Specific detection and deletion of the sigma‐1 receptor widely expressed in neurons and glial cells in vivo. Issue 6 (29th September 2022) - Liu, Qing
Abstract: The chaperon protein sigma‐1 receptor (S1R) has been discovered over 40 years ago. Recent pharmacological studies using S1R exogenous ligands demonstrated a promising therapeutical potential of targeting the S1R in 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 because of 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% sodium dodecyl sulphate (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. In addition, unlike reported in previous studies, we showed that the S1R expression in astrocytes is not colocalized with the astrocytic cytoskeleton protein GFAP. Thus, our results raise concerns over previously reported S1R properties. Finally, we generated a 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. Abstract : The cellular expression and functions of the sigma‐1 receptor (S1R) in the central nervous system (CNS) still remain elusive because of a lack of appropriate tools. Here, we took advantage of S1R knockout mice to identify a commercial antibody (Ab #61994 ) specifically recognizing S1Rs in immunoblots. We further established a simple immunohistochemical antigen retrieval method employing 1% SDS to reliably detect S1Rs with Ab #61994 in brain vibratome sections, demonstrating a wide expression of S1Rs in neurons and all glial cell types. We also generated a new S1R flox mouse for Cre‐dependent conditional deletion of S1Rs for functional analysis in vivo.