2015.02.09.

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Signaling pathways

Apoptosis1. Introduction2. Extrinsic pathway3. Intrinsic pathway

Apoptosis

apoptosis ↔ autophagy↔ necrosis

1.

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T cell

Viral infection

Death receptors

Cell stress (growth factor depletion, cytoplasmic stress, free radicals), serum starvation

Ionizingradiation

Death receptors

Extrinsic pathway: ‐ Ligands: cytokines, TNF, Fas ligand‐ Receptors: cytokine receptors, TNF receptor, Fas receptor

Intrinsic pathway:1. Withdrawal of survival factors2. Direct mitochondrial2. ER stress3. p53‐mediated4. Viruses

Apoptotic pathways

Survival factor receptors

p53

ER

2.

caspase 3pro‐caspase 3

Cyt c

Apoptotosome

Apaf‐1

CADI‐CAD

CAD

CAD

Intrinsic pathway of apoptosis

Bax & Bak

Radiation: UV, ionizing radiation

Cellular stress: hypoxia

I‐CAD

APOPTOSIS

APOPTOSIS

Apaf‐1procaspase 9

Cyt c

3.

BAX: BCL2‐associated X protein BAK: BCL2 antagonist/killer CAD: caspase‐activated DnaseCyt c: cytochrome CApaf‐1: apoptotic protease activating factor‐1

caspase 9

3b.

Knockout mice

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4.

Caspase cascade

The three classes of Bcl‐2 proteins

PROTECTORS

KILLERS

REGULATORS

5.

Regulation of apoptosis by Bcl‐2 proteins6.

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IAP (inhibitor of apoptosis protein)

Smac (second mitochondrial activator of apoptosis)

IAP and Smac/DABLO

SMAC/DIABLO

IAPCaspase 3

Cyt C

Caspase 9

APOPTOSIS

DNA fragmentation

7.

Roles of IAPs and anti‐IAPs in apoptosis8.

caspase 3pro‐caspase 3

Cyt c

Apoptotosome

Apaf‐1procaspase 9

caspase 9

CADI‐CAD

CAD

I‐CAD

CAD

Intrinsic pathway of apoptosis – the ER stress

Ca++Ca++

Ca++

Ca++

Ca++ Ca++

Ca++

Ca++

ER stress: misfolded proteins

pro‐caspase 12caspase 12

IP3RBax & Bak

Ca++

Ca++

Ca++Ca++

Ca++ Ca++

Ca++

Radiation: UV, ionizing radiation

Cellular stress: hypoxia

DNA damage

APOPTOSIS

APOPTOSIS

Cyt c

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ER stress‐induced apoptosis9b.

caspase 8

caspase 3pro‐caspase 3

FASL

FAS

FADD

pro‐caspase 8

APOPTOSIS

cytokine

Cytokinereceptor

TRADDFADD

pro‐caspase 8

TNF‐α

TNFR1receptor

TRADDFADD

pro‐caspase 8

The extrinsic pathway of apoptosis

death domain

INITIATOR CASPASE

EFFECTOR CASPASE

CAD: caspase‐activated DnaseI‐CAD: inhibitor of CAD

CADI‐CAD

CAD

I‐CAD

CAD

Death receptors

APOPTOSIS

10.

DISC

TRADDFADD

caspase 8

pro‐caspase 8

caspase 3pro‐caspase 3

Bid

t‐Bid

Cyt c

Apoptotosome

Apaf‐1procaspase 9

caspase 9caspase 6+7

CADI‐CAD

CAD

I‐CAD

CAD

Membrane –bound FASL

FAS

death domain

Death receptor

Bax & Bak

The extrinsic pathway ‐enhancement

Secreted FASL

APOPTOSIS

APOPTOSIS

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Signaling through PI 3‐kinase promotes cell survival

Activated PI 3‐kinase

PIP2 PIP3

PDK1

PH Domains

Activated receptorTyrosine kinase

PKB

ActivePKB

Dissociation

Activation of PKB by PDK1

Phosphorylation of BADBAD

Inactive death‐inhibitory proteinActive death‐inhibitory protein

InactiveBAD

14‐3‐3protein

Inhibition ofapoptosis

mTOR

RTK

12.

Withdraval of survival factor → apoptosis

3 ways that survival factors can inhibit apoptosis 13.

M

G1

G2S

Cell cycle

UUU

E2FpRB

E2F

pRB

CyclinE

CDK2

p14

p53p53

p21

Degradation               Apoptosis

Cell cycle arrest

proteasomeRadiation

A key role for p53

MDM2

CyclinD1

CDK4

P p21

p53

p16

14.

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p53

APOPTOSIS

Caspase activation

nucleus

Cytosolic apoptotic pathway

Mitochondrial apoptotic pathway

15.