Calcium Pumps of Plasma Membrane and Cell Interior

Calcium entering the cell from the outside or from intracellular organelles eventually must be returned to the extracellular milieu or to intracellular storage organelles. The two major systems capable of pumping Ca2+ against its large concentration gradient out of the cell or into the sarco/endoplasmatic reticulum are the plasma membrane Ca2+ ATPases (PMCAs) and the sarco/endoplasmic reticulum Ca2+ ATPases (SERCAs), respectively. In mammals, multigene families code for these Ca2+ pumps and additional isoform subtypes are generated via alternative splicing. PMCA and SERCA isoforms show developmental-, tissue- and cell type-specific patterns of expression. Different PMCA and SERCA isoforms are characterized by different regulatory and kinetic properties that likely are optimized for the distinct functional tasks fulfilled by each pump in setting resting cytosolic or intra-organellar Ca2+ levels, and in shaping intracellular Ca2+ signals with spatial and temporal resolution. The loss or malfunction of specific Ca2+ pump isoforms is associated with defects such as deafness, ataxia or heart failure. Understanding the involvement of different Ca2+ pump isoforms in the pathogenesis of disease allows their identification as therapeutic targets for the development of selective strategies to prevent or combat the progression of these disorders.