Reactome | cGMP:CNG transports Na+ and Ca2+ into the rod outer segment

cGMP:CNG transports Na+ and Ca2+ into the rod outer segment

Stable Identifier

R-HSA-2514867

Type

Reaction [transition]

Species

Homo sapiens

Compartment

cytosol, extracellular region, plasma membrane

ReviewStatus

5/5

Locations in the PathwayBrowser

Expand all

General

SBML | | PDF

SVG | | PPTX | SBGN

cGMP:CNG transports Na+ and Ca2+ into the rod outer segment

Click the image above or here to open this reaction in the Pathway Browser
The layout of this reaction may differ from that in the pathway view due to the constraints in pathway layout

The cGMP-gated (CNG) channels are heterotetramers of three alpha subunits (CNGA1) and one beta subunit (CNGB1). Although the subunits bear structural similarities to voltage-gated potassium channels, the rod channel is only weakly voltage sensitive (Chen et al. 1993). Opening occurs with cGMP bound and rarely occurs in the absence of cGMP (hence the closed state is designated as CNG channel and the open status is designated as cGMP:CNG channel). In darkness, cGMP concentration is relatively high and cGMP-gated cation (CNG) channels are open to allow the influx of cations into the rod outer segment. The inward current is composed mainly of Na+ ions, with lesser contributions from Ca2+ ions and Mg2+ ions (Dhallan et al. 1992). The channel is outwardly rectifying so that over physiological membrane potentials, the inward current is proportional to the number of channels open and is nearly independent of voltage. Mutations in the CNG channel subunits can cause a recessive form of retinitis pigmentosa (https://sph.uth.edu/retnet/).

Literature References

PubMed ID	Title	Journal	Year
12432397	The heteromeric cyclic nucleotide-gated channel adopts a 3A:1B stoichiometry Zhong, H, Molday, LL, Molday, RS, Yau, KW	Nature	2002
16460277	CNG and HCN channels: two peas, one pod Craven, KB, Zagotta, WN	Annu. Rev. Physiol.	2006
12467591	Subunit stoichiometry of the CNG channel of rod photoreceptors. Weitz, D, Ficek, N, Kremmer, E, Bauer, PJ, Kaupp, UB	Neuron	2002
1379636	Human rod photoreceptor cGMP-gated channel: amino acid sequence, gene structure, and functional expression. Dhallan, RS, Macke, JP, Shows, TB, Reed, RR, Yau, KW, Nathans, J	J Neurosci	1992
12467592	Rod cyclic nucleotide-gated channels have a stoichiometry of three CNGA1 subunits and one CNGB1 subunit. Zheng, J, Trudeau, MC, Zagotta, WN	Neuron	2002
2578616	Induction by cyclic GMP of cationic conductance in plasma membrane of retinal rod outer segment Fesenko, EE, Kolesnikov, SS, Lyubarsky, AL	Nature	1985
2457685	Calcium and magnesium fluxes across the plasma membrane of the toad rod outer segment Nakatani, K, Yau, KW	J. Physiol. (Lond.)	1988
7682292	A new subunit of the cyclic nucleotide-gated cation channel in retinal rods Chen, TY, Peng, YW, Dhallan, RS, Ahamed, B, Reed, RR, Yau, KW	Nature	1993
2422346	Electrical properties of the light-sensitive conductance of rods of the salamander Ambystoma tigrinum Baylor, DA, Nunn, BJ	J. Physiol. (Lond.)	1986