biologia celular e molecular ii cell cycle deregulation and cardiovascular diseases ana rita lobo...

Biologia Celular e Molecular II

Cell cycle deregulation and cardiovascular diseases

Ana Rita LoboDiogo Matos

Inês Matos


Objectives

• Cell cycleo InterphaseoMitosis

• Control System of the Cell Cycle

• Cell cycle machinery and Stroke


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.


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.


Interphase

• The interphase stage of the cell cycle includes three distinctive parts:

o G1 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 G2 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


Mitotic Phase• The mitotic phase is the period in the cell

cycle where occurs, the nucleous division. The mitotic process includes 4 phases:

o Prophaseo Metaphaseo Anaphaseo Telophase

• After the mitotic phase, the cytokinesis occurs: microfilaments contract during cleavage and assist the division of the cell into two daughter cells.


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.


Control System of the Cell Cycle

Elements involved:• Cyclins-dependent kinases (CDKs)• Cyclins • CDK inhibitor proteins (CKIs)• Retinoblastoma protein (Rb)• Cyclical Proteolysis


CDKs

• The main components of the control system of the cell cycle are a member of a kinases’ family known as cyclin-dependent 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

Cyclin dependt kinase (CDK)


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 G1/S-phase cyclins, S-phase 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.


How Do CDKs Control the Cell Cycle?


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.


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 G1-S regulation activity in the beginning of the cell cycle. There are some types of CKIs such as P15,P16,P18 and P19.


Retinoblastoma protein (Rb)

• Important target of G1 CDKS • In mid- to late- G1, Rb is phosphorylate by

cyclin D1- cdk4/6 and cyclin E-cdk2 complexes

• Rb (hyperphosphorylated) is no longer repressed by E2F

• E2F binds with DP

• Activate genes required for S phase progression


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


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.


Cell cycle machinery and StrokeIn 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



• 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 E2F sequestration.


Cell cycle machinery and Stroke In vitro evidence

Ischemic injury conditions:

• Lose of CKIs example: CDK inhibitor p27 is reported loss of CKI following oxygen

glucose deprivation (stroke)

• Increase in Cyclins example: cyclin D1 protein levels and activation of Cdk2 after stroke

• Rb is phosphorylated following hypoxia/reoxygenation

• Increase in E2F mRNA transcription

Activation of the cell cycle


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



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



• Proceeding 1:use drugs that inactivate the cell cycle, such as CDK inhibitors like flavopiridol

• Conclusion 1: the cortical neurons have been protected



• Proceeding 2: genetic manipulation of components of the cell cycle

• Conclusion 2: in mice with expressing kinase dead cdk4 or null for its regulator cyclin (D1) are resistent to hypoxia mediated ischemic death



• Proceeding 3: envision of the cell cycle pathway with E2F null

• Conclusion 3:cortical neurons derived from E2F null mice are less susceptible to death by hypoxia

Furthermore E2F deficiency improves the recovery of neurons from loss of synaptic transmission



Taken together, these in vitro evidence strongly implicate the reactivation of cell cycle components in ischemic neuronal

death.


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)

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 G1 and antecipates the S phase



• 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



Bibliography• Alberts B., Bray D., Lewis J., M. Raff, Roberts K., & Watson J.D. (1994) Molecular

Biology of the Cell, 3rd 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+disea

ses&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.)

http://www.nature.com/scitable/topicpage/cdk-14046166

http://www.nature.com/scitable/topicpage/cdk-14046166

http://atvb.ahajournals.org/content/21/9/1421.short

http://atvb.ahajournals.org/content/21/9/1421.short

https://sites.google.com/site/kefalikinisi/home/fisiologia-humana-1/celula-e-celulas/ciclo-celular

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+diseases&hl=pt-PT&as_sdt=0

http://scholar.google.pt/scholar?start=10&q=deregulation+in+cell+cycle+and+cardiovascular+diseases&hl=pt-PT&as_sdt=0

biologia celular e molecular ii cell cycle deregulation and cardiovascular diseases ana rita lobo...

Documents