molecular chaperones and handling of abnormal proteins in ... · q82 q82: age-1 q82: age-1: daf-16....

Molecular Chaperones and Handling of Abnormal

Proteins in Neurodegenerative Disorders

Prof. Michael Sherman

The screen versions of these slides have full details of copyright and acknowledgements 1

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Molecular Chaperones and Handling

of Abnormal Proteins

in Neurodegenerative Disorders

Michael Sherman

Professor of Biochemistry,

Boston University Medical School

Boston, U.S.A

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Lewy bodies

in Parkinson’s disease

Inclusion bodies

in Huntington’s disease

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A





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Soluble

abnormal proteins

Native proteins

Ubiquitin-proteasome degradation

Aggresome

MTOC (centrosome)

Microtubuli-dependent transport

Survival

Small aggregates

Toxicity

Degradation

Autophagy

Stress

Mutations

Chaperones

Refolding

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Association of neurodegenerative disorders with mutations in components

of UPS and chaperones

Gene Function Disease

Parkin E3 ubiquitin ligase PD

UchL1 Ubiquitin hydrolase PD

DJ-1 Chaperone PD

VCP Chaperone Frontotemporal dementia

Torsin A Chaperone Torsin dystonia

Ataxin 3 Ubiquitin-associated protein MJD

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Modif ication of proteins with ubiquitin

20S proteasome

E2(n)

ATP

26S proteasome

E3(n)

E2(n)

E2(n)

Ubiquitin

-C-OH

= O

Degradation of ubiquitinated proteins

ATP

E1

E1

ATP

The ubiquitin-proteasome system for intracellular protein degradation

19S particle





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ATPase CTD

Hsp70

Substratepolypeptide

CHIP

Degradation

Proteasome

CHIP connects chaperones with the degradation machinery

U-box

Ubiquitin

E2

TPR

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Small aggregates Aggresome

MTOC (Centrosome)

Microtubuli-dependent transport

Soluble proteins

Toxicity

Survival

Degradation

Autophagy

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In the process of aggresome formation components of the proteasome system

co-localize with γ-tubulin, a marker for the centrosome

19S

George DeMartino

PA28 Ubiquitin





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Microtubules are important for aggresome formation

Benomyl Control

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Mutations that prevent aggresome formation lead to toxicity of abnormal proteins

boi2/103QP

W T

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Role of HDAC6 in aggresome formation

Kawaguchi et al., Cell, 2003

BUZDMB





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Molecular chaperones alleviate neurodegeneration

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Overexpression of Hsp70 alleviates pathology in Kennedy disease

Overexpression of Hsp70 alleviates pathology in Kennedy’s disease

Adachi et al., 2003

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Overexpression of Hsp70 alleviates pathology in Drosophilamodel of MJD

Control

Warrick et al., 1999

MJD-Q78/ Hsp70MJD-Q78Hsp70





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Overexpression of CHIP alleviates pathology in Kennedy’s disease

Adachi et al., 2007

17Sittler et al.,

2001

Chemical inducer of heat shock proteins GA prevents aggregation of huntingtin

with expanded polyglutamine domain

GA 180 nM GA 360 nM

GA 18 nM GA 90 nM

DMSO

EGFP-HD72Q

Control

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A build-up of abnormal polypeptides

leads to induction of heat shock proteins





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Hsp70 Hsp90

HSF-1

HSE

HSF-1

Hsps

Heat shock response

Unfolded proteinsHeat shockOxidative stress

Heavy metals, etc.

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Defects in chaperone system are seen in neurodegenerative disorders

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Progressive loss of chaperones in Huntington’s disease mouse model

Hay et al., 2004

Age in weeks





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Suppression of the heat shock response in cells with polyQ aggregates

Cowan et al., Hum. Mol. Genet., 2003, 12: 1377-91

AR-25Q

AR-65Q

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Defects in ubiquitin-proteasome system

are seen in neurodegenerative disorders

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Measurements of activity of the proteasome pathway in a single cell

Unstable polypeptide GFP

Unstable polypeptide GFP Unstable fluorescent protein

Bence et al., Science, 2001, 292: 1552-5

0 hr lactacystin 6 hr lactacystin





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Inhibition of ubiquitin-proteasome degradation in cells with aggresomes

Bence et al., Science, 2001, 292: 1552-5

Q25 Q103

Htt

GFPu

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Proteasome subunits and Hsp70

are downregulated in Parkinson’s disease brain

Mandel et al., 2005

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Similar defects in chaperone

and ubiquitin-proteasome

systems are seen upon aging





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IGF1

FOXO

Aging

SIRT1

Caloric

restriction

Aging signaling pathways

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Decrease in expression of chaperones upon aging

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Decrease in proteasome activity upon aging





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Generation of Ubb+1

KRGGK

UBB+1Ubiquitin

Substrate

polypeptideSubstrate

polypeptide

Hope et al., 2003

DNAGCTCTCTCTTACAGACTG

∆GA

Normal RNACGA GAG AGA AUG UCU GAC

Mutant RNACGA GAG AAU GUC UGA

Normal protein +1 protein

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Age-dependence of aggregation

Morley et al., 2001

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Protein aggregation is delayed in long-lived mutants of C. elegans

Morley et al., 2001

IGF1 Age1

FOXO Daf1

Aging

Q82

Q82: age-1

Q82: age-1: daf-16





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Def ects in chaperones and UPS

Neurological problems and aging

Aging

Protein abnormalities and aggregation

Neurotoxicity

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molecular chaperones and handling of abnormal proteins in ... · q82 q82: age-1 q82: age-1: daf-16....

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