cGMPgateda

cGMPgateda is a term used to describe the alpha subunit of cyclic guanosine monophosphate–gated ion channels, a component of the cyclic nucleotide-gated (CNG) channel family. In most animals, cGMPgateda corresponds to CNGA subunits (CNGA1, CNGA2, CNGA3) that assemble with CNGB subunits to form functional channels. The alpha subunits provide the primary binding site for cyclic nucleotides and contribute to pore gating, while beta subunits modulate ligand affinity, channel kinetics, and sensitivity to cAMP.

CNG channels open in response to binding of cGMP (and in some isoforms cAMP) and are permeable to cations, including Na+ and Ca2+. The resulting current influences the electrical state of the cell. In photoreceptors, high intracellular cGMP in darkness keeps channels open, contributing to the dark current; light activation activates phosphodiesterase, lowers cGMP, and closes the channels, leading to hyperpolarization and reduced transmitter release. In olfactory neurons, cGMP–gated channels participate in odorant signaling and adaptation.

These channels are broadly expressed in the retina and olfactory epithelium, with subunit composition varying by tissue. Mutations in CNGA genes can underlie inherited visual disorders such as achromatopsia and other retinal dysfunctions, while olfactory signaling can also be affected by subunit defects. Research on cGMPgateda subunits informs understanding of sensory transduction and potential gene- or pharmacological therapies.

Note: The term cGMPgateda is not widely used in canonical nomenclature; it is presented here to describe the alpha subunit component of CNG channels.