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29 Cards in this Set
- Front
- Back
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What is endocrine signalling?
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When a signalling molecule is transmitted through the blood, from one tissue to another.
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What is autocrine signalling?
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When cell signals are secreted and act on the secreting cell. "Self pleasure."
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What are cytokines?
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Signalling molecules that act on immune cells.
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What is paracrine signalling?
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A local signal, to surrounding cells.
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What is juxtacrine signalling?
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A signal transmitted when cells are touching. Transmembrane proteins on both cells must touch.
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When is a cell "blind" to a stimulus?
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When it lacks receptors for that stimulus.
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What are some cell processes that require signal transduction? (5)
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-activations of genes
-alterations of metabolism -cell proliferation -cell death (apoptosis) -stimulation or supression of locomotion |
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What are the two classes of receptor proteins?
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-Intracellular
-Cell Surface receptors |
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What do intracellular receptors bind?
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-steroid hormones
-throid hormone -retinoic acid -vit. D derivatives |
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What two main enzyme activation processes are used?
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-phosphorylation of the enzyme
-use of a GTP binding protein |
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GPCR
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G-protein coupled receptor
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How many subunits does a G-protein have?
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3 - α,β, and γ subunits
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How does the G protein work?
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The α subunit gives up GDP, and binds GTP. This causes the α subunit to disassociate and allows it to interact with an effector protein (eg. adenylyl cyclase) to create a second messenger. The β and γ subunits (which remain together) can also interact with other proteins to amplify the signal. The α subunit has GTPase activity, and eventually hydrolyzes GTP to GDP, which causes the three G-protein subunits to reassociate in the inactive state.
βγ |
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What kinds of proteins do G-proteins effect downstream?
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-phosphodiesterases
-adanylyl cyclases -phospholipases -ion channels |
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The strength of signal amplification is determined by...
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-the lifetime of the ligand-receptor complex
-the amount and lifetime of the receptor-effector protein complex -modulation of signal response |
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What does arrestin do?
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Binds to the receptor, preventing activation of the G-protein. Desensitizes the cell to the signal.
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What is down-regulation?
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Endocytosis of membrane-bound receptors.
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In the cAMP pathway of signal transduction, what does cAMP do?
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Activates Protein Kinase A (PKA).
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What does PKA do in the cAMP pathway?
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phosphorylates cytosolic proteins (turning them on), and enter nucleus to activate CREB (aAMP responsive element).
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What do phosphodiesterases do?
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Catalyzes cAMP to 5'AMP, ending response.
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In the cAMP pathway, what is the difference between Stimulatory G-proteins, and Inhibitory G-proteins?
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Simulatory G-proteins activate adanylyl cyclase. Inhibitory G-proteins turn it off.
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How does Vibrio cholerae cause disease?
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Cholera toxin causes inactivation of the GTPase activity on the α subunit of a stimulatory G-protein, leaving it in the "on" position, causing increased cytosolic cAMP levels.
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How does Bordetella pertussis cause disease?
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Pertussis toxin causes the inactivation of the G-protein. It is locked in the "inactive" state.
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DAG
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diacylglycerol
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IP3
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inositol 1,4,5-trisphosphate
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PIP2
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phosphatidyl inositol diphosphate
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How does the DAG, IP3 pathway work?
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-signal binds to receptor.
-G-protein is activated -phospholipase C is activated: cleaves PIP2 into DAG and IP3 -IP3 binds to calcium channel on ER membrane: channel opens and cytosolic calcium concentration rises. -Calcium and DAG interact with PKC |
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What is an example of what the βγ subunit of the G-protein can activate?
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-a cell membrane K+ channel
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RTK
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Receptor Tyrosine Kinase
(a transmembrane protein with an intracellular kinase domain and an extracellular domain that binds ligand) |
