CNGA4 encodes a pore-forming subunit of the olfactory cyclic nucleotide-gated (CNG) channel, a heteromeric complex also containing CNGA2 and CNGB1b in a 2:1:1 stoichiometry 1. In olfactory sensory neuron cilia, CNGA4 mediates cAMP-dependent Ca²⁺ and cation influx, converting chemical odorant stimulation into electrical signals 2. The channel conducts both cAMP- and cGMP-gated currents with permeability for monovalent and divalent cations. CNGA4 contains an IQ-type calmodulin-binding site critical for rapid odorant adaptation; Ca²⁺-bound calmodulin binds this site to inhibit channel activity, providing negative feedback that enables sensory neurons to quickly desensitize and readapt to sustained odorant exposure 34. CNGA4 also contributes a functional module that stabilizes the channel's open state at physiological cAMP concentrations 5. Additionally, the CNGA2 N-terminus, required for PIP3-mediated channel regulation, is functionally silent in heteromeric channels, suggesting CNGA4's structural context modulates regulatory mechanisms 6. Disease relevance is limited; CNGA4 hypermethylation has been observed in carcinogen-exposed cells and lung cancer tissues, though its direct pathogenic role remains unclear 7.