Molecular pharmacology Flashcards Preview

BIOL2049 S1 > Molecular pharmacology > Flashcards

Flashcards in Molecular pharmacology Deck (46)
Loading flashcards...
1
Q

Learning objectives

A
  • Introduce the idea of receptor families.
  • Describe how gene cloning and most recently genome sequencing have expanded view of receptor families.
  • Describe some of the better characterized receptor families and list aspects of their structure function activity.
  • Use GPCR adrenergic receptor and nicotinic acetylcholine receptors to detail how current and emerging structures inform on protein conformations that allow receptor function.
  • Describe principles of tyrosine kinases and steroid receptors.
  • Introduce the key principles Pharmacogenomics.
  • Use examples of how genetic determinants effect drugs by changing their Pharmacokinetics and Pharmacodynamics.
2
Q

When listing the major receptor families, how can you group them by?

A
  • Molecular characteristics
  • Major drugs-indicating affinities, efficacies, and relative specificities
  • Good for revising and drug related write ups
3
Q

What are the two classifications of receptor families?

A
  • Anatomical classification
  • Pharmacological classification
4
Q

Are adrenaline and noradrenaline shown to have a wide range of effects?

A

yes

5
Q

Whats are the anatomical classifications of drugs?

A

Different vessels gave distinct response constrict or dilate

6
Q

What are some pharmacological classifications of drugs?

A
  • Ahlquist noted a rank order of potency for adrenergic agonists depending on the nature of the response.
  • Constricting responses: Noradrenalin>adrenalin>isoprenaline
  • *ALPHA RECEPTOR**
  • Dilating responses: Isoprenaline>adrenalin> noradrenalin

BETA RECEPTOR

7
Q

Differential pharmacology (structure function) and receptor associated signalling

A
  • Known to activate the alpha- and beta-adrenergic beta responses
  • Build up better idea of underlying receptor
    • means no response on the drug
  • Shows to distinct alpha and beta receptors
  • Propranolol blocks all beta responses
  • Pindolol only blocks the beta 1 responses
8
Q

Tell me about molecular classification and receptor family expansion through gene cloning

A
  • Identify and sequence the cDNA for the receptor.
  • Predicts the amino acid sequence of the receptor.
  • Repeat for all receptor sub-types compare amino acid to give a molecular classification.
  • Often leads to identification of distinct sub-types not realized by pharmacological classification.
9
Q

Methods that reveal molecular basis of receptor sub-types

A
10
Q

Tell me about molecular methods that open up diversity in receptor families

A
  • Hybridise under high temperatures as they are identical much like DNA
  • Homologous indicate different but related proteins. Would hybridise under lower temperatures
11
Q

Molecular methods that open up diversity in receptor families

A
12
Q

What is genomic DNA made up of and what are each of these components?

A
  • Genomic DNA is made of DNA sequence
  • DNA sequence is the introns and exons
  • Exons are part of genomic DNA that go onto make mRNA that encodes the protein
  • Exons come together to make up coding sequence
  • Exons interrupted by introns, would remove and splice introns in order to make proteins
13
Q

How can a computer be used for genomic sequencing?

A
  • Computer can remove introns to get exons. Predict by splicing on computer
  • Predicted mRNA could look similar would be extinct from those already existing
14
Q

What does homology mean?

A

the state of having the same or similar relation, relative position or structure

15
Q

What is cDNA?

A

cDNA meaning complementary DNA (synthetic DNA in which the sequence of bases is complementary to that of DNA)

16
Q

How do you build post-genomic receptor families?

A
17
Q

How much of the human genome encodes the G-protein coupled receptors?

A

3-5% of genes

estimate 30,000 genes in the genome >1000 G-protein receptors

18
Q

Tell me about the families in the G-protein receptor super family?

A

There are 5 families in the G-protein super family, they have 2 different names:

Family 1= rhodopsin family (different names for same thing)

Family 2= secretin family

Family 3= Glutamate family

Family 4= Frizzled/ TAS2 family

Family 5= adhesion family

19
Q

Using family 1 of the G-protein super family as an example, tell me the sub-types of the superfamily

A
  • Sub types of the super family using family 1 as an example
  • But a subclassification of the superfamily and all the layers
  • Alpha 1, alpha 2, beta 1, beta 2, beta 3 (what the starts of the sub-class represent)
20
Q

Tell me the different effects that adrenaline/ noradrenaline can have an on what receptor they have to act on for this affect

A
21
Q

Tell me about what drugs act on receptors and in what tissues for certain clinical uses…

A
22
Q

Tell me about receptor signalling in a cDNA and a mutated cDNA

A
23
Q

Whats some useful information for structure function studies?

A
24
Q

Tell me about structure function studies?

A
  • These are used to help understand receptor transduction
  • 4 ways in which the receptor can be stimulated and the way it can come in via 4 different channels e.g. GPCR, ligand gated ion channels, tyrosine kinases, steroid receptors
25
Q

What do the G-proteins that associate with GPCRs have?

A

They are heterotrimeric meaning they have 3 different subunits: alpha, beta and gamma

alpha and gamma are attached to the plasma membrane by lipid anchors

26
Q

How does the alpha subunit exchange on G proteins exchange GDP for GTP?

