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Molecular mechanism for Alzheimer’s disease : searching for the possible therapeutic targets

Molecular mechanism for Alzheimer’s disease : searching for the possible therapeutic targets. Sungkwon Chung Dept. of Physiology Sungkyunkwan Univ. School of Medicine. Facts on Alzheimer’s disease (AD) It attacks and slowly steals the minds of its victims.

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Molecular mechanism for Alzheimer’s disease : searching for the possible therapeutic targets

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  1. Molecular mechanism for Alzheimer’s disease : searching for the possible therapeutic targets Sungkwon Chung Dept. of Physiology Sungkyunkwan Univ. School of Medicine

  2. Facts on Alzheimer’s disease (AD) • It attacks and slowly steals the minds of its victims. • Symptoms of the disease include: memory loss confusion impaired judgment personality changes disorientation loss of language skills. • Always fatal, Alzheimer's disease is the most common form of irreversible dementia. • 65-74 years : 10%, 75-84: 20%, 85 and older: 50% It is estimated that by 2020, 30 million people will be affected by this devastating disorder worldwide and by 2050, the number could increase to 45 million.

  3. Facts on Alzheimer’s disease (AD) • The average cost for nursing home care is $42,000 per year, and the average lifetime cost of care for an individual with Alzheimer’s is $174,000. Medicare costs for beneficiaries with Alzheimer’s are over$100 billion. • Alzheimer's disease is a progressive, irreversible brain disorder with no known cause or cure. National Institute on Aging Alzheimer's Disease, Causes and Risk Factors “Scientists do not yet fully understand what causes Alzheimer's disease. There probably is not one single cause, • but several factors that affect each person differently.”

  4. Alzheimer’s disease  sporadic (late on-set): > 95% of patients - Epidemiological Factors Hypercholesterolaemia Hypertension Hyperrhomocysteinaemia Diabete mellitus Metabolic syndrome Smoking Systemic inflammation Increased fat intake and obesity  genetic (early on-set): < 5% of patients (FAD) - ApoE ε4 polymorphism - mutations in APP - mutations in presenilin 1, 2 (PS1, PS2)

  5. Amyloid plaques and Neurofibrillary tangles

  6. Amyloid cascade hypothesis

  7. Amyloid Precursor Protein (APP) and its metabolites Citron, Nature Rev. Neurosci., 2004 APP → Aβ Notch1 →NICD p75NTR →p75-ICD

  8. Roberson & Nucke, Science, 2006

  9. Q1: Even though potent inhibitors for γ-secretase had been developed, it could not be used for the patients. Why?

  10. Functional role of presenilin • in Ca2+ regulation

  11. The core of the -secretase complex

  12. Presenilin as negative regulator of capacitative Ca2+ entry (CCE) Yoo et al., 2000

  13. Effect of a CCE inhibitor, SKF, on A42 generation

  14. Presenilin as part of -secretase Leissring et al., J.C.B., 2000 Yoo et al., Neuron, 2000 Presenilin as negative regulator of CCE  CCE pathway may serve as a putative therapeutic target for Alzheimer’s disease.

  15. II. Finding molecular identity of CCE

  16. 0 0.0 -30 -0.3 (pA/pF) -60 -0.6 MIC I wt PS -90 M146L -0.9 L286V ∆E9 -120 0 150 300 450 0 150 300 450 Time (s) -120 MIC -4 -100 * /I of I MAX -3 (pA/pF) (pA/pF) -80 wt PS * I M146L MIC -2 L286V CRAC I -60 ∆E9 I -1 -40 Time (s) 0 L286V wt PS L286V wt PS ∆E9 ∆E9 Down-regulation of IMIC in FAD PS mutants A B C D

  17. Recovery of IMIC from PS mutant cells by PIP2

  18. P P P P P P PI(3,4,5)P3 PI(4,5)P2 PI(4)P PLC IP3 + DAG PI(4,5)P2

  19. Down-regulation of PIP2 in PS mutant cells

  20. Correlation of the level of PIP2 and Aβ42 generation

  21.  TRPM7-like MIC currents underlie the mechanism for PS-mediated modulation of Ca2+ influx. •  The down-regulation of PIP2 levels and the generation of Aβ42 were correlated. •  Up-regulation of PIP2 levels will be a possible therapeutic target Alzheimer’s disease.

  22. III. Ginsenoside: Modulator for -secretase via PIP2

  23. Structure & function of gisenosides

  24. A42-lowering effect of Rg3

  25. A42-lowering effect of ginsenosides

  26. A42-lowering effect of Rg3, Rk1

  27. A42-lowering effect of Rg3 is specific for APP

  28. Increase of PI(4)P by Rg3

  29. Increase of PI(4)P by Rg3 via activation of PI4KII

  30. PI4KII decreases production of A42

  31. A42-lowering effect of Rg3 in vivo

  32. ←PI4KII↑← Rg3

  33. Ab42, sAPPb ELISA assay IV. Activator for -secretase?

  34. MeOH extract (CN1-M) BuOH (B) EtOAc (E) Hexane (H) Dichloromethane (M) HPCL Fractions (E1, E2, E3, E4) E1 HPCL Fractions (1,2,3,4,5,6)

  35. Dose dependent effect of E1-4-4 on A42 and A40 secretion

  36. CN1-M-E1-4-4 increases sAPP, and decreases sAPP

  37. b-secretase or -secretase Cell-free monoclonal antibody

  38. CN1-M-E1-4-4 may directly activates -secretase

  39. Q2: Amyloidogenic Aβ42 is produced by the activity of γ-secretase. However, activators for a-secretase is considered as good therapeutic drug. Why?

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