Acetylcholine receptor subunit alpha (CHRNA)

The acetylcholine receptor α subunit is an integral membrane protein making up the principal agonist binding site of nicotinic acetylcholine receptors (nAChRs). Each nAChR is composed of five subunits, typically two α and three others, assembled into a ligand-gated ion channel. Binding of acetylcholine to sites formed by the α subunit and adjacent subunit triggers conformational changes that open the channel for cation influx, mediating rapid synaptic transmission. Multiple α subunit isoforms exist—CHRNA1 is fundamental to muscle nAChRs, while CHRNA2–CHRNA10 are important in neuronal nAChRs, conferring distinct pharmacological and physiological properties. The α subunit is a key therapeutic target in diseases affecting neuromuscular junctions and neural signaling, and is also the major antigen in autoimmune myasthenia gravis.

Other names

Nicotinic acetylcholine receptor alpha subunitnAChR α subunitCHRNA1CHRNA2etc. (denoting specific genes)Main immunogenic region (MIR, referring to an epitope within the subunit)

Channel agonists activate cation influx by binding at the α subunit interface, depolarizing the membrane. Channel antagonists block acetylcholine binding or channel opening, inhibiting signaling. Toxins (e.g., α-bungarotoxin) irreversibly bind the α subunit, blocking neurotransmission. Allosteric modulators alter receptor sensitivity and desensitization.