Immunolocalization of the plasma membrane Ca2+ pump isoforms in the rat brain.

Ca2+ homeostasis in nerve cells is dependent on at least three mechanisms: Ca2+ channels, calcium-binding proteins and Ca2+ exchangers/pumps. Only limited information is available on the regional/cellular distribution of these Ca2+-regulating systems in the brain. The distribution of three of the isoforms of one of the systems, plasma membrane Ca2+-ATPase (PMCA), was analyzed in this study. Using antibodies against epitopes specific for each isoform, a map of the distribution of the pump in the whole brain was produced. The pump was mainly expressed in neurons and was apparently absent from glia cells. Isoform 1 was ubiquitous and occurred in varying, but always significant, concentrations in almost all nerve cells. Isoform 2 was abundant in cerebellar Purkinje cells but less concentrated in other brain regions. Isoform 3 had a predominantly extra neuronal location, e.g. it was abundant in the choroid plexuses. The three isoforms were found to be distributed in a highly characteristic manner, suggesting that nerve cells have different requirements for the preservation of their intracellular calcium homeostasis.