Isoform-Specific Distribution of the Plasma Membrane Ca²⁺ ATPase in the Rat Brain

Regulation of cytoplasmic calcium is crucial both for proper neuronal function and cell survival. The concentration of Ca²⁺ in cytoplasm of a neuron at rest is 10,000 times lower than in the extracellular space, pointing to the importance of the transporters that extrude intracellular Ca²⁺. The family of plasma membrane calcium-dependent ATPases (PMCAs) represent a major component of the Ca²⁺ regulatory system. However, little information is available on the regional and cellular distribution of these calcium pumps. We used immunohistochemistry to investigate the distribution of each of the four PMCA isoforms (PMCA1-4) in the rat brain. Each isoform exhibited a remarkably precise and distinct pattern of distribution. In many cases, PMCA isoforms in a single brain structure were differentially expressed within different classes of neurons, and within different subcellular compartments. These data show that each isoform is independently organized and suggest that PMCAs may play a more complex role in calcium homeostasis than generally recognized.