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44 Cards in this Set
- Front
- Back
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What are the 4 types of receptors? |
Ligand gated ion channels G protein- coupled receptors Kinase linked receptors Nuclear receptors |
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What is an antagonist? |
A substrate which prevents the effect of the receptors activation |
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What is an agonist? |
Promotes receptor response |
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What are 'orphan receptors'? |
Receptors for which the binding ligand has not been identified. |
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How many trans-membrane domains (proteins) are there in a GPCR? |
7 |
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How are GPCRs sometimes referred to? |
'7TM' or 'Heptahelical' receptors |
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Where are G proteins bound? |
In the intracellular domain |
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Why are they called 'G' protein coupled receptors? How do 'G' proteins control the receptor? |
Due to their interaction with Guanine nucleotides GDP= off GTP= on |
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What are the sub units ? |
alpha: Where GDP/GTP bind beeta/gamma: Where alpha interacts |
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What happens when a ligand binds to the receptor? (cycle) |
The alpha sub-unit and receptor interact GDP is converted to GTP G protein is activated G protein alpha interacts with downstream target proteins GTPase in the alpha sub-unit hydrolyses a phosphate from GTP, leaving GDP, inactivating the alpha sub-unit and it rebinds to the receptor. |
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What is bi-directional control? |
When 2 GPCRs have opposite effects on the same receptor |
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How does bi-directional control work in Adenylate cyclase? |
Acetylcholine ligand binds to Ri receptor causing muscle contraction Adrenaline binds to Rs receptor causing muscle relaxation |
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How does Adrenaline cause muscle relaxation when bound to Rs receptor? |
Activates G protein alpha subunit Adenylate cyclase activated Aden. cyclase catalyses conversion of ATP to cAMP cAMP activates Protein Kinase Kinase phosphorylates and activates target protein |
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Which G protein does Acetylcholine receptor M1 bind to? |
Gq |
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Which enzyme does Gq activate? |
Phospholipase Cbeeta |
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What happens when Gq activates Phospholipase? |
Phospholipase catalyses the conversion of PIP2 to IP3 and DAG DAG activates protein kinase IP3 causes an increase in cytosolic calcium, which binds to target proteins |
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Which receptor is important in asthma treatment? |
Beta 2 |
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How do beta 2 agonists help asthma sufferers? |
They activate G protein S, triggering smooth muscle relaxation cascade |
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Name 2 short acting agonists |
Salbutamol, Terbutaline |
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Name a long acting agonists |
Salmeterol |
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Name a 24 hour agonist |
indicaterol |
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Which beta adreno receptor is located in cardiac muscle? |
beta 1 |
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How do beta 1 agonists increase heart rate and blood pressure? |
Activating adenylate cyclase/ protein kinase to increase cardiac muscle contraction |
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How does Propanolol combat high blood pressure? |
It acts as an antagonist to the Beta 1 adreno receptor |
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Why might you NOT give Propanolol to an asthma sufferer? |
It is also a beta 2 antagonist, preventing the smooth muscle relaxation pathway and causing broncho constriction |
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How can the alpha subunit influence ion channels? |
It can bind to ion channels and cause them to open, such as potassium channels in the heart |
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What are type 3 receptors? |
Kinase linked |
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How many trans-membrane proteins are there in kinase linked receptors? |
Just 1, across whole membrane |
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Where are the components of the kinase linked receptor located? |
Receptor on the outside Kinase enzyme (inactive) on the inside |
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What happens when kinase linked receptors are activated? |
They dimerise The tyrosine is phosphorylated an adaptor protein binds to the dimer the adaptor signals to other kinases to initiate cascades |
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Name 2 types of kinase linked receptor |
Tyrosine kinase Serine/Threonine kinase |
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What are cytokine receptors and how do they work? |
A type of kinase linked receptor Work similarly, except the 'Jak' protein is activated by phosphorylation and the 'stat' adaptor protein dimerises to activate gene transcription |
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What is the HER2 receptor? |
A tyrosine kinase linked receptor upregulated in around 20% of breast cancer cases Activates epithelial cell growth |
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How can the HER2 receptor be exploied for cancer treatment? |
Trastzumab antibody used as a antagonist to prevent epithelial cell replication |
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Name 2 kinase linked receptors in cancer |
KIT, HER2 |
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How is KIT inhibited |
Glivec binds to kinase domain of adaptor protein, preventing cascade |
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What are type 4 receptors? |
Nuclear receptors |
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What type of molecules can interact with Nuclear receptors? |
Hydrophobic hormones (can cross plasma membrane) e.g. steroid and thyroid hormones |
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What is a special feature of nuclear receptors? |
They can cross the nuclear envelope, not embedded in a membrane They can interact directly with DNA |
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What are the two types of nuclear receptor? |
Cytosolic and Nuclear |
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How are cytosolic receptors activated? |
Usually associated with inhibitory protein e.g. HSP90 When ligand interacts they are released and migrate to nucleus |
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How are nuclear receptors activated? |
Located in the nucleus with heterodimer with RXR Bound to a co repressor which disassociates when ligand binds |
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How does Aldosterone work? |
Binds to mineralcorticoid receptor in kidney Stimulates transcription of DNA to synthesise NA+ channel in the loop of Henle Increases salt and water retention |
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What inhibits the action of aldosterone? |
Spironolactone (inhibits intracellular receptor of aldosterone) |
