Specific detection and deletion of the Sigma-1 receptor in neurons and glial cells for functional characterization in vivo

The chaperon protein sigma-1 receptor (S1R) has been discovered over forty years ago. Recent pharmacological studies using S1R exogenous ligands demonstrated a promising therapeutical potential of targeting the S1R for several neurological disorders. Although intensive in vitro studies have revealed S1Rs are mainly residing at the membrane of the endoplasmic reticulum (ER), the cell-specific in vivo expression pattern of S1Rs is still unclear, mainly due to the lack of a reliable detection method which also prevented a comprehensive functional analysis. Here, first, we identified a highly specific antibody using S1R knockout (KO) mice and established an immunohistochemical protocol involving a 1% SDS antigen retrieval step. Second, we characterized the S1R expression in the mouse brain and can demonstrate that the S1R is widely expressed: in principal neurons, interneurons, and all glial cell types. Finally, we generated a novel Cre-dependent S1R conditional KO mouse (S1R flox) to study cell type-specific functions of the S1R. As a proof of concept, we successfully ablated S1R expressions in neurons or microglia employing neuronal and microglial Cre-expressing mice, respectively. In summary, we provide powerful tools to cell-specifically detect, delete and functionally characterize S1R in vivo.