Beta amyloid

(Redirected from )
Jump to navigation Jump to search
amyloid beta (A4) precursor protein (peptidase nexin-II, Alzheimer disease)
APP processing.png
Processing of the amyloid precursor protein
Alt. symbolsAD1
Other data
LocusChr. 21 q21.2

WikiDoc Resources for Beta amyloid


Most recent articles on Beta amyloid

Most cited articles on Beta amyloid

Review articles on Beta amyloid

Articles on Beta amyloid in N Eng J Med, Lancet, BMJ


Powerpoint slides on Beta amyloid

Images of Beta amyloid

Photos of Beta amyloid

Podcasts & MP3s on Beta amyloid

Videos on Beta amyloid

Evidence Based Medicine

Cochrane Collaboration on Beta amyloid

Bandolier on Beta amyloid

TRIP on Beta amyloid

Clinical Trials

Ongoing Trials on Beta amyloid at Clinical

Trial results on Beta amyloid

Clinical Trials on Beta amyloid at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Beta amyloid

NICE Guidance on Beta amyloid


FDA on Beta amyloid

CDC on Beta amyloid


Books on Beta amyloid


Beta amyloid in the news

Be alerted to news on Beta amyloid

News trends on Beta amyloid


Blogs on Beta amyloid


Definitions of Beta amyloid

Patient Resources / Community

Patient resources on Beta amyloid

Discussion groups on Beta amyloid

Patient Handouts on Beta amyloid

Directions to Hospitals Treating Beta amyloid

Risk calculators and risk factors for Beta amyloid

Healthcare Provider Resources

Symptoms of Beta amyloid

Causes & Risk Factors for Beta amyloid

Diagnostic studies for Beta amyloid

Treatment of Beta amyloid

Continuing Medical Education (CME)

CME Programs on Beta amyloid


Beta amyloid en Espanol

Beta amyloid en Francais


Beta amyloid in the Marketplace

Patents on Beta amyloid

Experimental / Informatics

List of terms related to Beta amyloid

Amyloid beta (Aβ or Abeta) is a peptide of 39–43 amino acids that appear to be the main constituent of amyloid plaques in the brains of Alzheimer's disease patients. Similar plaques appear in some variants of Lewy body dementia and in inclusion body myositis, a muscle disease. Aβ also forms aggregates coating cerebral blood vessels in cerebral amyloid angiopathy. These plaques are composed of a tangle of regularly ordered fibrillar aggregates called amyloid fibers, a protein fold shared by other peptides such as prions associated with protein misfolding diseases. Research on laboratory rats suggest that the two-molecule, soluble form of the peptide is a causative agent in the development of Alzheimer's and that the two-molecule form is the smallest synaptotoxic species of soluble amyloid beta oligomer [1] [2]


Aβ is formed after sequential cleavage of the amyloid precursor protein, a transmembrane glycoprotein of undetermined function. APP can be processed by α-, β- and γ-secretases; Aβ protein is generated by successive action of the β and γ secretases. The γ secretase, which produces the C-terminal end of the Aβ peptide, cleaves within the transmembrane region of APP and can generate a number of isoforms of 39-43 amino acid residues in length. The most common isoforms are Aβ40 and Aβ42; the shorter form is typically produced by cleavage that occurs in the endoplasmic reticulum, while the longer form is produced by cleavage in the trans-Golgi network.[3] The Aβ40 form is the more common of the two, but Aβ42 is the more fibrillogenic and is thus associated with disease states. Mutations in APP associated with early-onset Alzheimer's have been noted to increase the relative production of Aβ42, and thus one suggested avenue of Alzheimer's therapy involves modulating the activity of β and γ secretases to produce mainly Aβ40.[4]


Autosomal-dominant mutations in APP cause hereditary early-onset Alzheimer's disease, likely as a result of altered proteolytic processing. Increases in either total Aβ levels or the relative concentration of both Aβ40 and Aβ42 (where the former is more concentrated in cerebrovascular plaques and the latter in neuritic plaques)[5] have been implicated in the pathogenesis of both familial and sporadic Alzheimer's disease. Due to its more hydrophobic nature, the Aβ42 is the most amyloidogenic form of the peptide. However the central sequence KLVFFAE is known to form amyloid on its own, and probably forms the core of the fibril.

The "amyloid hypothesis", that the plaques are responsible for the pathology of Alzheimer's disease, is accepted by the majority of researchers but is by no means conclusively established. Intra-cellular deposits of tau protein are also seen in the disease, and may also be implicated. The oligomers that form on the amyloid pathway, rather than the mature fibrils, may be the cytotoxic species.[6]

Intervention strategies

Researchers in Alzheimer's disease have identified five strategies as possible interventions against amyloid:[7]

  • β-Secretase inhibitors. These work to block the first cleavage of APP outside of the cell.
  • γ-Secretase inhibitors (e. g. Semagacestat). These work to block the second cleavage of APP in the cell membrane and would then stop the subsequent formation of Aβ and its toxic fragments.
  • Selective Aβ-42 lowering agents (e. g. Tarenflurbil). These modulate γ-secretase to reduce Aβ-42 production in favor of other (shorter) Aβ versions.
  • Immunotherapies. These stimulate the host immune system to recognize and attack Aβ or provide antibodies that either prevent plaque deposition or enhance clearance of plaques.
  • Anti-aggregation agents. These prevent Aβ fragments from aggregating or clear aggregates once they are formed.[8]

There is some indication that supplementation of the hormone melatonin may be effective against amyloid.[9][10]

Measuring amyloid beta

There are many different ways to measure Amyloid beta. One highly sensitive method is ELISA which is an immuno-sandwich assay which utilizes a pair of antibodies that recognize Amyloid beta.

