Anti-APP monoclonal antibody, clone 2C22G4

Alzheimer disease (AD) is characterized by progressive memory loss, reduction in cognitive functions, and damage to the brain. The beta-amyloid precursor protein can be sequentially cleaved by beta-secretase and gamma-secretase. Mutations in the presenilin1(PS1) are the most common cause of Familial Alzheimer's disease (FAD). PS1 mutations can alter the activity of gamma-secretase on the cleavage of the beta-amyloid precursor protein, causing increased A beta production. Previous studies show that the beta APP-C-terminal fragment is first cleaved by beta-scretase, primarily generating long fragments of A beta 48 and A beta 49, followed by the stepwise cleavage of every three amino acid residues at the C terminus, resulting in A beta 48-, 45-, 42 line and A beta 49-, 46-, 43-, 40 line. Here, we used LC-MS/MS to analyze unique peptides IAT, WA, ITL, TVI, IVI through sequential cleavage, combined with ELISA to test the level of A beta 42 and A beta 40 for validation. The results show that most FAD mutant PS1 can alter the level of A beta 42 and A beta 40 monitored by the A beta 42/A beta 40 ratio. Among them, six mutants (1143T, H163P, S170F, Q223R, M233V, and G384A) affect the A beta 42/40 ratio through both A beta 49-40 and A beta 48-38 lines; L166P through decreasing the A beta 49-40 line, six mutants (I143V, M146V, G217A, F280A, L381V, and L392V) through increasing the A beta 48-42 line. More importantly, we found some mutations can affect the gamma-secretase cleavage preference of alpha-CTF and beta-CTF. In conclusion, we found that the FAD PS1 mutations mainly increase the generation of A beta 42 by decreasing the cleavage of A beta 42-A beta 38 and A beta 43-A beta 40.

Several lines of neuroimmunological evidence correlate the development of the inflammatory responses of the brain with the formation of amyloid plaques associated with the pathogenesis of neurodegenerative disorders such as Alzheimer's disease. Within this context, we tested the ability of interleukin-1 beta (IL-1 beta) to regulate the processing of beta-amyloid precursor protein (beta-APP) in neuroglioma U251 cells. Our findings have shown that short-term treatment with IL-1 beta (2 hr) resulted in a concentration-dependent decrease in the amount of the cell-associated form of beta-APP in U251 cells as compared to untreated cells, whereas a 2-hr treatment with IL-1 beta led to increased release of secreted APP alpha fragment (sAPP alpha) into the conditioned media of the cells. The fact that sAPP alpha is an alpha-secretase cleavage metabolite of the cell-associated form of beta-APP, and the observation that IL-1 beta-induced sAPP alpha release could be blocked by tissue inhibitors of metalloproteinases-1 (alpha-secretase inhibitors), suggested that alpha-secretase might be involved in IL-1 beta-incluced-sAPP alpha release. Moreover, to determine whether an intracellular signaling pathway mediates the IL-1 beta-induced increase in sAPP alpha secretion, we used various specific signaling inhibitors and found that sAPP alpha release is significantly blocked by the mitogen-activated protein kinase (MEK1/2) inhibitor PD98059 and the c-Jun N-terminal kinase inhibitor SP600125. These findings suggested that the mechanism of IL-1 beta-induced-sAPP alpha release is dependent on MEK1/2- and JNK-activated alpha-secretase cleavage in neuroglioma U251 cells. (c) 2005 Wiley-Liss, Inc.