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Pharmacology > S1: Receptor Mechanism I > Flashcards

S1: Receptor Mechanism I Flashcards

1
Q

What does a indigenous neurotransmitter/hormone do?

A

It occupies a receptor (affinity) and causes a response (efficacy) like a lock and key

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2
Q

What does an exogenous agonist do?

A

It will be different in shape slightly but will mimic the indogenous response

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3
Q

What are the properties of receptors?

A
  • tissue selectivity
  • chemical selectivity
  • extracellular/intracellular communication
  • amplification
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4
Q

Name the 4 different type of receptors

A

Receptors
Enzyme
Carrier molecules
Ion channels

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5
Q

What are receptors locates in plasma membrane of cells called?

A

Transmembrane proteins

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6
Q

How do transmembrane proteins communicate information to cells?

A

They are different receptor groups that bind drugs at external sites to communicate distinct types of information to the cell

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7
Q

What are the 4 classifications of receptor families?

A

Ligand gated receptors
G protein-coupled receptors
Tyrosine kinase receptors
Intracellular receptors

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8
Q

How many protein subunits are ligand gated receptors made of?

A

5

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9
Q

How many transmembrane regions (membrane spanning protein domain) does one protein subunit in a ligand gated receptor have?

A

4

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10
Q

How many transmembrane regions are ligand gated receptors made of?

A

20

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11
Q

What is the extra cellular site where a ligand binds to in a ligand gated receptor called?

A

N- terminal region

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12
Q

Explain the signal transduction mechanism of ligand gated receptors

A
  1. Ligand binds to receptor
  2. Conformational change in subunits
  3. Ion channel opens
  4. Increase in ion flux
  5. Change in cell excitability- more positive inside the cell causing depolarisation
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13
Q

What is conformation change?

A

A change in shape of a macromolecule

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14
Q

Examples of Ligand gated receptor

A

Nicotinic: controlling skeletal muscle contraction
Glutamate: controlling AP firing in brain

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15
Q

How many proteins is G protein coupled receptors made of?

A

1 protein

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16
Q

How many transmembrane regions does G protein coupled receptors have?

A

7 transmembrane regions (1 protein spans the membrane 7 times)

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17
Q

What is the ligand binding site on G protein coupled receptors called?

A

N terminal

18
Q

What is the C terminal on G protein coupled receptors?

A

G protein binding region

19
Q

Explain the signal transduction mechanism of G protein coupled receptors

A
  1. Ligand binds to receptor
  2. Conformational change in receptor
  3. Activation of G proteins
  4. Production of intracellular messengers
  5. Cellular function
20
Q

Compare the speed of G protein coupled receptors to ligand gated receptors

A

G proteins are slower taking second to minutes due to the fact that messengers need to be produced

Ligand gated receptors are very fast responses that occur on the millisecond (ms) timescale.

21
Q

Explain how G protein work when drug binds to receptor

A
  1. When no drug is bound, G protein is bound to receptor. GDP is bound to the a subunit at rest.
  2. The drug binds
  3. Change in receptor conformation
  4. Now GTP is bound to Ga subunit - this is because GTP has much higher affinity to the new shape of receptor so removes GDP
  5. Ga subunit dissociates from receptor and induces a cellular response
  6. Intrinsic Ga subunit GTPase activity- GTP dephosphorylates to GDP
  7. G-protein a B y subunits reassociate and bind with unbound receptor
22
Q

What do the B and y subunits in G protein do?

A

They tether the G protein to receptor and to the membrane

23
Q

What does the a subunit in G protein do?

A

It detaches and goes off and activates the mechanism that leads to intracellular messengers

24
Q

What does the a subunit in G protein do?

A

It detaches and goes off and activates the mechanism that leads to the production of intracellular messengers

25
Q

Give three examples of the type of a subunit

A

The type of a subunit determine which systems inside cell are activated
Gas (stimulatory)
Gai (inhibitory)
Gaq

Different a subunits interact with specific targets

26
Q

Explain the GaS mediated pathway

A

Gas stimulates adenylate cyclase (AC) and converts ATP into cyclic AMP (cAMP). This increases cAMP levels which stimulates protein kinase A (PKA)

27
Q

Explain the Gai mediated pathway

A

Gai inhibits adenylate cyclase (AC) and uses ATP to decrease cyclic AMP (cAMP) levels. This inhibits protein kinase A (PKA)

28
Q

Explain the Gaq mediated pathway

A

Gaq binds to phospholipase C (PLC) which converts PIP2 into IP3 and DAG.

  • IP3 binds to IP3 receptors on the SR membrane which opens a calcium channel that increases concentration of cytosolic calcium levels
  • DAG activates protein kinase C (PKC)
    This can increase the permeability of ion channels
29
Q

Activation of G protein couples receptors regulate many biological processes

Give examples

A

Enzyme, transporters
Contractile proteins
Gene expression
Ion channels

30
Q

Explain the structure of a tyrosine kinase receptor

A
  • Monomer
  • 1 single protein subunit
  • 1 transmembrane domain
  • N terminal is extracellular: Bind ligand
  • C terminal is intracellular: Binds effector
31
Q

Where are tyrosine kinase receptors found?

A

Areas of growth factors, cytokines, hormones

32
Q

Explain the signal transduction mechanism of tyrosine kinase receptors

A
  1. Ligand binding to monomers induces dimerisation
  2. Monomers phosphorylate tyrosine residue in each another
  3. Phosphorylated intracellular domains bind enzymes/other cellular proteins
  4. Cellular function
33
Q

What is the speed of response of tyrosine kinase?

A

Slow response that can take minutes, hours, days

34
Q

Give an example of a tyrosine kinase receptor

A

Insulin receptor

35
Q

Where are intracellular (nuclear) receptors found?

A

Within the cytoplasm of the cell

36
Q

What is the structure of intracellular (nuclear) receptors?

A

Monomer - 1 single protein subunit

  • DNA binding side
  • N terminal: binds heat shock protein (HSP) and agonist
  • C terminal: Controls transcription
37
Q

What is the main function of intracellular (nuclear) receptors?

A

Regulates gene transcription

38
Q

Explain the signal transduction mechanism of intracellular (nuclear) receptors

A
  1. Drug crosses the plasma membrane (lipophilic)
  2. Hormone (drug) displaces HSP and therefore binds to N-terminal
  3. Hormone/receptor complex enters nucleus and binds to hormone responsive element on a gene DNA binding site
  4. Modulation of gene transcription
39
Q

What is the speed of intracellular (nuclear) receptors?

A

Slow response

Hours, days, months and beyond

40
Q

Glucocorticoids are very important anti inflammatory drugs (hormone)

What is the cellular mechanism of glucocorticoids?

A
  • Glucocorticoid get inside cell and binds to receptor (GCR) and dissociates HSP
  • Glucocorticoid/GCR complex is translocated to the nucleus
  • Expression of genes can be increased or decreased (e.g. processes involved in inflammation are down regulated)
41
Q

Name the excitatory muscuranic receptors

A

M1 M3 M5

They take the Gaq pathway where they activate Phospholipase C

42
Q

Name the inhibitory muscuranic receptors

A

M2 M4

They take the Gai pathway where they inhibit adenylate cyclase

Pharmacology (13 decks)

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