Immunolocalization of STIM1 in the mouse brain.

Capacitative Calcium Entry (CCE) in neurons seems to depend, as in non-excitatory cells, on endoplasmic reticulum calcium sensors STIM1 or STIM2. We show localization of STIM1 in the mouse brain by immunohistochemistry with a specific antibody. STIM1 immunoreactivity has wide, but not uniform, distribution throughout the brain and is observed in neuropil and cells. The most intensive immunoreactivity is observed in Purkinje neurons of cerebellum. High/moderate levels of immunostaining are found in hippocampus, cerebral cortex and in cortico-medial amygdala, low in thalamus and basolateral amygdala. Co-staining with anti-NeuN antibody identify STIM1 immunopositive cells as neurons. Real time PCR demonstrates that Stim2 expression is 7-fold higher than that of Stim1 in hippocampus and 3-fold in other regions. Immunoblotting confirms that levels of STIMs vary in different brain regions. The data show that STIM1 and STIM2 are present in the brain, thus both can be involved in CCE, depending on neuronal type.