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. Interacts with PPP3CA. Interacts with SLC9A1/NHE1; the interaction occurs in a calcium-dependent manner. Predominantly localized in a juxtanuclear region. Colocalizes with SLC9A3 in the juxtanuclear region and at the plasma membrane (By similarity). Exported from the nucleus to the cytoplasm through a nuclear export signal (NES) pathway. May shuttle between nucleus and cytoplasm. Expressed in malignantly transformed cells but not detected in normal tissues. Belongs to the calcineurin regulatory subunit family. CHP subfamily.