Cholinergic receptor nicotinic alpha 5 subunit (CHRNA5) (CHRNA5)

The Cholinergic receptor nicotinic alpha 5 subunit (CHRNA5) is a protein that serves as an accessory subunit within the pentameric nicotinic acetylcholine receptor (nAChR) complex (UniProt P30532). It is primarily found incorporated into heteromeric receptors such as the (alpha4beta2)2alpha5 subtype, where it significantly alters the receptor's biophysical properties, including increasing calcium permeability and the rate of desensitization (PubMed: 18203894). Unlike the alpha-4 or beta-2 subunits, the alpha-5 subunit does not contribute to the primary acetylcholine binding site but acts as a potent modulator of channel function (PubMed: 21460114). Genetic studies have identified the CHRNA5 gene as a major susceptibility locus for nicotine dependence and lung cancer, particularly through the rs16969968 polymorphism which results in a functional change in the receptor (PubMed: 18193049, PubMed: 18414406). This subunit is highly expressed in the medial habenula-interpeduncular nucleus pathway, where it mediates the aversive effects of high-dose nicotine, thereby regulating the upper limits of nicotine consumption (PubMed: 21278795). Pharmacologically, drugs like varenicline and nicotine interact with receptors containing this subunit to modulate dopamine release and smoking behavior (PubMed: 16810320). Due to its central role in addiction and its association with tobacco-related malignancies, CHRNA5 is considered a high-priority therapeutic target for smoking cessation and potentially for treating lung adenocarcinoma (PubMed: 21460114). Therapeutic challenges include the widespread distribution of nAChRs, which can lead to off-target effects in the cardiovascular and gastrointestinal systems (StatPearls: Nicotinic receptors).

Other names

Nicotinic acetylcholine receptor alpha 5nAChR alpha 5CHRNA5Cholinergic receptor nicotinic alpha 5Nicotinic acetylcholine receptor subunit alpha-5

The alpha 5 subunit acts as an accessory subunit that modulates the ion channel kinetics and calcium permeability of heteromeric nicotinic acetylcholine receptors (e.g., alpha-4-beta-2 or alpha-3-beta-4 complexes) without forming the primary ligand-binding site.