Done by: Rana Abdulnaser Alhakim رنا عبدالناصر الحكيمي

Decreases Expression of PGC-1α in the Alzheimer Disease Brain Impaire Mitochondrial Function and Distribution

Introduction

APP

Amyloidogenic pathway

Non- amyloidogenic pathway

Figure (1)

Peroxisome proliferator-activated receptor c coactivator 1 α (PGC1)

PGC1 α is a positive regulator of mitochondrial biogenesis and respiration, adaptive thermogenesis, gluconeogenesis as well as many other metabolic

The expression of PGC1α is highly inducible by physiological cues, including exercise, cold and fasting.

A central function of PGC1 α that is intimately linked

to mitochondrial biogenesis is the detoxification of reactive oxygen species (ROS) by regulating the expression of numerous ROS-detoxifying enzymes.

Figure (2)

Some previous studies studied the affect of Alzheimer disease on mitochondrial function Mitochondrial dysfunction in AD may involve

the action of APP and Aβ, as they were reported to target the mitochondria and cause mitochondrial dysfunction

(Caspersen et al., 2005; Devi et al., 2006; Manczak et al., 2006).

AD pathology is associated with decreased expression and activity of proteins involved in mitochondrial bioenergetics and mitochondrial dysfunction (Yao et al., 2009).

Materials & Methods

A human neuroblastoma M17 cell line ( this cell lines expresses human Swedish mutation APP695 or control). To study affect of Aβ on PGC-1α expression

Human neuroblastoma cell line SH-SY5Y control (SH-SY5YCon) and SH-SY5Y cells in which Fe65 was knocked down (SH-SY5Y-Fe65KD).To study affect of AICD on PGC-1α expression

\

(AβPP) transgenic mice (Tag2576 line) and the non-transgenic wild-type (WT) .To study affect of Aβ ON

mitochondrial distribution & The affect

of glucose on amyloidogenesis

DKO MEFs reconstituted with empty expression vector pcDNA3.1 (PS1/2) or with pcDNA3.1 vectors directing the expression of WT human PS1 or one of the following PS1- FAD mutations: P267S, A285V, T354I, or L392V.To study affect of γ-secretase on PGC-1α expression

Fetal bovine serum. Penicillin streptomycin. Humid incubator with CO2 at suitable T SH-SY5Y cells, mice (Tag2576 line), & DKO MEFs cell were incubated with the γ-secretase inhibitor and AICD peptide, BrDU, Heavy & light amino acids respectively.

CULTURE MEDUIM

Immunoblot analysis: Used to detect expression level of proteins (PGC-1α, BACE-1, γ- secretase, α- secretase, Aβ, presenilin(1,2), AICD and NRF.

Real time PCR & microarray: Used to sequence RNA and detect expression level of mRNA .

StaticalAnalysis

Results & discussion

Why PGC-1α expression was decreased in AD ?

mutation in γ-

secretase

AICD

Mutation in APP gene or

regulatory genes

AβGlucose

FOXO3a

dementia

PS1-FAD mutations decreased PS1’s ability to enhance PGC-1a mRNA expression & AICD increase PGC-1α expression

Figure(3): The effect of PS1 and AICD on the expression of PGC-1a and PGC-1a target genes.

γ- Secretase regulate PGC-1α expression

PGC-1α gene

Figure (4)

Mitochondrial biogenesis protein are reduced in hippocampal tissues from AD patient

Figure(5): (PGC-1α) expression in the Alzheimer disease (AD) brain are determined in presence of both AD β-amyloid (Aβ) neuropathology (a) and dementia(b).

(a)(b

)

AβControl CDR

Reduced mitochondrial biogenesis causes mitochondrial dysfunction in

PGC-1a knockdown cells

Figure (6): Down-regulation of PGC-1a affect on expression of mitochondrial biogenesis proteins and mitochondrial content in M17 cells.

Mitochondria with new DNA synthesis exist largely in cell bodies of AβPP neurons.

Figure(7): # of mDNA synthesis in cell body and neurite in both wild type neuron cells and AβPP neuron cells, BrdU staining are used to follow the mDNA.

)

How can Aβ decreases PGC-1α expression?

Poly(ADP-ribose)

polymerase-1 (PARP

SIRT PGC-1α

Aβ ROS

ATP

PKACREPAMPK

Figure (8)

How can dementia decreases PGC-1α production?

FOXO3a

ROSPGC-1α

IMPAIRED GLUCOSE

METABOLISM

Aβ Dementia

Figure (9)

Increased concentration of glucose inhibits (PGC-1α) expression and promotes β-amyloid (Aβ) generation in Tg2576 neurons

Figure(10): concentration of PGC-1α and Aβ in high concentration of glucose and the affect of PGC-1α concentration on α secretase activity.

Conclusion

Decrease expression of PGC-1α contributes to mitochondrial dysfunction and affect on mitochondrial distribution.

PGC-1α activate α- secretase and suppress β- secretase genes, so decreases in PGC-1α lead to reveres this mechanisms and increase A β production

Increase PGC-1α production may represent a potential pharmacologic approach for the treatment of AD.

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