Alzheimer's Disease Research: Detecting and Analyzing Alzheimer's Disease Targets
Amyloid Beta, BACE1, Amyloid Precursor Protein (APP), and more
Alzheimer’s Disease (AD) is a neurodegenerative disease with a complex etiology. AD is marked by amyloid-beta (Ab) peptide deposits in the cerebral cortex, which are typically referred to as plaques; these plaque deposits are initially composed of Ab peptide that spans 40 amino acids (Ab40; 1). Later in the disease’s progression, the slightly longer and more hydrophobic form, Ab42, accumulates in cells. Ab42 is highly prone to self-aggregation. Another species of Ab remains soluble and is thought to “seed” brain matter for eventual plaque formation (2). While much is known about the characteristics and deposition patterns of Ab plaques in the brain, far less is realized about the actual in vivo triggers that lead to these plaques and their deposition.
The different Ab peptides are produced by the proteolytic cleavage of amyloid precursor protein (APP), a process that is largely mediated by the enzymes beta- and gamma-secretase. Beta secretase, or BACE1, is a transmembrane protein that contains two aspartate residues in its active site. Gamma-secretase is also a transmembrane protein that, as part of a larger complex including Presenilin-1, cleaves APP. The cleavage of APP by both the beta- and gamma-secretases via the amyloidogenic pathway results in a number of Ab peptides that range from 36 to 43 amino acids in length.
As Ab self-aggregates into oligomers and forms plaques, it is accompanied by neurofibrillary tangles (NFT) containing hyperphosphorylated microtubule-associated protein tau (MAPT). The hyperphosphorylation of tau disrupts its normal role in aiding axonal transport and may be one of the neurotoxic effects of Ab (3). Furthermore, Ab disrupts the normal clearance of hyperphosphorylated tau by the proteasome, accelerating the accumulation of NFTs and toxic species of soluble tau. See examples of use from the peer-reviewed literature.
We offer several ELISA kits and antibodies1 that can be used to analyze AD targets by Western blot or immunohistochemistry2. A selection of these reagents is shown in the table below:
|Amyloid Beta||10027A (12B2), 18584A (N), 10323A and 10326A (82E1), 10379A (11A1)||IHC, WB, IP, depending on clone||Antibody series includes products for Amyloid beta: (11-28), (N), (N) (821E), and E22P (11A1).|
|27729A, 27725A||ELISA||Quantify human Amyloid Beta (1-x) and human Amyloid Beta Oligomers (82E1 specific) in serum, plasma, CSF, brain tissue extract, or cell culture media.|
|BACE1||28051A (42), 18711A (C)||IHC, WB, IP, depending on clone||Antibody series includes products for BACE1 (42) and (C).|
|27752A||ELISA||Quantify conserved BACE1 in cell lysate or brain tissue extract.|
|Alpha2, 6-Sialyltransferase||18983A, 18985A, 28047A||WB||Antibody series includes products for alpha2, 6-Sialyltransferase C,(E41), M2, and E41).|
|27408A, 27762A||ELISA||Quantify Alpha2, 6-Sialyltransferase in serum, plasma, or cell culture media.|
|ApoE||18171A (A299), 10025A (5B5)||WB, IHC||Antibody series includes products for ApoE (A299) and Apo E4 (5B5).|
|Amyloid Precursor Protein (APP)||28053A (18), 28055A (597), 18961A (C), 11090A (clone 10D1), 28021A, 28133A (351)||IHC, WB, IP, depending on clone||Antibody series includes products for APP (18), APP (597), APP (C), APP (N) (10D1), APP (Phosphorylated), and APP770 (351).|
|27736A||ELISA||Quantify human APP770 in plasma, CSF or cell culture media.|
|Soluble APP (α and ß)||11088A (2B3), 10321A (6A1), 18957A (wt)||IHC, WB, IP, depending on clone||Antibody series includes products for sAPP alpha (2B3), sAPP beta-Swedish Type (6A1), and sAPP beta-Wild Type.|
|27776A, 27734A, 27732A, 27731A||ELISA||Quantify human APP betaCTF in cell lysate; human sAPP alpha in plasma, CSF, serum or cell culture media; human sAPP beta-w in plasma, CSF, or cell culture media; and human sAPP, Total in plasma, CSF, serum or cell culture media.|
|Drebrin A||28023A||IHC, IP, WB||Antibody recognizes Drebrin A (DAS2).|
|Tau||18721A, 11092A (phosphorylated), 10233A (9A1), 10235A (1A1), 10237A (2B11)||WB, IHC||Antibody series includes products for Tau, Tau phosphorylated (C5), Tau/Amino Junction (9A1), Tau/E2 Junction (1A1), Tau/Repeat Domain (2B11).|
1 Offered in partnership with IBL Co., Ltd., Japan. References listed below cite IBL or Immuno-Biological Laboratories as the kit manufacturer.
