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pharmacology > drug receptor > Flashcards

drug receptor Flashcards

1
Q

what are the 4 main receptor classes/types

A
  1. ligand gated ion channels
  2. g coupled protein receptor
  3. enzymes linked receptor/ kinase linked receptor
  4. nuclear receptor
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2
Q

what is the structure of ligand gated ion channels

A
  • consists of 4/5 subunits making a cylinder/helical structure
  • binding of ligand to the orthosteric site opens ion channel allows the flow or one or a few ions (na, k, ca or cl)
  • can cause depolarisation or hyperpolarisation of membrane
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3
Q

what is the speed of transmission in ligand gated ion channels

A

milli seconds

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4
Q

what are three examples of ligand gated ion channels

A
  • nicotinic cholinergic
  • GABA-A
  • 5HT3
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5
Q

what are examples of other ion channels that drugs target which are not ligand gated receptors

A
  • voltage gate ion channels which are specific to one ion examples include
  • calcium voltage gated ion channels, amlodipine (calcium channel blockers) targets these and help with angina and hypertension
  • sodium voltage gated ion Chanels, amiodrone (sodium ion channel blockers) targets these and help with heart irregularities
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6
Q

what is the most common receptor for drug target and what percentage of drugs target these receptors

A
  • GPCR
  • 30%
  • over 856 gpcr’s
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7
Q

what is the structure of GPCRs

A
  • has an extracellular N terminus
  • transmembrane 7 alpha helical domains
  • intracellular c terminus
  • associated with a G protein - intracellularly
  • G proteins - made of 3 subunits an alpha, beta, gamma
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8
Q

what is the different types of G proteins

A
  1. Gs- activation of this G protein results in activation of adenylate cyclase this results in more cyclic AMP being produced (secondary messenger)
  2. Gi/o- inhibits adenylate cyclase so less cAMP
  3. Gq/11- stimulated phospholipase c so more IP3 and DAG (secondary messenger)
  4. Go- negatively regulates adenylate cyclase and positivity regulated phospholipase c
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9
Q

what happens when a ligand/agonist binds to GPCR

A
  • the GTP bound to the alpha subunit is replaced by GDP
  • alpha subunit separates from beta/gamma subunit
  • downstream signalling molecules activated
  • secondary messenger formed e.g. cAMP
  • also note one gpcr can bind to more than one type of g protein and therefore more that one type of secondary messenger be formed resulting in more that one outcome/effect
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10
Q

what is the transmission of GPCR

A
  • SECONDS
  • Due to secondary messenger needing to be formed
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11
Q

what is the transmission of enzyme linked/ kinase linked receptors

A

hours

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12
Q

what is an example of a gpcr

A

muscarinic choligernic

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13
Q

how can enzyme linked receptors be divided into

A
  • many types of enzyme linked receptors
  • e.g. cytokine receptors
  • tyrosine kinase linked receptors
  • serine kinases
  • toll like receptors
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14
Q

what is the structure of tyrosine kinase linked receptors

A
  • has an extracellular ligand binding domain
  • transmembrane region
  • intracellular kinase domain
  • single membrane
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15
Q

what does kinase linked receptors respond to

A
  • respond to growth factors and indirectly regulate gene expression
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16
Q

what happens when agonist/ligand bind to tyrosine kinase linked receptor

A
  • tyrosine kinase receptor dimerizes
  • tyrosine residues undergo autophosphorylation
  • creates binding sites for certain proteins such as Grb2
  • causes phosphorylation of the protein
  • activates ras and the cycle goes on - kinase cascade
17
Q

what are cytokine receptors

A
  • don’t have an intracellular kinase domain
  • but are associated with a tyrosine kinase so when a ligand bind this tyrosine kinase is activated (JAK)
  • bind specifically to cytokines and are often dimeric
18
Q

what are some examples of tyrosine kinase receptors and the drugs which target it

A
  • HER2 is a tyrosine kinase linked receptor and are targeted by trastuzumab which are monoclonal antibodies used to treat breast cancer
  • insulin receptors are tyrosine kinase linked receptors (exist as a dimer- held by disulphide bridges)
  • imatinib are cancer drugs which target tyrosine kinase linked receptors
19
Q

what are the structure of nuclear receptors

A
  • soluble protein present in cytoplasm and sometimes nucleus
  • ligand activates transcription factors
  • bind to DNA once activated
  • usually homo or hetero dimer
  • 3 domains a dna binding domain, ligand binding domain, activation function domain
20
Q

what are the two types of nuclear receptors

A

-steroid receptors (oestrogen) which are usually found in the cytoplasm bound to a protein such as heart shock proteins
- PPARs where there’s 3 types (alpha, beta and gamma)
- alpha has roles in homeostasis, gamma has roles in insulin sensitisation, beta has roles in fatty acid metabolism
- PPARs mostly reside in nucleus

21
Q

what is the transmission time for nuclear receptors

A

hours

22
Q

what drug targets PPARy (nuclear receptors)

A

pioglitazone acta as an agonist for PPARy
used as a treatment for diabetes type 2

23
Q

what drugs target estrogen receptors (steroid- nuclear)

A

ethinylestradiol
- used in contraceptive pill etc

24
Q

what is another words for GPCR

A

metabotropic receptors

25
Q

what is another word for ligand gated ion channels

A
  • ionotropic

pharmacology (4 decks)

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