Biologia Celular e Molecular II Cell cycle deregulation

Biologia Celular e Molecular II Cell cycle deregulation and cardiovascular diseases Ana Rita Lobo Diogo Matos Inês Matos

Biologia Celular e Molecular II Objectives • Cell cycle o Interphase o Mitosis • Control System of the Cell Cycle • Cell cycle machinery and Stroke

Biologia Celular e Molecular II Cell Cycle • The cell cycle is the series of events which take place in the cell and lead to its duplication by means of replication and duplication of its previous contents.

Biologia Celular e Molecular II Cell cycle’s phases • The cell cycle is generally divided into two phases: o Interphase - the cell spends most of its time performing the functions that make it unique. o Mitosis - the cell divides into two daughter cells.

Biologia Celular e Molecular II Interphase • The interphase stage of the cell cycle includes three distinctive parts: o G 1 phase- follows mitosis and is the period in which the cell is synthesizing its structural proteins and enzymes to perform its functions; o S phase- the DNA within the nucleus replicates o G 2 phase- the cell prepares for mitosis. Proteins organize themselves to form a series of fibers called the spindle, which is essential to chromosome movement during mitosis

Biologia Celular e Molecular II Mitotic Phase • The mitotic phase is the period in the cell cycle where occurs, the nucleous division. The mitotic process includes 4 phases: o o Prophase Metaphase Anaphase Telophase • After the mitotic phase, the cytokinesis occurs: microfilaments contract during cleavage and assist the division of the cell into two daughter cells.

Biologia Celular e Molecular II Control System of the Cell Cycle • In the majority of eukaryotic cells, the control systems of the cell cycle activate its progression in three points.

Biologia Celular e Molecular II Control System of the Cell Cycle Elements involved: • Cyclins-dependent kinases (CDKs) • Cyclins • CDK inhibitor proteins (CKIs) • Retinoblastoma protein (Rb) • Cyclical Proteolysis

Biologia Celular e Molecular II CDKs • The main components of the control system of the cell cycle are a member of a kinases’ family known as cyclindependent kinases that can modify various protein substrates involved in cell cycle progression. CYCLINS • Cyclins are a family of proteins that have no enzymatic activity of their own but activate CDKs by binding to them. Cyclin dependt kinase (CDK)

Biologia Celular e Molecular II How Do CDKs Control the Cell Cycle? • All cyclins are named according to the stage at which they assemble with CDKs. Common classes of cyclins include G 1/S-phase cyclins, Sphase cyclins, and M-phase cyclins. • Because cyclin-CDK complexes recognize multiple substrates, they are able to coordinate the multiple events that occur during each phase of the cell cycle.

Biologia Celular e Molecular II How Do CDKs Control the Cell Cycle?

Biologia Celular e Molecular II Inhibitor phosphorilation and CKIs(CDK inhibitor proteins) • The rise and fall of the cyclin levels are the main events that control the activity of CDKs during the cell cycle. However, other mechanisms help the activity of CDKs in specific stages of the cycle.

Biologia Celular e Molecular II Inhibitor phosphorilation and CKIs(CDK inhibitor proteins) • The phosphorilation in a pair of amino acids on the top of the kinases’ active site inhibits the cyclin-cdk complex. • Cells usually use CKIs to help them in the G 1 -S regulation activity in the beginning of the cell cycle. There are some types of CKIs such as P 15, P 16, P 18 and P 19.

Biologia Celular e Molecular II Retinoblastoma protein (Rb) • Important target of G 1 CDKS • In mid- to late- G 1, Rb is phosphorylate by cyclin D 1 - cdk 4/6 and cyclin E-cdk 2 complexes • Rb (hyperphosphorylated) is no longer repressed by E 2 F • E 2 F binds with DP • Activate genes required for S phase progression

Biologia Celular e Molecular II Cell cycle’s deregulation and cardiovascular diseases • Hypothesis: One signal which may control ischemic neuronal death is the inappropriate activation of cell cycle regulators including cyclins, cyclin dependent kinases (CDK) and endogenous cyclin dependent kinases inhibitors (CDKI). Aberrant activation of these elements triggers neuronal death

Biologia Celular e Molecular II Stroke • Occluded or ruptured of blood vessels and in some cases cardiac arrest. Neurons in the affected brain region are prived of oxigen and glucose. Ischemic neuronal death is determined by location, severity and duration of insult.

