cyclicnucleotidegated

Cyclic nucleotide-gated channels are a class of ion channels that are permeable to cations such as sodium (Na+), potassium (K+), and calcium (Ca2+). Their unique characteristic is that their opening and closing are regulated by the binding of cyclic nucleotides, specifically cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). These channels are crucial for signal transduction in various sensory pathways.

There are several types of cyclic nucleotide-gated (CNG) channels, often categorized by their subunit composition. These subunits can be homomeric, formed from identical subunits, or heteromeric, composed of different subunits. The specific combination of subunits influences the channel's properties, including its sensitivity to cyclic nucleotides and its ion selectivity.

CNG channels play vital roles in photoreception and olfaction. In the retina, CNG channels in photoreceptor cells are open in the dark, allowing a steady influx of cations. When light strikes the photoreceptor, cGMP levels decrease, causing the channels to close, leading to a hyperpolarization of the cell and the generation of a visual signal. In the olfactory epithelium, CNG channels are activated by odorants, leading to depolarization of olfactory neurons and the perception of smell. Beyond sensory systems, CNG channels have also been identified in other tissues and are implicated in various cellular processes, including neurotransmission and smooth muscle function.