Beta-2 adrenergic receptor

Beta-2 adrenergic receptor (β2 adrenoreceptor), also known as ADRB2, is a G protein-coupled receptor (GPCR) that interacts with epinephrine, a hormone and neurotransmitter, to trigger a range of physiological responses. These responses primarily involve the relaxation of smooth muscles in the airways and vasodilation in skeletal muscle and liver. The β2 adrenergic receptor is encoded by the ADRB2 gene in humans.

Structure

The β2 adrenergic receptor is a member of the GPCR superfamily and shares a common structure with other members: seven transmembrane alpha helices, an extracellular N-terminus, and an intracellular C-terminus. The receptor is embedded in the cell membrane, allowing it to interact with epinephrine in the extracellular space and G proteins within the cell.

Function

The primary function of the β2 adrenergic receptor is to mediate the effects of epinephrine and norepinephrine in a variety of tissues. Activation of the receptor leads to a cascade of events that promote muscle relaxation, particularly in the bronchi, leading to bronchodilation. This is crucial in the management of asthma and COPD, where β2 agonists are used as bronchodilators.

In the cardiovascular system, β2 activation results in vasodilation, which can help to lower blood pressure. In the liver, it stimulates glycogenolysis, the breakdown of glycogen to glucose, increasing blood glucose levels and providing energy to muscles during acute stress.

Clinical Significance

Mutations in the ADRB2 gene can affect the function of the receptor and have been linked to a variety of diseases, including asthma, obesity, and hypertension. Polymorphisms in the gene can influence the response to β2 agonist drugs, which are commonly used in the treatment of asthma and COPD.

Pharmacology

β2 adrenergic receptors are the target of several pharmacological agents, including: - β2 agonists (e.g., salbutamol, also known as albuterol in the US), which are used primarily for the treatment of asthma and COPD by causing bronchodilation. - β blockers (e.g., propranolol), which can inhibit the action of β2 adrenergic receptors, are used in the treatment of hypertension, though they primarily target β1 receptors.

Research Directions

Research into β2 adrenergic receptor has focused on understanding its role in disease and developing new therapeutic agents that can target this receptor more effectively. This includes the development of ultra-long-acting β2 agonists for asthma and COPD treatment and exploring the receptor's role in metabolic diseases and cardiovascular health.

See Also

• G protein-coupled receptor
• Epinephrine
• Asthma
• Chronic obstructive pulmonary disease (COPD)
• Beta-2 agonist
• Beta blocker