Overview of types of receptors, their mechanisms of action and examples

Overview of types of receptors, their mechanisms of action and examples

Main types of drug targets and their mechanisms of action

Drug Target




Channel-linked receptors

Coupled directly to an ion channel. Activation opens the channel, making a cell membrane permeable to specific ions. These channels are known as ‘ligand-gated’ because it is receptor binding that operates them (in contrast to ‘voltage-gated’ channels that respond to changes in membrane potential) (see B in figure).

Nicotinic acetylcholine receptors;

gamma-Aminobutyric acid (GABA) receptors

G-Protein coupled receptors

Coupled to intracellular effector mechanisms via a family of closely related 'G‐proteins' that participate in signal transduction by coupling receptor binding to intracellular enzyme activation or the opening of an ion channel. Secondary messenger systems include the enzymes, adenylyl cyclase and guanylyl cyclase, which generate cyclic AMP and cyclic GMP, respectively (see A in figure).

Muscarinic acetylcholine receptors;


Dopamine receptors;

5-hydroxytryptamine (Serotonin) receptors;

Opioid receptors


Kinase-linked receptors

Linked directly to an intracellular protein kinase that triggers a cascade of phosphorylation reactions.

Insulin receptors

Nuclear hormone receptors

Intracellular and also known as 'nuclear receptors’. Binding of a ligand promotes or inhibits synthesis of new proteins, which may take hours or days to promote a biological effect.

Steroid hormone receptors;

Thyroid hormone receptors;

Vitamin D receptors

Other targets

Voltage-sensitive ion channels

Found in excitable tissues and a potential target for drugs that can block the channel or interfere with conductance in other ways.

Na+ channels that are blocked by local anesthetics such as lidocaine


Catalyze biochemical reactions, some of which involve the production of key mediators of physiological processes in body systems. Drugs interfere with the active site of the enzyme or affect co‐factors required by the enzyme for activity. In most cases inhibition of the active site is competitive although in some cases it may be long-lasting and effectively irreversible (e.g. aspirin) (see C in figure)

Inhibitors of cyclooxygenase such as aspirin;

Inhibitors of angiotensin converting enzyme such as  enalapril;

Inhibitors of xanthine oxidase such as allopurinol

Transporter proteins

Specialized proteins that carry ions or molecules across cell membranes. Movement may be in either direction, and may involve exchange of one substance for another, co-transport of two or more substances in the same direction, or ‘pumping’ of a single substance into or out of a cell or organelle. Drugs may act on transporters to inhibit their activity or may also act as ‘false substrates’, preventing the transport of the normal biological substrate (see D in figure).

Inhibitors of serotonin reuptake transporter such as fluoxetine

Cell adhesion proteins

Type-1 membrane glycoproteins that mediate cell-cell and cell-matrix adhesion by acting as transmembrane linkers to connect ligands on the outside of the cell (other cell membrane molecules, ECM components) to the actin cytoskeleton. Includes the adherins and integrins.

β2 integrins on leukocytes which are essential for effective immune responses. Adhesion class GPCRs. Cadherins such as E-cadherin required for endothelial cell-cell contact, and tissue morphogenesis during embryonic development.

Drug receptor interactions

MSD Manual for the Professional (formerly Merck's Manual)

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