Plasma membrane Ca2+ ATPase

[3] The PMCA and the sodium calcium exchanger (NCX) are together the main regulators of intracellular Ca2+ concentrations.

[4] PMCAs belong to the family of P-type primary ion transport ATPases which form aspartyl phosphate intermediates.

It binds tightly to Ca2+ ions (has a high affinity, with a Km of 100 to 200 nM) but does not remove Ca2+ at a very fast rate.

[3] Calcium is an important second messenger, so its levels must be kept low in cells to prevent noise and keep signalling accurate.

[7] The NCX is better suited for removing large amounts of Ca2+ quickly, as is needed in neurons after an action potential.

Additionally, it has been shown that PMCA activity is modulated and partly powered by glycolysis in neuronal somata and dendrites.

[9] It is thought that the PMCA pump has 10 segments that cross the plasma membrane, with both C and N termini on the inside of the cell.

[5] PMCA types 1, 2, and 4 have been found in glial cells called astrocytes in mammals, though it was previously thought that only the NCX was present in glia.

Improperly functioning PMCA proteins have been found associated with conditions such as sensorineural deafness, diabetes, and hypertension.

PMCA2 expression falls on weaning, leading to calcium-induced apoptosis and mammary gland involution.

Persistent PMCA2 expression in certain breast cancers lowers calcium levels inside malignant cells, allowing them to avoid apoptosis.