concepts of agonist and antagonist receptors
TRANSCRIPT
Concept of agonists and antagonists in receptor activation and inhibition and significance in regulation of signaling.
BY – RAHUL KUMARM.Sc. LIFE SCIENCE3RD SEMESTERCUG/2014/1073
Objective: Ligand & its types
Agonist & Antagonist
Properties & Types of Agonist
Properties & Types of Antagonist
Significance in regulation of signaling
Classification of ligands:
• Ligands are classified by effect upon binding to the receptor. LIGANDS
Agonist
Antagonist
Comparison between agonist & antagonist: Agonist
• Derived from Latin word – contender.
• Aids in the enhancement of an action.
Antagonist
• Derived from Latin & Greek words – competitor or opponent.
• Opposes the action of agonist and block the reception.
Receptors can be activated either by endogenous or exogenous , leads to change in the biological response.
Types of agonist- a) Full agonist b) Partial agonist c) Inverse agonist
Full agonist – The ligands that increase the activity of the receptors & produce the maximal response . Ex.- Morphine ,mimics the action of endorphins at opioid receptors.
Partial agonist – These ligands partially increase the activity of the receptors but do not produce the maximal response like full agonist even when present in excess amount. Ex.- Buspirone , is an anxiolytic drugs , used to treat an anxiety disorder.
Inverse agonist – The ligands which decrease the activity of an active receptors to their inactive state. Ex.- Flumazenil drugs acts as a inverse agonist for the GABA receptor & produce anxiogenic effect.
Properties of Antagonist : Site selectivity. Structural conformation – mimics with the natural ligand.
Reduces the response.
Effect may be temporary or permanent.
Competitive antagonists – The antagonist competes with the agonist for the orthosteric sites for binding to the same receptor . - The effect of the antagonist can be overcome by increasing the concentration of the agonist.
Ex.- IL-1RA protein competes with IL-1 for binding to the cell surface interleukin-1 receptor.
Non-competitive antagonists : The antagonist binds at a different site other than orthosteric site on the receptor. - The effect of the antagonist cannot be overcome by increasing the concentration of agonist. Ex.- Binding of cyclothiazide with mGLUR1 receptor.
Irreversible antagonists: May or may not competes with the agonist for orthosteric sites for binding to the receptor. - Forms covalent bond to the site.
Ex.- Aspirin.
REFERENCES - The cell (5th Edition) Cooper & Hausman Lehninger principle of biochemistry (5th Edition) Principles & Techniques of Biochemistry & Molecular biology (7th Edition) by Kleith Wilson & John Walker Handbook of cell signaling Vol.1 (2nd Edition)