Functions as an integral cofactor in cell pH regulation by controlling plasma membrane-type Na(+)/H(+) exchange activity. Binds to and activates SLC9A1/NHE1 in a serum-independent manner, thus increasing pH and protecting cells from serum deprivation-induced death. Also plays a role in the regulation of cell proliferation and tumor growth by increasing the phosphatase activity of PPP3CA in a calcium-dependent manner. Activator of the calcineurin/NFAT signaling pathway. Involved in the cytoplasmic translocation of the transcription factor NFATC3 to the nucleus (By similarity). Interacts with PPP3CA. Interacts with SLC9A1/NHE1; the interaction occurs in a calcium-dependent manner. Interacts with SLC9A1/NHE1 (By similarity). Exported from the nucleus to the cytoplasm through a nuclear export signal (NES) pathway. May shuttle between nucleus and cytoplasm. Predominantly localized in a juxtanuclear region. Colocalizes with SLC9A3 in the juxtanuclear region and at the plasma membrane (By similarity). Belongs to the calcineurin regulatory subunit family. CHP subfamily.