Biologia Celular e Molecular II Cell cycle machinery and Stroke In vitro evidence

Biologia Celular e Molecular II Cell cycle machinery and Stroke In vitro evidence J. Rasidian, G. O. Iyirhiaro, D. S. Park, Cell cycle machinery and stroke, BBA – Molecular Basis of Disease (2006), doi: 10. 1016 / j. bbadis. 2006. 11. 009

Biologia Celular e Molecular II Cell cycle machinery and Stroke In vitro evidence • Normal conditions: • The levels of activity of key cell cycle are downregulated; • More activity of CKIs; • The levels of hypophosphorylated Rb increases resulting in greater E 2 F sequestration.

Biologia Celular e Molecular II Cell cycle machinery and Stroke In vitro evidence Ischemic injury conditions: • Lose of CKIs example: CDK inhibitor p 27 is reported loss of CKI following oxygen glucose deprivation (stroke) • Increase in Cyclins example: cyclin D 1 protein levels and activation of Cdk 2 after stroke • Rb is phosphorylated following hypoxia/reoxygenation • Increase in E 2 F m. RNA transcription Activation of the cell cycle

Biologia Celular e Molecular II Cell cycle machinery and Stroke This only showed the activation of cell cycle components and does not adresss the issue of whether this signal is required for death

Biologia Celular e Molecular II Cell cycle machinery and Stroke J. Rasidian, G. O. Iyirhiaro, D. S. Park, Cell cycle machinery and stroke, BBA – Molecular Basis of Disease (2006), doi: 10. 1016 / j. bbadis. 2006. 11. 009

Biologia Celular e Molecular II Cell cycle machinery and Stroke • Proceeding 1: use drugs that inactivate the cell cycle, such as CDK inhibitors like flavopiridol • Conclusion 1: the cortical neurons have been protected

Biologia Celular e Molecular II Cell cycle machinery and Stroke • Proceeding 2: genetic manipulation components of the cell cycle of • Conclusion 2: in mice with expressing kinase dead cdk 4 or null for its regulator cyclin (D 1) are resistent to hypoxia mediated ischemic death

Biologia Celular e Molecular II Cell cycle machinery and Stroke • Proceeding 3: envision of the cell cycle pathway with E 2 F null • Conclusion 3: cortical neurons derived from E 2 F null mice are less susceptible to death by hypoxia Furthermore E 2 F deficiency improves the recovery of neurons from loss of synaptic transmission

Biologia Celular e Molecular II Cell cycle machinery and Stroke Taken together, these in vitro evidence strongly implicate the reactivation of cell cycle components in ischemic neuronal death.

Biologia Celular e Molecular II Cell cycle role in atherosclerosis The atherosclerotic plaque is due to an overproliferation of endothelial, smooth muscle, and inflammatory cells and macrophages The division of these cells is activated by a Allograft Inflammatory Factor (AIF-1)

Biologia Celular e Molecular II Cell cycle role in atherosclerosis • AIF-1 is not present in normal arteries, and it is produced by VSMC when they are stimulated. Constitutive expression of AIF-1 results in a shorter cell cycle, and aberrant expression of cell cycle proteins. • AIF-1 actively participates in the upregulation of VSMC’s proliferation This happens because AIF-1, alongside with calmodulin, shortens the G 1 and antecipates the S phase

Biologia Celular e Molecular II Cell cycle role in atherosclerosis • This is important to cope with the inflammatory processes. But if this happens in ordinary situations, it may cause a overproduction of VSM cells, obtructing crucial arteries of the cardiovascular system. Atherosclerotic Restenosis

Biologia Celular e Molecular II Bibliography Alberts B. , Bray D. , Lewis J. , M. Raff, Roberts K. , & Watson J. D. (1994) Molecular Biology of the Cell, 3 rd Ed. Garland Publishing, Inc. New York. • Netgraphy http: //www. nature. com/scitable/topicpage/cdk-14046166 http: //atvb. ahajournals. org/content/21/9/1421. short https: //sites. google. com/site/kefalikinisi/home/fisiologia-humana-1/celula-e-celulas/ciclo-celular http: //scholar. google. pt/scholar? start=10&q=deregulation+in+cell+cycle+and+cardiovascular+dise ases&hl=pt-PT&as_sdt=0 • • Articles • J. Rasidian, G. O. Iyirhiaro, D. S. Park, Cell cycle machinery and stroke, BBA – Molecular Basis of Disease (2006), doi: 10. 1016 / j. bbadis. 2006. 11. 009 • Michael V. Autieri, Christopher M. Carbone - Overexpression of Allograft Inflammatory Factor-1 Promotes Proliferation of Vascular Smooth Muscle Cells by Cell Cycle Deregulation (Arterioscler Thromb Vasc Biol. 2001; 21: 1421 -1426. )