Module 1 Flashcards
Pre-scientific era: what remedies were used, where were they obtained, and what was the knowledge for them?
Morphine, aspirin, alcohol, cocaine
Natural sources
- Mechanisms unknown
- Side effects not widely recognised
- Structure of the drug and target is unknown
Cocaine in the 19th century: how accessible was it, was it understood, and where was it used?
Uncontrolled, available from grocery stores
Mechanism not understood
Included in patent medicines
What was cocaine used to treat?
Freud said:
- Mental stimulant
- Treatment for digestive
- Disorders
- Appetite stimulant
- Treatment for morphine addiction
- Treatment for asthma
- Aphrodisiac
- Local anaesthetic
The regulation of cocaine as an anaesthetic throughout time
Early 1900s: regulation
- Procaine synthesised 1905 (Einhorn)
- Tetracaine 1941
- Lidocaine 1943
(Cocaine still used though)
What did Paul Ehrlich research and what synthetic drug did he make?
- Research on sleeping sickness
- Tested >900 arsenical compounds
- 1909 #606 tested on syphilis
- Completely effective
- Released 1910: Salvarsan
The three ways that drugs can be discovered
Natural sources (Cocaine, Aspirin)
Synthetically produced (Salvarsan)
Serenpidity (Penicillin)
Pharmacology, pharmacodynamics, and pharmacokinetics: what do they all mean?
- Actions of drugs on living organisms
- The mechanisms of drug action
- The handling of drugs by body use of drugs as scientific tools (?)
What do drugs target and what are the examples of the exceptions?
Proteins
Exceptions:
* Antacids
* Osmotic diuretics (reduce intracranial pressure)
* DNA modifying drugs (cancer therapy)
* Drugs that target membrane lipids (some antibiotics)
Interactions with the exceptions tend to be non-saturable, with little specificity
Relative sizes of drugs and receptors
Drugs are usually quite small (<500 Da) in comparison to the receptors (100s of kDa)
This general rule does not apply to protein-based drugs like monoclonal antibodies
Drug binding domains: what are they, and what issues may arise if mutations occur in this area?
The cavity in the receptor which allows things (like drugs) to bind given that they can attach to and cope with the chemical environment caused by its amino acids
If a mutation occurs affecting only the binding domain, then the general shape and structure of the receptor may be the same, but drugs (and other binders) may not be able to bind and so that function is lost
What does the binding energy of a drug binding to a protein do?
When the drug binds to a receptor, the binding energy released will either be stabilised in a particular conformation or may cause a conformational change
The conformational change of the protein causes the drug’s effect
Protein superfamilies: what are they and what causes their grouping?
Massive groups containing large amounts of proteins
These are grouped together based on similar structure, function, and gene sequence
CNS, muscle, heart, and DRG: what can mutations to sodium channels in these areas cause?
CNS: epilepsy
Muscle: myotonia, paralysis
Heart: rhythm disorders
DRG: insensitivity to pain, chronic pain, or psychological disorders
Target diversity: what is it and how can it be exploited?
Target diversity is an issue as some drugs may bind to two different types of proteins as some proteins are very closely related and have very similar amino acid sequences.
This can be exploited by synthetically altering drugs to not bind to any other proteins
Endogenous
Originating within the organism (hormone, neurotransmitter)
Exogenous
Originating from outside the organism (light, pressure)
Receptor: what is the definition and what are the types?
A receptor is a protein that interacts with an information-carrying stimulus and passes the information into a different form (either affecting the cell or passing the info further)
TRK, NHR, GPCRs, and LGIC
Acetylcholinesterase: is it counted as a receptor?
No, although it binds to acetylcholine, it breaks it down so it counts as an enzyme
RTK: what do they do, what do they bind to, where are they located, how many are there in the human genome, what are examples, and what are the key characteristics?
Receptor tyrosine kinase phosphorylates tyrosine residues in proteins, altering the protein’s effect and causing a specific result to occur
They bind to peptide hormones and growth factors mainly
Transmembrane
58 transmembrane proteins
Insulin receptors
- May exist as monomers but the functional unit is in a dimeric form
LGIC: what do they do, where are they located, what are examples, and what are the key characteristics?
Ligand-gated ionic channels change the membrane potential after two agonists bind to two receptor sites and open the channel
Transmembrane
Nicotinic-acetylcholine receptors
- They are all multisubunit receptors
- Can allow fast signalling
- Several structurally different types
GPCR: what do they do, where are they located, how many are there in the human genome, what are examples, and what are the key characteristics?
G-protein coupled receptors act with paired proteins (G proteins) and use these proteins to influence cell activity via other proteins
Membrane - 7 transmembrane domain structure
The biggest family of receptors - 831 genes
β₂ adrenoreceptors
- Important in olfactory, vision, and nervous system
- Act via G-proteins (cAMP/IP3/PIP₂/PLC)
NHR: what do they do, what do they bind to, where are they located, how many are there in the human genome, what are examples, and what are the key characteristics?
Nuclear hormone receptors are activated when their agonist enters the cell and binds. The NHR then binds to DNA and affects gene expression by transgression or transactivation
Lipid-soluble ligands (ie steroids)
Intracellular locations
48 receptors
Glucocorticoid receptors
- Effects tend to be slower than other receptors (hours to days)
The worldwide effect of GCPRs: how many drugs target them, what are the annual sales of their drug targets, and how many targets are there?
