Ca²⁺-ATPase

Ca²⁺-ATPases function to maintain a low cytoplasmic concentration of Ca²⁺ ions. They are high affinity, low capacitance transporters and complement the actions of the low affinity, high capacitance Na⁺/Ca²⁺ exchanger. Ca²⁺-ATPases are P-type ATPases and there are two variants: a plasma membrane-bound Ca²⁺-ATPase (PMCA) and a sacroplasmic reticulum Ca²⁺-ATPase (SERCA).

PMCA exists as a dimer within the plasma membrane of a wide variety of cell types and, using the energy released from ATP hydrolysis, transports Ca²⁺ ions out of the cell against the concentration gradient. SERCA is located in the sarcoplasmic reticulum (SR) of muscle cells and transports Ca²⁺ ions from the cytoplasm into the SR lumen during muscle relaxation. PMCA transports one Ca²⁺ ion per ATP molecule hydrolyzed, whilst SERCA can transport two. PMCAs are regulated by calmodulin and the phospholipid composition of the surrounding plasma membrane. Furthermore, PMCA can be phosphorylated by PKA, PKC, Src and FAK at specific residues to influence activity.

So far, only one human pathology has been linked to PMCA defects - deafness. However, SERCA defects have been implicated in a wide array of pathologies including heart failure, sperm motility defects, cataract formation, carcinogenesis, diabetes, and cardiac hypertension and hypertrophy.

External sources of pharmacological information for Ca²⁺-ATPase :

• BJP Guide

Ca²⁺-ATPase Gene Data