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22 Cards in this Set
- Front
- Back
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What is signal transduction?
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The diverse sequence of events btw receptor activation and cellular responses.
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What are receptors mostly made of?
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Plasma membrane proteins, but some oare cytosolic proteins.
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What is down regulation?
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Refers to the change in total number of receptors in target cells.
It is a decrease in number of receptors. Occurs when there is a high [ ] of a messenger is maintained for some time. Results in REDUCTION of the target cells' responsiveness to intense stimulation. |
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What is Up-Regulation?
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Increase in # of receptors.
Results in HYPERSENSITIVITY. Occurs when there is low [ ] of a messenger. |
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What are 4 types of receptors?
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Ion channel
Enzyme activity Interaction with kinase Interaction with G proteins |
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What is the effect of a receptor on ion channel activity?
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It opens the pore upon binding to a messenger--> change in membrane voltage as a result of inflowing of ions--> induces cellular response.
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What is the effect of a receptor on enzyme activity?
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This type of receptor has tyrosine kinase activity which leads phosphorylation--> activation of proteins.
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What is the effect of a receptor interacting with a separate kinase?
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In this case, the receptor and its bound JAK (Just Another Kinase) work as a unit. When the receptor is bound by a first messenger, it induces a change in conformation of the receptor which leads to the activation of JAK. JAK then goes on to phosphorylate other proteins.
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What is the effect of a receptor interacting with a G protein?
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First messenger + receptor--> allows GTP to bind to alpha subunit of G proteins.
Then G protein--Alpha subunit dissociates from beta and gamma subunits and links up with plasma membrane effector protein. This effector protein gets activated. This leads to a change in membrane potential and generates a SECOND MESSENGER. The 2nd messenger then enters the cell. |
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What are some examples of 2nd messengers?
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Ca ion, cAMP, DAG, IP3, and arachadonic acid.
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What is adenylate cyclase and what is its function?
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It's an effector protein that is regulated by a Gs protein.
Its function is it catalyzes the conversion of ATP to cAMP. |
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What is the function of cAMP?
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It binds to and activates cAMP-dependent protein kinase, specifically protein kinase A.
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What is the function of PKA?
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Phosphorylates other proteins.
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What terminates the action of cAMP?
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When it gets broken down to a noncyclic form by the action of phosphodiesterase.
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What is Phospholipase C?
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It's the second effector protein of the Gq protein.
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What is the function of Phospholipase C?
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Catalyzes the breakdown of PIP2 to IP3 and DAG.
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What is the function of IP3?
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It binds to Ca channels in ER and cause it to release Ca.
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What is the function of DAG?
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It activates Protein Kinase C which then phosphorylates a large number of other proteins.
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In what way can Ca ion act as a 2nd messenger?
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It can bind to calmodulin, which then activates calmodulin-dependent protein kinase (CaM kinase).
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What is the function of Phospholipase A2 as an effector protein?
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Catalyzes the conversion of Phospholipid A2 to arachidonic acid.
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What are the end products of Arachidonic acid?
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Eicosanoids, i.e. prostaglandins, thrombozanes, and leukotrienes.
NOTE: Arachidonic acid is also a second messenger. |
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How does signal transduction terminate?
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1. Decreasing [ ] of 1st messengers.
2. Inactivate the receptors. |
