Beta-2 adrenergic receptors

Beta-2 adrenergic receptor
Identifiers
Symbol	ADRB2
NCBI gene	154
HGNC	1097
OMIM	109690
RefSeq	NM_000024
UniProt	P07550
Other data
Locus	Chr. 5 q31-32
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The Beta-2 adrenergic receptor (ADRB2) is a type of G protein-coupled receptor (GPCR) that is primarily involved in the smooth muscle relaxation and bronchodilation processes in the human body. It is one of the adrenergic receptors and responds to the epinephrine and norepinephrine neurotransmitters in the sympathetic nervous system.

Structure

The Beta-2 adrenergic receptor is encoded by the ADRB2 gene located on chromosome 5q31-32. It consists of a single polypeptide chain that spans the cell membrane seven times, characteristic of GPCRs. The receptor's structure allows it to interact with G proteins (G_s) inside the cell, initiating a cascade of intracellular events.

Function

Upon activation by its ligands, epinephrine or norepinephrine, the Beta-2 adrenergic receptor causes a reduction in intracellular calcium levels and an increase in cAMP (cyclic Adenosine Monophosphate), which in turn activates protein kinase A (PKA). PKA then phosphorylates various target proteins, leading to smooth muscle relaxation and vasodilation. This mechanism is particularly important in the lungs, where it contributes to bronchodilation, making it a critical target in the treatment of asthma and COPD (Chronic Obstructive Pulmonary Disease).

Clinical Significance

Beta-2 adrenergic receptors are the pharmacological target of Beta-2 agonists, such as salbutamol (albuterol in the US) and salmeterol, which are used to treat respiratory conditions by inducing bronchodilation. Additionally, polymorphisms in the ADRB2 gene have been associated with varying responses to these medications, influencing both therapeutic outcomes and side effects.

Pharmacology

Beta-2 adrenergic receptors are also involved in the metabolic regulation, such as glycogenolysis and lipolysis. They are stimulated by both endogenous catecholamines and synthetic compounds, which can be used to enhance muscle relaxation and airway diameter in clinical settings.

Research

Ongoing research on the Beta-2 adrenergic receptor includes studies on its role in the cardiovascular system, its potential implications in metabolic disorders, and its genetic variations affecting individual responses to drugs.