Lecture 7 Flashcards
What is cell signalling?
Cells interacting with other to perform their different functions
How does the cell take in signals from the outside environment?
Cell signal receptors and proteins inside of the cell
What do the signals determine?
The cells determine things like if the cell is going to survive, divide, differentiate or die
What are the different types of cell signalling?
Endocrine - signals that go into the blood stream (hormones) and travel around the body [can travel the furthest in the body]
Paracrine - signalling cells send there signals to local target cells there signals don’t travel very far
Neuronal - neurotransmitters crossing the synapse to a target cell that is usually another Neuron
Contact dependent (juxtacrine) - the signal is bound to the membrane of a cell and the signal receptor is bound to the other cell so contact has to be made for the signal to be sent
Autocrine - cells can signal to themselves
How does cell signalling work?
- A stimuli is received from outside of the cell (a molecule is bound to the signal receptor on the cells surface)
- Transducers then relay the signal from the surface of the cell further into the cell
- Amplifiers take the signal and then amplify and spread out the signal by converting the signal to more than one molecule
- Messengers send the signal to the specific targets within the cell
- Sensors and effectors then use the signal and action it within the cell leading to the cellular response (e.g proliferation, secretion, metabolism and learning and memory)
What is a generic growth factor signalling cascade?
- Gareth factors outside of the cell bind to growth factor receptors on the cells surface
- The GF then signals to another molecule often causing a phosphorylation cascade
- Different proteins are made activated by the phosphorylation that could lead to an increase in things like translation of proteins or transcription of DNA
Which protein that when activated inappropriately is responsible for many form of cancer?
The c-Myc protein
What are two of the most common cell signalling pathways that have been identified and linked to cancer?
- EGF/MAPK pathway
- p53 signalling pathway
What does EGF/MAPK stand for?
Epidermal growth factor MAP kinase pathway
What happens during the EGF/MAPK signalling pathway?
- The growth factor binds to the receptor on the cells surface (tyrosine kinase) which autophosphorylates
- Grb2 and SOS recognise the phosphorylation of the proteins and they will bind to it (transducers)
- Ras protein (a GTPase) will also go and bind to the tyrosine kinase and then interact with the Raf proteins (could be either Raf-1, A-Raf or B-Raf depending on the type of cell)
- The Raf proteins become phosphorylated, which then phosphorylates MEK 1 and 2
- MEK 1 and 2 then phosphorylate ERK 1 and 2
- Then proteins Ets, Elk1, SAP1 and cPLA2 become phosphorylated (these are the effectors)
- These phosphorylated proteins travel into the nucleus and cause the cell to proliferate through the phosphorylation of the c-Myc protein
When does the p53 protein become activated?
It becomes activated when there is DNA damage to a cell, cell cycle abnormalities or hypoxia
How is the p53 protein activated?
P53 is usually bound to the mdm2 protein, when they are separated the p53 protein becomes activated
What are the 2 pathways that the p53 protein can send the cell down?
- It can start cell cycle arrest, leading to DNA repair and finally the restarting of the cell cycle
Or - It can cause apoptosis and cause the death and elimination of the damaged cells
What do cancer cells not do that makes then proliferate the way they do?
Normal cells have contact-inhibition which means that when cells are growing and they touch others they stop growing, meaning on things like a Petri dish the bottom of the dish would only be covered in a mono layer of cells. Cancer cells don’t have the contact-inhibition and they just keep proliferating
What do oncogenes do?
Oncogenes cause the cells to uncontrollably proliferate and it can cause tumours in cancer
