Cell signalling by G-protein coupled receptors Flashcards
What do G-protein coupled receptors respond to?
hormones
neurotransmitters
paracrine signals
odors
light
what is the role of the receptor in the GPCR?
gives specificity
what is the role of the G-protein in the GPCR?
transduces signal
what is the role of the effector in the GPCR?
alpha and beta gamma subunits may provide different signals
what do the intracellular signals generated by effector cells often regulate?
protein kinases
what does adenylate cyclase activate?
protein kinase A (PKA)
what does phospholipase C activate?
protein kinase C (PKC)
how many pathways can a GPCR regulate?
Mulitple pathways
what is the role of protein kinases?
provide the major mechanism for changing the activity of an existing protein
what can protein kinases regulate?
-increase or reduce the activity of an enzyme
- turn a signal protein on or off
- change the location of a protein
- alter the interaction of a protein with other molecules
what is post-translational modification?
the regulated addition of a small molecule
- most often the addition of a phosphate
- adds a large negative charge
what is the result of post-translational modification?
will cause the folded protein to adjust its shape
what is phosphorylation?
transfer a phosphate from ATP to the target protein
what is the role of protein kinases?
adds phosphates
what is the role of protein phosphatases?
removes phosphates
how are protein kinases categorized?
after their amino acid target
how is protein kinase A activated?
-PKA exists as an inactive complex with its regulatory subunits
-cAMP binds to the regulatory subunits
-causes them to dissociate
-releasing the active kinase
where is inactive PKA located?
at the cell membrane
how do protein kinases increase the expression of a protein via transcription factors?
changes the amount of a specific protein in a cell
how do protein kinases change the activity of existing protein?
increase the activity of an enzyme
what is tyrosine hydrozylase?
carries out the first and rate-limiting step in catecholamine production
what are some different catecholamines?
dopamine
noradrenaline
adrenaline
where is dopamine synthesized?
in nerve terminals
when is dopamine released?
in response to nerve stimulation
how does phosphorylation effect dopamine synthesis?
phosphorylation reduces the negatibe feedback by dopamine
where can Tryosine hydroxylase be phosphorylated?
at 4 different sites
where do kinases act on tryosine hydroxylase?
different kinases act on different sites
Different sites ahve different effects on activity
-the order of phosphorylation matters
