Cyclic nucleotide-gated (CNG) cation channels are heteromeric complexes made up of principal alpha and modulatory beta subunits. The alpha subunits consist of CNG1-3 and form functional cation channels by themselves. The beta subunits consist of CNG4-6 and, unlike the alpha subunits, do not form functional channels, but rather modify the properties of channels. formed by CNG1-3. CNG channels are essential components of olfactory and visual transduction. CNG proteins are present in cone and rod photoreceptors and in the pineal gland, and they contribute to modulating arterial blood pressure. CNG6, also designated cyclic-nucleotide-gated cation channel beta 3 (CNG-beta 3), is an integral membrane protein that can form a heterooligomeric complex with CNG-3. CNG-beta 3 is activated by cGMP and this activation leads to the depolarization of rod photoreceptors as a result of cation channel being opened. CNG-beta 3 is expressed in a small group of retinal photoreceptor cells and in testis. Mutations in the gene encoding for CNG-beta 3, can cause achromatopsia, an autosomal recessively inherited disease characterized by low visual acuity, photophobia, a lack of color discrimination, and nystagmus.
Function:
Visual signal transduction is mediated by a G-protein coupled cascade using cGMP as second messenger. This protein can be activated by cGMP which leads to an opening of the cation channel and thereby causing a depolarization of rod photoreceptors. Induced a flickering channel gating, weakened the outward rectification in the presence of extracellular calcium, increased sensitivity for L-cis diltiazem and enhanced the cAMP efficiency of the channel when coexpressed with CNGA3 (By similarity). Essential for the generation of light-evoked electrical responses in the red-, green- and blue sensitive cones.
Subunit:
Heterooligomeric complex with CNGA3.
Subcellular Location:
Membrane; Multi-pass membrane protein.
Tissue Specificity:
Expressed specifically in the retina.
DISEASE:
Defects in CNGB3 are the cause of Stargardt disease type 1 (STGD1) [MIM:248200]. STGD is one of the most frequent causes of macular degeneration in childhood. It is characterized by macular dystrophy with juvenile-onset, rapidly progressive course, alterations of the peripheral retina, and subretinal deposition of lipofuscin-like material. STGD1 inheritance is autosomal recessive.
Defects in CNGB3 are the cause of achromatopsia type 3 (ACHM3) [MIM:262300]; also known as Pingelapese blindness. ACHM3 is a congenital complete achromatopsia and is distinct from total colorblindness mainly because of the consistent concurrence of severe myopia.
Similarity:
Belongs to the cyclic nucleotide-gated cation channel (TC 1.A.1.5) family.
CNGB3 subfamily.
Contains 1 cyclic nucleotide-binding domain.
SWISS:
Q9NQW8
Gene ID:
54714
Database links:
Entrez Gene: 54714 Human
Omim: 605080 Human
SwissProt: Q9NQW8 Human
Unigene: 154433 Human
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