Protein misfolding diseases(Alzheimer’s)

Zeinab Mokhtari

Introduction

Alzheimer’s disease

Monday, July-5-2010

Protein misfolding diseases

Preventing amyloid aggregate formation

References

In the name of

God

2

Protein folding

Protein folding refers to the process by which a protein assumes its characteristic structure, known as the native state. The most fundamental question of how an aminoacid sequence specifies both a native structure and the pathway to attain that state has defined the protein folding field.

3

the first phaseUnderstanding the mechanisms of protein folding and uncovering the fundamental principles that govern the folding transition

the second phaseWhat are the mechanisms of protein folding in a context, such as under the influence of other biological molecules in the cellular environment?

Fig. 1. Growth of the Protein Folding Field.The average number ofpublications per year in protein folding field and the average number of publications per year that are dedicated to application

Protein folding

two predominant phases

4

Studying protein folding

Anfinsen

• showing that proteins can fold spontaneously• in vitro studies• a milliseconds-to-seconds time scale

Levinthal

o a random conformation search does not occur in foldingo proteins fold by specific ‘folding pathways’o well-defined partially-structured intermediate states

A small number of residues (folding nucleus) need to form their native contacts in order for the folding reaction to proceed fast into the native state.nucleation theory

Protein folding

5

Protein engineering, nuclear magnetic resonance (NMR), mass spectrometry, hydrogen exchange, fluorescence resonance energy transfer (FRET), and atomic force microscopy (AFM)

Computational methods

The Fold-Rate server (http://psfs.cbrc.jp/fold-rate/)The Parasol folding server (http://parasol.tamu.edu/groups/amatogroup/foldingserver)…

The close interplay of computational and experimental efforts has advanced our knowledge of protein folding kinetics, including predicting the protein folding rate, identifying the kinetically-important residues, and characterizing the multiple pathways.

Experimental methods

Protein folding

Studying protein folding

6

I. protein folding in vivo is usually assisted by molecular machinery, such as chaperones (in an ATP-dependent manner), and often involves small molecule cofactors.

II. the concentrations of macromolecular solutes in cells can reach hundreds of grams per liter , but most in vitro studies are performed in buffered solution with <1% of the cellular macromolecule concentration.

Two major differences between protein folding in vivo and in vitro :

Protein folding

7

The thermodynamic stability of a protein is measured by the free-energy difference between the folded state and the unfolded state:

∆G = Gunfold-Gfold

Experimentally, ∆G values can be obtained from denaturing experiments where the protein unfolds by increasing temperature or by adding denaturing agents such as urea and guanidinium HCl (GdHCl).

Native State, one conformation

Unfolded, many conformations

Protein folding

8

While all the information needed for proteins to fold is encoded in their amino-acid sequence, there are many more elements that play a part in vivo. In a crowded cellular environment, surrounded by interacting proteins, nascent polypeptides face a formidable challenge in finding the correct interactions that result in a folded and functional protein.

Protein folding

9

Molecular chaperones, recognize misfolded proteins and provide an environment conducive to the formation of the appropriate native contacts.

Protein folding

Protein misfolding diseases(Alzheimer’s)

Introduction

Alzheimer’s disease

Protein misfolding diseases

Preventing amyloid aggregate formation

References ZeinabMokhtariMonday, J uly-5-2010

11

Many diseases are now associated with protein aggregation and particularly with a form of ordered aggregate called the amyloid fibrils.

Protein misfolding

12

Protein folding diseases:

excessive quantities of wrongly folded proteins collect in the form of uncontrolled piles of molecular rubbish (amyloidoses).

a small error in the genetic blueprint leads to incomplete folding of a protein, which affects its function.

(P53 : the malfunctioning of central tumour suppressor could cause cancer. )

13

DiseasePick’sAlzheimer’sParkinson’sPrion disease (e.g. Mad Cow) Amyloid Lateral Sclerosis ( Lou Gehrig’s)Huntington’s Disease

ProteintauAPPalpha synucleinprion proteinTDP-43

Huntingtin

Protein misfolding diseases

Protein misfolding

amyloidoses

Protein misfolding diseases(Alzheimer’s)

Zeinab Mokhtari

Introduction

Alzheimer’s disease

Monday, July-5-2010

Protein misfolding diseases

Preventing amyloid aggregate formation

References

15

Alois Alzheimer and family,1910

Auguste D

Alzheimer

16

Alzheimer

17

Alzheimer’s is a progressive disease. Age is the biggest risk factor. We don’t know what causes it. We can temporarily slow it’s progression. We can’t cure it. Caregivers and support groups are very important. There is always hope for the future.

Alzheimer

Normal AD

No one knows what causes AD to begin, but we do know a lot about what happens in the brain once AD takes hold.

18

1 .Recent memory loss affecting job 2 .Difficulty performing familiar tasks

3 .Problems with language 4 .Disorientation to time or place

5 .Poor or decreased judgment 6 .Problems with abstract thinking

7 .Misplacing things 8 .Changes in mood or behavior

9 .Changes in personality 10 .Loss of initiative

Alzheimer’s disease is an irreversible, progressive brain disease that slowly destroys memory and thinking skills.

Alzheimer

Protein misfolding diseases(Alzheimer’s)

Zeinab Mokhtari

Introduction

Alzheimer’s disease

Monday, July-5-2010

Protein misfolding diseases

Preventing amyloid aggregate formation

References

20

The aggregation of β-amyloid (Aβ) peptide → Alzheimer’s disease (AD)

Aβ-42 peptide is the key target in the finding of inhibitors of AD-related amyloid formation.

low molecular weight drugs

Aβ-42 monomer–monomer interactionspreventing amyloid aggregate formation

High temperature, low pH, and salt conditions

Alzheimer

21

the effect of α-D-mannosylglycerate (MG) and its structural analogs on the inhibition of Alzheimer’s Aβ aggregate formation and neurotoxicity

Thermal stress Freezing Thawing Drying

MG

MG strongly inhibits amyloid formation of Aβ-42 and its neurotoxicity in vitro.

Alzheimer

22

ThT-induced fluorescence assay and AFM image analysis

no inhibition effect

inhibition effect

Alzheimeramyloid aggregates

→ new emission maximum

23

AFM images of Aβ42 (25 mM) samples incubated with control, α-D-mannosylglycerate, α-D-mannosylglyceramide, mannose, glycerol and methylmannoside at 100 mM concentration.

Alzheimerinhibition effect

24

carboxyl group

Alzheimer

25

Sequence (Three-Letter Code)H - Asp - Ala - Glu - Phe - Arg - His - Asp - Ser - Gly - Tyr - Glu - Val - His - His - Gln - Lys - Leu - Val - Phe - Phe - Ala - Glu - Asp - Val - Gly - Ser - Asn - Lys - Gly - Ala - Ile - Ile - Gly - Leu - Met - Val - Gly - Gly - Val - Val - Ile - Ala - Thr - Val - Ile - Val - Ile - OH

DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIATVIVISequence (One-Letter Code)

covering the ‘‘hot spots’’ responsible for Ab fibrillationpenta peptides such as KLVFF

electrostatic interactions between residues

hydrophobic interactions between highly apolar residues

Alzheimer

26

Some References

peptides 29 (2008) 578 –584

Nanomedicine: Nanotechnology, Biology, and Medicine 1 (2005) 300– 305

Archives of Biochemistry and Biophysics 469 (2008) 4–19

Journal of Molecular Biology (2006) 362, 347–354

Biochimica et Biophysica Acta 1764 (2006) 443–451

27

Everything is okay in the end.If it's not okay, then it's not the

end.