A
  • When GDP is bound to the alpha subunit, the alpha subunit remains bound to the beta-gamma subunit to form an inactive trimeric protein
  • This conformational change causes the alpha subunit to give up its GDP in exchange for GTP
  • Once bound to GTP, the alpha subunit dissociates from the beta-gamma complex.
27
Q

Tell me the primary, secondary, tertiary and quaternary structure of the GPCR?

A
  • Primary structure: Multifaceted family made up related sub-families (see previous lecture)
  • Secondary structure: all receptors predicted to be seven transmembrane spanning
  • Tertiary structure: Rhodopsin and many structures support the 7 transmembrane model.
  • Quaternary structure: growing evidence that some GPCR may operate as dimers of individual subunits (e.g., Family 3).
28
Q

Tell me about transduction of GPCRs?

A
  • Bind agonist supplied from outside
  • Alter receptor conformation
  • Make contact to activate G-protein
29
Q

Tell me about the secondary structure of an adrenergic GPCR?

A
30
Q

Tell me about adrenergic agonist binding sites in transmembrane domains

A
31
Q

Tell me about the important aspects of the agonist binding site and the conformational changes to fully activate?

A
  • Agonist binds moves helices (5 and 6) creates a G-protein binding site.
  • Poor activation of the receptor if G-protein does not bind.
  • Agonist bind moves helices (5 and 6) G-protein binds stabilizes change in helices conformation.
  • Suggests interdependence of the agonist, binding transmembrane conformation and
  • G-protein binding.
32
Q

Give an example of a ligand-gated ion channel

A

Nicotinic Acetyl Receptor super-family

33
Q

Tell me about the primary structure of ligand gated ion channels

A

Primary structures

  • A number of related genes encoding sub-units that make up distinct members of this family.
  • Acetylcholine (Nicotinic) and 5-HT (5-HT3) excite allowing Na+ to flow in
  • Glycine and GABA inhibit by allowing Cl- to flow in
34
Q

Tell me about the secondary structure of the ligand-gated ion channels?

A

Secondary structure

Each subunit exhibit a common and distinct shared trans-membrane topology.

35
Q

Tell me about the Tertiary structure of the ligand-gated ion channels?

A

Tertiary structure

good models of tertiary structure are now supported by structural information for whole receptor or domains of the receptor.

36
Q

Tell me about the quaternary structure of the ligand gated ion channels

A

Quaternary structure

exist as oligomeric receptors made up of a mix and match of individual subunits. 5 subunits associate to generate a PENTAMERIC functional receptor

37
Q

For fast and self-contained ligand gated ion channels whats the transduction mechanism?

A
  • Bind agonist from the outside
  • Conformational change or gate of ion channel
  • Select specific ions to flux through ion channel
  • pass through membrane.
  • Operate on a millisecond time scale
38
Q

Tell me the key features of the nicotinic acetylcholine ligand gated ion channel superfamily

A
39
Q

What do protein alignments reveal and what does this mean?

A
  • The protein alignments reveal ancient nicotinic receptor superfamily like proteins in bacteria
  • This means it is easier to overexpress the protein and produce large amounts for structural studies
40
Q

Where is the acetylcholine binding site?

A

Acetylcholine binding site is at the alpha subunit and on neighbouring non-alpha subunit

41
Q

Tell me about the organisation and key features of the M2 ion channel domain?

A
  • Twisting the hydrophobic residues in M2 helix could open the ion channel but would twist the aligned hydroxyl residues (so nice idea that probably wrong)!
  • Amino acid alignment that is generally conserved in M2 of this receptor family. Charged residues (-2), hydroxyl residues 2 and 4 and hydrophobic residues (9 13 16) co-ordination, selectivity and flux.
42
Q

What moves the M2 ion channel lining helix so it opens receptor ?

A
  • Twisting the agonist binding site and levering the underlying ion channel moves the M2 ion channel lining helix so it opens receptor
  • Rotation in an individual subunit co-ordinated across subunits of oligomeric protein increases the size of the ion channel thus it opens.
43
Q

Tell me about the 1˚, 2˚, 3˚ and 4˚ structure of the tyrosine-kinase linked receptors

A
  • Primary structure A number of different growth factor receptor gene families
  • (e.g., NGF, cytokines and Insulin receptors same basic transduction pathway)
  • Secondary structure Single transmembrane spanning or membrane associated domain.
  • Tertiary structure. Isolated ligand binding domain or kinase domains confirm likely structures.
  • Quaternary Clear dimerization required during signal transduction and some exist as oligomers before ligand
44
Q

Tell me the transduction mechanism of the tyrosine-kinase linked receptors

A
  • Activate by extracellular ligand
  • Conformational change drives receptor dimerization
  • Dimerization activates intrinsic tyrosine kinase or recruits
  • non membrane associated kinase
  • Creates site for phosphotyrosine or SH2 binding sites
45
Q

Tell me about steroid receptors

A
  • Cholesterol starting point for synthesis of mineralocorticoids (aldosterone), glucocorticoids (corticosterone) and sex steroids (e.g., oestrogens).
  • Lipid soluble, diffuse into the cell and act on intracellular receptors.
46
Q

Tell me the transduction mechanism of the steroid receptors

A
  • Diffuse into cell and nucleus and bind Hsp-90 inactivated receptor.
  • Dissociate HSP-90 and dimerize to give active form of the receptor.
  • Activate transcription