A study of the organellar Ca2(+)-transport ATPase isozymes in pig cerebellar Purkinje neurons.

Pig cerebellar Purkinje neurons express a high level of Ca2(+)-transport ATPases in their intracellular Ca2+ stores. This was shown at the mRNA level by Northern blotting and in situ hybridization and at the protein level by Western blotting and immunocytochemistry. The majority of the Ca2(+)-transport ATPases in these neurons belongs to the SERCA2b type (i.e., the Ca2(+)-pump isoform found in most nonmuscle cells). The SERCA2a (cardiac/slow-twitch skeletal/smooth muscle) Ca2(+)-pump isoform is expressed only at very low levels. The main Ca2(+)-pump messenger is 6.0 kilobases long and belongs to a class 4-type processing of SERCA2, which is exclusively confined to the cerebrum and cerebellum. Phospholamban, a regulator of the SERCA2 Ca2(+)-transport ATPase in cardiac/slow-twitch skeletal/smooth muscle, could not be detected in Purkinje neurons.