Imaging compounds, notable Pittsburgh Compound-B, (BTA-1, a thioflavin), can selectively bind to amyloid beta in vitro and in vivo. This technique, combined with PET imaging, has been used to image areas of plaque deposits in Alzheimer's patients.

External links


  1. Scmid, Randolf (2008). "New clue to Alzheimer's found". Yahoo News. Unknown parameter |month= ignored (help)
  2. Shankar GM, Li S, Mehta TH, Garcia-Munoz A, Shepardson NE, Smith I, Brett FM, Farrell MA, Rowan MJ, Lemere CA, Regan CM, Walsh DM, Sabatini BL, Selkoe DJ (2008). "Amyloid-protein dimers isolated directly from Alzheimer's brains impair synaptic plasticity and memory". Nature Medicine (June 22, 2008 online). doi:10.1038/nm1782. PMID 18568035.
  3. Hartmann T, Bieger SC, Brühl B; et al. (1997). "Distinct sites of intracellular production for Alzheimer's disease Aβ40/42 amyloid peptides". Nat. Med. 3 (9): 1016–20. PMID 9288729.
  4. Yin YI, Bassit B, Zhu L, Yang X, Wang C, Li YM (2007). "γ-Secretase Substrate Concentration Modulates the Aβ42/Aβ40 Ratio: Implications for Alzheimer's disease". J. Biol. Chem. 282 (32): 23639–44. doi:10.1074/jbc.M704601200. PMID 17556361.
  5. Lue LF, Kuo YM, Roher AE; et al. (1999). "Soluble amyloid beta peptide concentration as a predictor of synaptic change in Alzheimer's disease". Am. J. Pathol. 155 (3): 853–62. PMC 1866907. PMID 10487842.
  6. Kayed R, Head E, Thompson JL; et al. (2003). "Common structure of soluble amyloid oligomers implies common mechanism of pathogenesis". Science (journal). 300 (5618): 486–9. doi:10.1126/science.1079469. PMID 12702875.
  7. Citron M (2004). "Strategies for disease modification in Alzheimer's disease". Nat. Rev. Neurosci. 5 (9): 677–85. doi:10.1038/nrn1495. PMID 15322526.
  8. Parker, Michael H.; Chen, Robert; Conway, Kelly A.; Lee, Daniel H. S.; Luo, Chi; Boyd, Robert E.; Nortey, Samuel O.; Ross, Tina M.; Scott, Malcolm K.; Reitz, Allen B. (2002). "Synthesis of (+)-5,8-Dihydroxy-3R-methyl-2R-(dipropylamino)-1,2,3,4-tetrahydro-naphthalene: An Inhibitor of β-Amyloid1-42 Aggregation". Bioorg. Med. Chem. 10 (11): 3565–3569. doi:10.1016/S0968-0896(02)00251-1. PMID 12213471.
  9. Lahiri DK, Chen DM, Lahiri P, Bondy S, Greig NH (2005). "Amyloid, cholinesterase, melatonin, and metals and their roles in aging and neurodegenerative diseases". Ann. N. Y. Acad. Sci. 1056: 430–49. doi:10.1196/annals.1352.008. PMID 16387707. Unknown parameter |month= ignored (help)
  10. Wang XC, Zhang YC, Chatterjie N, Grundke-Iqbal I, Iqbal K, Wang JZ (2008). "Effect of melatonin and Melatonylvalpromide on beta-amyloid and neurofilaments in N2a cells". Neurochem. Res. 33 (6): 1138–44. doi:10.1007/s11064-007-9563-y. PMID 18231852. Unknown parameter |month= ignored (help)

Amyloidosis Microchapters


Patient Information


Historical Perspective


Primary amyloidosis
Secondary amyloidosis
Familial amyloidosis
Wild-type (senile) amyloidosis
Cardiac amyloidosis
Beta-2 microglobulin related amyloidosis
Gelsolin related amyloidosis
Lysozyme amyloid related amyloidosis
Leucocyte cell-derived chemotaxin 2 related amyloidosis
Fibrinogen A alpha-chain associated amyloidosis



Differentiating Amyloidosis from other Diseases

Epidemiology and Demographics

Risk Factors


Natural History, Complications and Prognosis


Diagnostic Study of Choice

History and Symptoms

Physical Examination

Laboratory Findings



Echocardiography and Ultrasound

CT scan


Other Imaging Findings

Other Diagnostic Studies


Medical Therapy


Primary Prevention

Secondary Prevention

Cost-Effectiveness of Therapy

Future or Investigational Therapies

Case Studies

Case #1

Beta amyloid On the Web

Most recent articles

Most cited articles

Review articles

CME Programs

Powerpoint slides


American Roentgen Ray Society Images of Beta amyloid

All Images
Echo & Ultrasound
CT Images

Ongoing Trials at Clinical

US National Guidelines Clearinghouse

NICE Guidance

FDA on Beta amyloid

CDC on Beta amyloid

Beta amyloid in the news

Blogs on Beta amyloid

Directions to Hospitals Treating Psoriasis

Risk calculators and risk factors for Beta amyloid

ar:أميلويد بيتا fi:Beta-amyloidi

Template:WH Template:WS