CHRNB

CHRNB refers to the family of genes encoding beta subunits of nicotinic acetylcholine receptors (nAChRs). In humans, the CHRNB family includes CHRNB1, CHRNB2, CHRNB3, and CHRNB4. These beta subunits are integral components of pentameric ligand-gated ion channels that mediate fast synaptic transmission in the nervous system and at the neuromuscular junction.

Structure and role: Each nAChR subunit has an extracellular N-terminus that binds acetylcholine, four transmembrane helices (M1–M4), and a cytoplasmic loop between M3 and M4. Beta subunits contribute to proper assembly, trafficking to the plasma membrane, and channel gating. They form heteromeric receptors with alpha subunits and influence ligand affinity, ion permeability, and desensitization kinetics, shaping receptor signaling properties.

Expression: CHRNB1 is primarily expressed in skeletal muscle and pairs with CHRNA1 to form the adult muscle-type receptor. CHRNB2, CHRNB3, and CHRNB4 are enriched in neuronal tissues and participate in brain and autonomic ganglia receptors, often combining with various alpha subunits to create diverse subtypes such as those containing β2 or β4.

Clinical significance: Mutations in CHRNB1 have been linked to congenital myasthenic syndromes, disorders characterized by fatigable weakness due to impaired neuromuscular transmission. Rare variants in CHRNB2 and CHRNB4 have also been reported in CMS or studied for their effects on receptor function. Genome-wide studies have linked variants near CHRNB2 and CHRNB3 with nicotine dependence and smoking behavior, reflecting the receptors’ role in reward pathways.

Research and overview: CHRNB genes are conserved across vertebrates and are studied in knockout models to understand neuromuscular signaling and neural circuits. They remain targets for pharmacological modulation in nicotine addiction and related neuromuscular disorders.

---