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29 Cards in this Set

  • Front
  • Back
What is endocrine signalling?
When a signalling molecule is transmitted through the blood, from one tissue to another.
What is autocrine signalling?
When cell signals are secreted and act on the secreting cell. "Self pleasure."
What are cytokines?
Signalling molecules that act on immune cells.
What is paracrine signalling?
A local signal, to surrounding cells.
What is juxtacrine signalling?
A signal transmitted when cells are touching. Transmembrane proteins on both cells must touch.
When is a cell "blind" to a stimulus?
When it lacks receptors for that stimulus.
What are some cell processes that require signal transduction? (5)
-activations of genes
-alterations of metabolism
-cell proliferation
-cell death (apoptosis)
-stimulation or supression of locomotion
What are the two classes of receptor proteins?
-Cell Surface receptors
What do intracellular receptors bind?
-steroid hormones
-throid hormone
-retinoic acid
-vit. D derivatives
What two main enzyme activation processes are used?
-phosphorylation of the enzyme
-use of a GTP binding protein
G-protein coupled receptor
How many subunits does a G-protein have?
3 - α,β, and γ subunits
How does the G protein work?
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.

What kinds of proteins do G-proteins effect downstream?
-adanylyl cyclases
-ion channels
The strength of signal amplification is determined by...
-the lifetime of the ligand-receptor complex
-the amount and lifetime of the receptor-effector protein complex
-modulation of signal response
What does arrestin do?
Binds to the receptor, preventing activation of the G-protein. Desensitizes the cell to the signal.
What is down-regulation?
Endocytosis of membrane-bound receptors.
In the cAMP pathway of signal transduction, what does cAMP do?
Activates Protein Kinase A (PKA).
What does PKA do in the cAMP pathway?
phosphorylates cytosolic proteins (turning them on), and enter nucleus to activate CREB (aAMP responsive element).
What do phosphodiesterases do?
Catalyzes cAMP to 5'AMP, ending response.
In the cAMP pathway, what is the difference between Stimulatory G-proteins, and Inhibitory G-proteins?
Simulatory G-proteins activate adanylyl cyclase. Inhibitory G-proteins turn it off.
How does Vibrio cholerae cause disease?
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.
How does Bordetella pertussis cause disease?
Pertussis toxin causes the inactivation of the G-protein. It is locked in the "inactive" state.
inositol 1,4,5-trisphosphate
phosphatidyl inositol diphosphate
How does the DAG, IP3 pathway work?
-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
What is an example of what the βγ subunit of the G-protein can activate?
-a cell membrane K+ channel
Receptor Tyrosine Kinase

(a transmembrane protein with an intracellular kinase domain and an extracellular domain that binds ligand)