Sterol carrier protein 2 (non-specific lipid transfer protein) is localized in membranous fractions of Leydig cells and Sertoli cells but not in germ cells

Abstract The cellular and subcellular distribution of sterol carrier protein 2 (SCP 2 ; nsL-TP) was reinvestigated in rat testicular cells by Western blotting and immunocytochemistry, using the affinity purified antibody against rat liver SCP 2 . Western blot analysis revealed high levels of the protein in the somatic cells of the testis, e.g., Leydig and Sertoli cells whereas it could not be detected in germ cells. This cellular localization of SCP 2 was confirmed by Northern blotting. Immunocytochemical techniques revealed that in Leydig cells, immunoreactive proteins were concentrated in peroxisomes. Although SCP 2 was also detected in Sertoli cells, a specific subcellular localization could not be shown. SCP 2 was absent from germ cells. Analysis of subcellular fractions of Leydig cells showed that SCP 2 is membrane bound without detectable amounts in the cytosolic fraction. These results are at variance with data published previously which suggested that in Leydig cells a substantial amount of SCP 2 was present in the cytosol and that the distribution between membranes and cytosol was regulated by luteinizing hormone. The present data raise the question in what way SCP 2 is involved in cholesterol transport between membranes in steroidogenic cells but also in non-steroidogenic cells.