CHRNA9

CHRNA9 is a gene that encodes the alpha-9 subunit of the nicotinic acetylcholine receptor (nAChR). The nAChR is a type of ionotropic receptor that is activated by the neurotransmitter acetylcholine. The CHRNA9 gene is located on the long arm of chromosome 4 (4q24) in humans.

Structure

The CHRNA9 gene spans approximately 6.5 kilobases and consists of 6 exons. The encoded protein is a member of the ligand-gated ion channel family and is composed of 479 amino acids. The protein has a large extracellular N-terminal domain, four transmembrane domains (M1-M4), and a large intracellular loop between the M3 and M4 domains.

Function

The alpha-9 subunit can form a functional homomeric receptor, but it also forms heteromeric receptors with the alpha-10 subunit. These receptors are expressed in various tissues, including the cochlea, skin, and immune system cells. In the cochlea, they play a crucial role in the efferent inhibition of outer hair cells, which is important for the protection of the ear from loud noise. In the skin, they are involved in keratinocyte adhesion and migration, processes that are important for wound healing. In the immune system, they modulate inflammation and immune responses.

Clinical significance

Mutations in the CHRNA9 gene have been associated with non-syndromic hearing loss. In addition, the expression of the alpha-9 subunit has been found to be altered in various types of cancer, including breast cancer and lung cancer, suggesting a potential role in tumorigenesis.

See also

• Nicotinic acetylcholine receptor
• Ionotropic receptor
• Acetylcholine
• Chromosome 4