Activity and localization of the Secretory Pathway Ca2+-ATPase isoform 1 (SPCA1) in different areas of the mouse brain during postnatal development

Ca2+ and Mn2+ play an important role in many events in the nervous system, ranging from neural morphogenesis to neurodegeneration. As part of the homeostatic control of these ions, the Secretory Pathway Ca2+-ATPase isoform 1 (SPCA1) mediates the accumulation of Ca2+ or Mn2+ with high affinity into Golgi reservoirs. This SPCA1 represents a relatively recently characterized P-type pump that is highly expressed in nervous tissue, but information on its involvement in neural maturation is currently lacking. In this study, we have analyzed the expression and distribution of the SPCA1 pump in mouse brain during postnatal development. RT-PCR and Western blot assays showed that SPCA1 is particularly highly expressed at nearly constant levels during this entire period of development in cortex, hippocampus, and cerebellum. In spite of the apparently unchanged expression levels, functional assays showed that SPCA-associated Ca2+-ATPase activity increased with the stage of development in these areas. Immunohistochemical studies pointed to SPCA1 localization in Golgi stacks of the soma and the initial part of primary dendritic trunk in main cortical, hippocampal and cerebellar neurons from the earliest postnatal stages. This suggests a potential role in intracellular signaling and in Golgi secretory processes involved in dendritic growth and in functional maturation of the mouse nervous system.