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37 Cards in this Set
- Front
- Back
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What are the 3 types of membrane receptors?
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1. Ion channel linked (ionotropic)
2. GPCR (metabotropic) 3. Enzyme-linked |
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What are 4 important characteristics of Ion channel-linked receptors?
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1. It is a common gene family
2. The receptor directly gates an ion channel 3. These are major drug targets 4. Allows for RAPID signalling |
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What are the 2 major ionotropic receptors?
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-Nicotinic ACh receptors
-GABA receptor gated Cl channels |
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What is GABA?
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Gamma-aminobutyric acid
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What is the nicotinic ACh receptor a channel for?
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Pos cations - Na/K
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What is the response of the cell when ACh binds to the nicotinic cholinergic ionotropic receptor?
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Excitation - Depolarization
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At what 3 sites is the nicotinic ACh receptor located?
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-NMJ
-Autonomic PNS -CNS |
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What is the GABA receptor an ion channel for?
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Chloride
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What is the cell response when GABA binds its receptor?
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Hyperpolerization so Inhibition
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Where is GABA found operating on these GABA receptors?
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CNS
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What is GABA then?
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The main post synaptic inhibitory neurotransmitter in the CNS
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What are 2 drugs that act via increasing the sensitivity of the GABA receptor? How do they work?
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-Benzodiazepines
-Barbiturates -Allow lower concentrations of GABA to open the channel |
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What is the main general feature of the GPCR?
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It is a multi component system!
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How many GPCRs are there in the large family of them?
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~1000
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What are 5 effects mediated by GPCRs?
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-Neurotransmitters
-Light -Oderants -Hormones -Other extracellular messengers like growth factors and cytokines |
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What makes up the receptor component of GPCRs?
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A single 7-transmembrane protein
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To what is the 7-TM protein coupled?
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Heterotrimeric G proteins
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What is a heterotrimeric G protein?
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A Guanine nucleotide binding protein that links the ligand-activated GPCR to effector enzymes
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So for the GPCR complex
-What provides specificity? -What does the transducing? -What is the effector? |
Specificity = 7TM receptor
Transducer = G-protein Effector = the catalytic component that generates a 2nd messenger |
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How do Heterotrimeric G-proteins exist?
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As molecular switches that cycle between two states
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What are the 2 states that G-proteins cycle between?
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Active - GTP bound
Inactive - GDP bound |
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What do Heterotrimeric G proteins consist of?
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3 proteins (subunits)
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What are the 3 subunits that G proteins are composed of?
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-G alpha
-G beta -G gamma |
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What is the function of Ga?
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Binds GTP/GDP, functions as a GTPase
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What is the function of GB-Gy?
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-Membrane anchor
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How are heterotrimeric G proteins classified?
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According to the type of G-a that is present in the trimer
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What does Ga-s do?
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Stimulates adenylate cyclase which activates PKA
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What does Ga-i do?
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Inhibits adenylate cyclase which inactivates PKA
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What does Gaq do?
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Activates phospholipase C which turns on PKC
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What is the general feature to know about Enzyme-linked receptors?
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They are a diverse group of receptors with different enzymatic activities.
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What is the most important enzyme-linked receptor?
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Tyrosine Kinase linked Receptors
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What happens when ligand binds to a TKLR?
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Dimerization
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What follows dimerization of a TKLR?
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Acivation by crossphosphorylation (auto) of the internal domains
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What follows autophorphorylation of the cytoplasmic domains?
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Intracellular signaling molecules bind
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What gets regulated by the intracellular signalling molecules?
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Cell proliferation and differentiation
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What 3 ligand types utilize TKLRs to regulate cell proliferation and differentiation?
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-Hormones
-Growth factors -Cytokines |
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What disease process do TKLRs play an important role in?
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Oncogenesis
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