title: Analysis of membrane topology of neutral sphingomyelinase 2.
abstract: Neutral sphingomyelinase 2 (nSMase2), which has two hydrophobic segments at its NH(2)-terminus, plays an important role in ceramide-mediated cell regulation. Here, we investigated the membrane topology of nSMase2. When a double-tagged nSMase2 at both the NH(2) and COOH termini, was overexpressed in MCF-7 cells, the signals from both tags were detected in the inner leaflet of the plasma membrane. Furthermore, insertion of a tag into the internal sequence and green fluorescent protein-fused deletion mutants revealed that the entire catalytic region of the protein was located on the cytosolic face of the membranes and each hydrophobic segment is integrated into the membranes, but unlikely to span the entire membrane. These results indicate the presence of the enzyme in the inner leaflet of plasma membrane.
authors.affiliation: Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Tani
authors.forename: Yusuf A
authors.initials: YA
authors.lastname: Hannun
mesh_terms: D002462:Cell Membrane / Q000201:enzymology*; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D006801:Humans; D013108:Sphingomyelin Phosphodiesterase / Q000032:analysis* / Q000737:chemistry* / Q000235:genetics; D014407:Tumor Cells, Cultured
chemical_list: D049452:Green Fluorescent Proteins; C491484:SMPD3 protein, human; D013108:Sphingomyelin Phosphodiesterase