Apoptosis Oncogenes. Srbová Martina

Transcription

1 Apoptosis Oncogenes Srbová Martina

2 Cell Cycle Control point Cyclin B Cdk1 Cyclin D Cdk4 Cdk6 Cyclin A Cdk2 Cyclin E Cdk2 Cyclin-dependent kinase (Cdk) have to bind a cyclin to become active

3 Regulation of Cell Cycle 1. Cyclin-dependent kinase (Cdk) Phase specific synthesis cyclin Phase-specific phosphorylation of proteins required in the cell cycle

4 Regulation of Cell Cycle 2. Retinoblastoma protein (prb) E2F Gene transcription: DNA polymerase, dihydrofolate reductase, thymidin kinase, S phase cyclin

5 Regulation of Cell Cycle 3. Protein p53, the guardian of the genome Great DNA damage high p53 conc. In over 50% of cancers, the p53 genes are muted or lost.

6 Regulation of Cell Cycle 4. Growth factor signal transduction PDGF PDGF PDGFR conc. of GF cell division GF receptor tyrosin kinase domain PDGF activates Ras Ras-GTP activates a kinase cascade Ras inactivates itself Jun, Fos Mutation in Ras gen 30% of human cancer Y tyrosin residues

7 APOPTOSIS

8 Apoptosis Programmed cell death Elimination of unwanted cells - embryonic development - diseased cells, - tumor cells, - cells with irreparably damaged DNA shrinking of nucleus, chromatin condensation formation of small blebs apoptotic bodies Without inflammatory response

9 Membrane blebbing Fagocytosis Apoptotic bodies

10 Apoptosis Perforin Granzyme B Caspase cystein-containing aspartate proteinases

11 Death receptor pathway (extrinsic pathway) Source: DISC death inducing signaling complex

12 Mitochondrial pathway (intrinsic pathway) Bak and Bax oligomerize to form pores cytochrome c passes into cytoplasm Substrate proteolysis results in apoptosis Bcl-2-like proteins: 1) pro-apoptic BAX, BAK, BID 2) anti-apoptic Bcl-2, Bcl-X L Apaf1 apoptotic protease activating factor 1

13 Integration between the death receptor and mitochondrial pathway Death receptor pathway Mitochondrial pathway Apoptotic signal Caspase 8 Execution caspases Truncated BID Apaf- 1 Cytochrom c Substrates of execution caspases Caspase 9

14 Caspases Caspase cystein-containing aspartate proteinases Initiator caspases 2,8,9 Execution caspases 3,6,7 Caspases are created from inactive procaspases Procaspase 8 Caspase 8 Active caspase

15 Caspases Target molecules: Lamins Poly-ADP-ribosa-polymerase (PARP) DNA-dependent proteinkinase Actin

16 Detection of apoptosis Exposition of fosfatidyl serine annexin V n8/fig_tab/nrm0801_627a_f2.html

17 Detection of apoptosis DNA fragmention DNA ladder 02.html

18 ONCOGENES

19 ONCOGENES Proto-oncogenes genes that encode proteins that promote cell division or that promote resistence to apoptosis Their activating mutation or overexpression results in increased actvity unregulated cell division or resistence to apoptosis Mutations in proto-oncogens oncogens Only one allele of proto-oncogene needs to be converted to an oncogene to cause a pro-proliferative or anti-apoptic effect in a cell

20 Transforming mutation in proto-oncogenes

21 Protooncogenes Activators of cell division Growth factors ( PDGF) Growth factor receptor (PDGFR) Kinases and kinase cofactors (Cyklins, Cdk, MAPKs) Transcription factors (Myc, Jun, Fos, E2F) Signal transduction proteins ( Ras) Activators of apoptic resistence Apoptosis regulators ( Bcl-2, Bcl-X L, Mdm2)

22 Tumor suppressor genes Products of tumor supresssor genes suppress the cell division cycle or promote apoptosis Tumor suppressor gene must lose activity to contribute to cancer Both alleles of a tumor suppressor gene must be inactivated or lost in order to eliminate their tumor suppression activity from a cell Retinoblastoma (rb) and p53 genes BRCA1, BRCA2

23 Summary Apoptosis can protect organisms from the negative effect of mutation by destroying cells with irreparably damaged DNA before they proliferate. Just as an excess of growth signal can produce an excess of unwanted cells, the failure of apoptosis to remove excess or damadged cells can contribute to the cancer. Transformation into a malignant cell results from abnormalities in the normal growth regulatory program caused by gain-of- function mutation in proto-oncogens. However, loss-of-function mutation also must occur in the tumor suppressor genes for full transformation to a cancer cell

24 Sources: Devlin, T. M. Textbook of biochemistry: with clinical correlations. 6th edition. Wiley-Liss, Marks Basic Medical Biochemistry, A Clinical Approach, third edition, 2009 (M. Lieberman, A.D. Marks) Color Atlas of Biochemistry, second edition, 2005 (J. Koolman and K.H. Roehm)