SOLUTE CARRIER FAMILY 24 (SODIUM/POTASSIUM/CALCIUM EXCHANGER), MEMBER 2; SLC24A2

Alternative titles; symbols

• SODIUM/POTASSIUM/CALCIUM EXCHANGER 2; NCKX2
• RETINAL CONE SODIUM/POTASSIUM/CALCIUM EXCHANGER

HGNC Approved Gene Symbol: SLC24A2

Cytogenetic location: 9p22.1-p21.3 Genomic coordinates (GRCh38): 9:19,507,451-20,307,887 (from NCBI)

▼ Description
The outer segment of retinal rod and cone photoreceptors contains electrogenic sodium-calcium exchangers which mediate a light-induced decrease in free calcium concentration. This function in cones is performed by SLC24A2 (Prinsen et al., 2000).

▼ Cloning and Expression
Using primers designed from chicken Nckx2 to amplify NCKX2 from a human retina cDNA library, followed by 5-prime and 3-prime RACE, Prinsen et al. (2000) cloned a full-length NCKX2 cDNA. The deduced 661-amino acid protein contains 12 transmembrane segments. NCKX2 shares 76.5% and 89.6% amino acid identity with chicken and rat Nckx2, respectively. Prinsen et al. (2000) also identified an alternatively spliced variant that results in a protein lacking a 17-amino acid segment between the sixth and seventh transmembrane domains. Northern blot analysis detected an approximately 10.5-kb NCKX2 transcript in human retina and frontal, temporal, parietal, and occipital lobes and cerebellum, but not in lung. In situ hybridization of chicken retina detected Nckx2 within cones, in some cells of the retinal ganglion cell layer, and in cell bodies at the base of the outer nuclear layer.

▼ Gene Function
Prinsen et al. (2000) demonstrated potassium-dependent sodium-calcium exchange activity after heterologous expression of human and chicken cone NCKX2 cDNAs in cultured insect cells. The shorter splice variants of NCKX2 showed the higher activity.

▼ Mapping
By genomic sequence analysis, Kraev et al. (2001) mapped the SLC24A2 gene to chromosome 9p22.1-p22.3.