2 WB, Western Blot; IHC, Immunohistochemistry; ELISA, Enzyme-linked Immunosorbent Assay
The studies cited below used IBL brand antibodies for ELISA or immunostaining procedures. The following areas were investigated:
Sontag, E. et al. (2007) Protein Phosphatase 2A Methyltransferase Links Homocysteine Metabolism with Tau and Amyloid Precursor Protein Regulation. J. Neurosci. 27(11):2751–2759.
Phosphorylated amyloid beta and tau peptides are associated with AD. Homocysteine may be linked to AD risk because it increases SAH levels, inhibiting methyltransferase-dependent reactions. Neuroblastoma cells incubated with SAH showed reduced methylation of protein phosphatase 2A (PP2A), which leads to reduced substrate specificity and accumulation of both phosphorylated tau and APP isoforms as well as an increase in beta secretase-cleaved APP fragments and amyloid beta peptides. SAH and SAM-treated Neuro-2a cells were lysed and used in Western blot analysis; blots were probed with anti-APP beta antibody.
Matsuda, S. et al. (2008) BRI2 Inhibits Amyloid β-Peptide Precursor Protein Processing by Interfering with the Docking of Secretases to the Substrate. J. Neurosci. 28(35):8668–8676.
Two familial Alzheimer’s disease cases were studied regarding their aberrant Ab precursor protein processing. The protein BRI2 inhibits APP processing by interfering with g-secretase docking onto APP and subsequent cleavage by alpha and beta-secretases. Both the British and Danish AD-like familial dementias carry BRI2 mutations. ELISA on sAPPalpha and sAPPbeta levels were measured via ELISA using APP antibodies on HEK293APP cells transfected with shRNA corresponding to human BRI2 (sh5 and sh10) or a point mutant of sh5 (m1); sAPPalpha and sAPPbeta levels were increased when BRI2 was inhibited by the shRNAs but not by the non-functional point mutant sh5. Also, sAPPalpha and sAPPbeta levels of Bri2-/- mice were found higher when measured by ELISA.
Kitazume, S. et al. (2005) In Vivo Cleavage of α2,6-Sialyltransferase by Alzheimer β-Secretase. J. Biol. Chem. 280(9):8589–8595.
BACE1 is best known for cleaving amyloid precursor protein (APP), but it also acts on another substrate, beta-galactoside alpha 2,6-sialyltransferase (ST6Gal I). ST6Gal I KO mice express only one-third plasma ST6Gal I as WT mice; conversely, BACE1 transgenic mice have significantly increased levels of plasma ST6Gal I. In order to study BACEI in vivo activity, ST6Gal I (E41) antibody was used to conduct Western blots of Long-Evans Cinnamon (LEC) rat plasma samples.
Murakami, K et al. (2011) SOD1 (Copper/Zinc Superoxide Dismutase) Deficiency Drives Amyloid β Protein Oligomerization and Memory Loss in Mouse Model of Alzheimer Disease. J. Biol. Chem. 286(52)44557–44568.
An AD mouse model deficient in superoxide dismutase 1 (SOD1) was found to have accelerated Ab oligomerization and memory impairment compared with a control AD mouse model. Western blot was performed using anti-Ab antibody (6E10), and the oligomer Ab kit was used.
Lauritzen, I. et al. (2012) The β-Secretase-Derived C-Terminal Fragment of βAPP, C99, But Not Aβ, Is a Key Contributor to Early Intraneuronal Lesions in Triple-Transgenic Mouse Hippocampus. J. Neurosci. 32(46):16243–16255.
Triple-transgenic mice containing mutations for the betaAPP, tau and presenilin genes were examined for site accumulation of the beta-secretase derived beta APP fragment C99 as a function of age. Immunohistochemistry of mouse brain hippocampal sections using a 1:100 dilution of the human amyloid beta (1-16) antibody revealed that C99 is one of the earliest betaAPP catabolites and a major contributor to intracellular betaAPP related immunoreactivity in triple transgenic mice. These data suggest that it is an initiator of the AD process.
Park, K. et al. (2007) Conditional Neuronal Simian Virus 40 T Antigen Expression Induces Alzheimer-Like Tau and Amyloid Pathology in Mice. J. Neurosci. 27(11):2969–2978.
Simian virus 40 large T antigen (TAg) using the Tet-Off system driven by the CaM kinase II promoter was used to induce cell cycle reentry in mouse brain neurons and result in neurofibrillary tangle-like generation and amyloid deposits akin to the Alzheimer’s Disease profile. TAg mouse brain slices were then immunoblotted at a concentration of 1:500 with APP/Abeta (82E1) antibody.
- Selkoe, D.J. (2001) Physiol. Rev. 81(2):741–766.
- Langer, F. et al. J. Neurosci. (2011)31(41):14488–14495.
- Jin, M. et al. (2011) PNAS 108(14):5819–5824.