Olfactory receptors

Question 1

Describe an approach that can be used to deorphanise olfactory receptors In vivo (organism)

Answer 1

Expose the olfactory bulb in a rat.
Apply Dil solution which is able to travel backwards to trace neurons involved.
Give the rat a certain scent, then test which GPCRs light up in recognition.

Question 2

What is the structure of an Olfactory receptor protein

Answer 2

GPCR (7TM domains)
N terminus extracellular; C terminus intracellular
Disulphide bonds between helix 3 and EL2 (between conserved cysteine residues)

Question 3

Describe how an olfactory receptor can be deorphanised using in vitro approaches

Answer 3

Clone OR receptor that is expressed by a single neuron. Amplify. Add different ligands and see what lights up. High KCl conc used as a positive control (all cells respond to it).
Can use this at different concentrations to give a dose-response curve. Shows how sensitive the receptor is to certain sub-types.

Question 4

What are the problems with an in vitro approach to deorphanise olfactory receptors

Answer 4

Activator ligands may not be available/sythesised
Specific ligands in similar cells may not have the same effect on the target OR.
Odorants are delivered to an OR through the air. This may not equate to lab odorants delivered in solution