34% of drugs
> $180 billion
170 drug targets
Examples of conditions where drugs target GPCR and the drugs used to treat them
- Depression: Antidepressants (indirectly)
- Schizophrenia, bipolar disorder: antipsychotics (dopamine D2 receptor)
- Asthma: salbutamol (beta 2 AdR)
- Blood pressure: losartan (Cozaar), atenolol
- Glaucoma: pilocarpine (muscarinic receptors)
- Abuse: analgesics (cannabis, heroin, LSD)
The general structure of GPCRs
7 transmembrane domains
NH₂ terminus outside the cell
(Same structure of bacteriorhodospin)
Diversity of GPCR
Muscarinic receptors: M1-M5
Adrenergic receptors: α₁, α₂, β₁, and β₂
Nicotinoid acetylcholine receptors - not GPCR, VGIC
The four parts of a GPCR
- An agonist ligand
- Membrane-bound GPCR
- G-protein (guanine nucleotide-binding protein) binds to a GTP/GDP as a trimeric membrane protein
- A protein (usually an enzyme) that acts as a secondary messenger
The GPCR activation cycle
Step 1: A G-protein has a GDP attached to it
Step 2: An agonist binds to the GPCR, allowing the G-protein to attach and swap its GDP for a GTP
Step 3: The binding of GTP splits the G-protein into the α subunit with the GTP attached and the β and γ subunits
Both of these subunits will pass the message onto more target proteins
Step 4: The α subunit has GTPase so will eventually hydrolise GTP into GDP + Pi, resetting the signalling process
Why is the GPCR signalling cycle referred to as a cascade process?
One agonist gives the message to one receptor which gives the message to multiple G-proteins which give the message to a higher number of target receptors
(It’s an amplification process)
Heterotrimeric proteins
Contain an α-subunit, a βγ complex, a bound GDP, and lipids that are added post-translation
Types of α-subunits
Gi proteins:
Gᵢ/α₀, αᵢ, α₀ - inhibition of adenyl cyclase (AC)
Gₜ, αₜ (transducin) - activation PDE 6 (vision)
G₉, α₉ᵤₛₜ (gustducin) - activation PDE-6 (taste)
Gs proteins:
Gₛ, αₛ - activation of AC
Gₒₗբ, αₒₗբ - activation of AC (olfaction)
Gq proteins:
Gq, αq - activation of phospholipase C
Receptor coupled to Gs
- β-adrenoceptors
- Dopamine receptors D1 and D5
- Glucagon receptor
- Cannabinoid receptor CB2
- Histamine H2 receptor
- Luteinizing hormone receptor
- Follicle-stimulating hormone receptor
All activating/stimulating receptors
The function of Gs in the cAMP pathway
Gs gets activated by a GCPR and it swaps its GDP for a GTP which causes the α subunit to dissociate and bind to adenyl cyclase and stimulate the conversion of ATP into cAMP which binds to PKA and activates for whatever function
The function of Gi in the cAMP pathway
Gi gets activated by a GPCR and it swaps GDP for a GTP which causes the α subunit to dissociate and bind to adenyl cyclase and inhibit its action, causing less ATP to convert into cAMP, and inhibiting PKA production, reducing the effect of PKA
Receptors associated with Gi proteins
- Muscarinic acetylcholine receptors M2 and M4
- Cannabinoid receptors CB1 and CB2
- Dopamine D2, D3 and D4
- α2 adrenoceptors
- GABAB receptors
The phospholipase C pathway in activating PKC
GPCR gets activated, activating Gq (replacing its GDP with a GTP) and causing the alpha subunit to dissociate and activate phospholipase C which cleaves PIP2 into diacylglycerol (DAG) and IP3. DAG moves through the membrane and activates PKC and IP3 binds to IP3 receptors in the cytosol which release Ca²⁺ ions which bind to PKC and, with it fully activated, it can phosphorylate proteins and affect their function
Receptors associated with Gi proteins
- Muscarinic acetylcholine receptors M₁, M₃ and M₅
- Histamine H1 receptor
- Angiotensin II type 1 receptor
- α1 adrenoceptors
NHRs: what are they, what do they do, where are they found, how many of them are there, and what are the examples?
A superfamily of receptors that bind lipophilic substances (steroids etc) where their effects tend to be slower than other receptor types
Affect transcription rate of specific genes
Intracellular location (not in the membrane)
48 NHRs in man, all with a very similar structure to interact with either sex hormones or adrenal hormones (corticosteroids)
- Progesterone, oestrogen, androgen receptors
- Thyroid hormone receptor
- Glucocorticoid, mineralocorticoid receptors
- Vitamin D receptor
- Retinoic acid receptors
How do NHRs work?
Lipid soluble hormone passes through the membrane and interacts with the NHR in the cytosol, causing it to move into the nucleus where it affects the transcription rate of certain genes
NHR structure
N-terminal - DNA binding domain (DBD) - Hinge region - Ligand binding domain (LBD) - C-terminal
GCRs as NHRs (transactivation)
Glucocorticoid receptors are normally bound to heat shock proteins (HSP) but steroid interaction dissociates them and, normally, causes them to dimerize with other GCRs and enter the nucleus to interact with hormone response elements (HREs) which causes coactivator proteins to interact and increase transcription rates
Transgression
Instead of dimerising, only the monomer binds to the HRE and, since it hasn’t dimerised, transcription does not progress (ns why)
This is only one possible mechanism
Orphan receptors
NHRs/GCPRs that we do not know the function/ligand of
Ion channels: what are they, what are their significant features, and what are examples?
Pores through the membrane which allow ions to pass through
Highly selective, very fast ion movement,
GABAₐ receptor
Pumps: what are they, what are their significant features, and what are examples?
Membrane proteins which use active transport to move things through the membrane which may also manufacture ATP (ATP pumps)
Sodium-potassium ATPase
