down), hvor GST-mærket sAPPα eller sAPPβ blev fastgjort til glutathion-Sepharose perler, og Aβ1-42 (en 42-aminosyre variant af Aβ) blev tilsat for at teste binding. Ved hjælp af Western blot og kvantitativ måling fandt vi, at Aβ1-42 bandt markant mere til sAPPα end til sAPPβ. Det tyder på, at interaktionen sker via de 16 ekstra aminosyrer i sAPPαs C-ende. For at undersøge dette nærmere lavede vi fem sAPPα-varianter med små ændringer i den 16-aminosyre lange region samt én variant i et andet sekvensmotiv og gentog forsøget. Med undtagelse af én ændring (K612A) reducerede alle varianter bindingen af Aβ1-42 sammenlignet med uændret sAPPα. Det støtter, at C-enden med de 16 aminosyrer er central for bindingen mellem sAPPα og Aβ1-42. Konklusion: sAPPα er tidligere vist at beskytte cellekulturer mod Aβ-induceret toksicitet. Vores fund, at sAPPα binder Aβ, kan være en del af forklaringen på denne neurobeskyttelse, muligvis ved at hjælpe med at opretholde en balance mellem sAPPα og Aβ.
Background: When amyloid precursor protein (APP) is cut in the brain, it can produce different fragments. One route yields sAPPα, which has neuroprotective effects, while another yields sAPPβ and amyloid beta (Aβ), thought to be harmful in Alzheimer’s disease. The only difference between sAPPα and sAPPβ is that sAPPα has 16 extra amino acids at its C-terminus. These same 16 amino acids also form the N-terminus of Aβ. This raised the question of whether sAPPα can bind to Aβ. Methods and results: We used a binding test (GST pull-down) in which GST-tagged sAPPα or sAPPβ was attached to glutathione Sepharose beads and Aβ1-42 (a 42–amino-acid form of Aβ) was added to assess binding. Using Western blotting and densitometry, we found that Aβ1-42 bound much more to sAPPα than to sAPPβ, suggesting that the interaction is mediated by the 16 extra amino acids at the C-terminus of sAPPα. To examine this in more detail, we created five sAPPα variants with small changes in this 16–amino-acid region and one variant in another sequence motif, and repeated the assay. With the exception of one change (K612A), all variants reduced Aβ1-42 binding compared with unmodified sAPPα. These findings support that the C-terminal 16–amino-acid region is critical for binding between sAPPα and Aβ1-42. Conclusion: sAPPα has previously been shown to protect cell cultures from Aβ-induced toxicity. Our finding that sAPPα binds Aβ may help explain this neuroprotection, possibly by helping maintain a balance between sAPPα and Aβ.
[This abstract was generated with the help of AI]
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