Ca²⁺ has proven to be a universal signaling molecule in excitable and non-excitable cells. However, being that its intracellular concentration is 1000 time lower than the extracellular milieu, it is important for the cell to keep this ratio for proper function. NCX, a Na⁺/Ca²⁺ exchanger is responsible for most of the efflux of Ca²⁺ out from the cell. The NCX transporter is a member of the SLC8 family of solute carriers which in turn belong to the CaCA superfamily.