Death and Rescue

1. Death and Rescue 未知死 焉知生 Regulation of cardiac myocyte cell death Lin GH

2. Death pathway there are two principal forms of cell death: Necrosis & apoptosis

3. Myocyte death as a contributing factor to cardiac pathology infarction Ischemic Injury and Myocyte Death There is evidence that apoptosis precedes necrosis and constitutes the prevailing form of myocyte death.

4. Initiator caspases Caspases as the Effector Machinery of Apoptosis Effector caspases Other caspases cysteine-dependent aspartate-directed proteases

5. Caspase cascades are highly ordered Initiator caspases effector caspases positive feedback

6. Target proteins for caspases nuclear proteins Regulatory proteins Cytoskeletal proteins

7. Apoptotic death pathway Mitochondrion- dependent Intrinsic pathway Receptor-dependent Extrinsic pathway

8. Mechanisms of Caspase Activation Activation of caspases may take place either within death receptor complexes of the cytoplasmic membrane or by a mitochondrion-dependent mechanism within the cytosol

9. Death Receptor Pathway death domain-mediated protein interactions

10. The extrinsic pathway through death receptors

11. Mitochondrial Pathway Schematic diagram showing the mechanism of cytochrome c–dependent caspase activation apoptosis-inducing factor (AIF).

12. Intrinsic pathway through the mitochondria Intracellular stresses such as increased oxidative stress, which may derive from the mitochondria themselves, activate the mitochondrial death pathway. apoptosome

13. Apaf-1 and activation of caspase-9 cytochrome c interacts with an adapter protein, apoptosis-activating factor (Apaf)-1

14. Morphological changes in mitochondria during cytochrome c release

15. Central role of mitochondria during ischemia and reperfusion Cytochrome c and the mitochondrial permeability transition pore opening of the MPTP may also influence cell death by effecting the release of cyt c and other apoptotic factors from the mitochondrial intermembrane space

16. The mitochondrial permeability transition pore cyclophilin D (Cyp-D) VDAC, voltage-dependent anion channel ANT, adenine nucleotide translocase

17. The Bcl-2 family of proteins are key regulators of the mitochondrial death pathway. Regulatory Proteins ----Bcl-2 Protein Family Mediate both proapoptotic and antiapoptotic regulation Bcl-xL Bax Bcl-2 BH1 (red), BH2 (orange), BH3 (green), and BH4 (yellow)

18. Mechanisms suggested to mediate the antiapoptotic effect of bcl-2

19. Model for the mechanism of action of Bcl-2 family proteins

20. Inhibitor of Apoptosis Proteins X-linked IAP neuronal IAP c-IAP1 c-IAP2 survivin - caspase activity caspase activation not only requires proteolytic cleavage of the enzymes themselves, but removal of inhibitory influences (IAPs) is also necessary. Since the levels of expression of IAPs (and other inhibitory proteins) appear to be high in the heart, modulation of these proteins may be a significant aspect of cardiac myocyte apoptosis.

21. Signal Transduction The commitment to apoptosis is influenced by protein kinase cascades that may be activated in the cell. whereas some protein kinases are implicated in cytoprotection, and others enhance cell death. Signal transduction pathways implicated in the regulation of cell survival and apoptosis

22. Modulation of myocyte cell death Phosphatidylinositol 3’-kinase The pathway that is most clearly implicated in cytoprotection in all cell types is the PI3K pathway This pathway is potently activated by insulin or insulin-like growth factor-1 (IGF-1).

23. Akt Signaling

24. Mitogen-activated protein kinases There are three well-characterized MAPK subfamilies that have already been mentioned, the ERKs, JNKs, and p38-MAPKs, all of which influence cell survival

25. Toward Antiapoptosis as a New Treatment Modality Targets for Intervention Initiation, regulation, and effector mechanisms offer potential molecular targets for antiapoptotic intervention.

26. Antiapoptotic strategies Decoy receptor Inhibitors of stress-activated protein kinases PI3K, ERK signaling pathway ARC IAPs BcL-2 family proteins FasL: Fas ligand; cyt. C: cytochrome c; ARC: apoptosis repressor with a caspase recruitment domain; AIF:apoptosis-inducing factor.

27. Antiapoptotic strategies Targeting the Proapoptotic Stimulus Acting on the Myocyte B-blocking agents, carvedilo ,angiotensin-converting enzyme inhibitors, reducing oxidative stress ,inhibition of death receptor stimulation Promotion of Antiapoptotic Signaling Bcl-2 protein family (eg, Bcl-2 or Bcl-xL), apoptosis repressor with a caspase recruitment domain, decoy receptors ,growth factors ( insulin-like growth factor-1, cardiotrophin-1, neuregulins), Targeting Proapoptotic Signaling proapoptotic members of the Bcl-2 protein family such as Bax, Bad, and Bid, synthetic drugs interfere with the proapoptotic activity of adaptor protein , inhibition of MPTP and intracellular signaling pathways in promoting apoptosis Targeting the Downstream Execution Phase of Apoptosis Inhibition of downstream caspases (caspase-3, -6, or -7)

28. Thank you ! Lin GH 2004/0924