title: Acid sphingomyelinase and its redox amplification in formation of lipid raft redox signaling platforms in endothelial cells.
abstract: This study examined the role of acid sphingomyelinase (ASM) and its redox amplification in mediating the formation of lipid raft (LR) redox signaling platforms in coronary arterial endothelial cells (CAECs). Using small interference RNA (siRNA) of ASM, Fas ligand (FasL)-induced increase in ASM activity, production of ceramide, and LR clustering in CAECs were blocked, and clustered Fas was also substantially reduced in detergent-resistant membrane fractions of CAECs. LR clustering, gp91(phox) aggregation, and p47(phox) translocation to the LR clusters induced by FasL were also blocked in ASM-siRNA transfected CAECs. Corresponding to this reduction of LR clustering with NAD(P)H oxidase subunits in ASM-siRNA transfected CAECs, superoxide (O(2)(-*)) production was significantly decreased as measured by either ESR or fluorescent spectrometry. Interestingly, superoxide dismutase (SOD) not only scavenged (O(2)(-*)), but also markedly attenuated LR clustering. Xanthine/xanthine oxidase, an exogenous (O(2)(-*)) generating system, dramatically increased ASM activity and LR clustering in EC membrane and enhanced FasL-induced LR clustering, which were blocked by SOD. These results suggest that that ASM activates LR clustering to form redox signaling platforms, where (O(2)(-*)) production enhances ASM activity, and thereby results in a forwarding amplification of LR and redox signaling. This ASM-mediated feedforwarding mechanism may be critical for an efficient transmembrane signaling through LRs.
authors.affiliation: Department of Pharmacology and Toxicology, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298, USA.
authors.forename: Andrew Y
authors.initials: AY
authors.lastname: Zhang
authors.forename: Fan
authors.initials: F
authors.lastname: Yi
authors.forename: Si
authors.initials: S
authors.lastname: Jin
authors.forename: Min
authors.initials: M
authors.lastname: Xia
authors.forename: Qi-Zheng
authors.initials: QZ
authors.lastname: Chen
authors.forename: Erich
authors.initials: E
authors.lastname: Gulbins
authors.forename: Pin-Lan
authors.initials: PL
authors.lastname: Li
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D002518:Ceramides / Q000378:metabolism; D003331:Coronary Vessels / Q000166:cytology; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation; D053222:Fas Ligand Protein / Q000494:pharmacology; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D019255:NADPH Oxidases / Q000378:metabolism; D010084:Oxidation-Reduction; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism; D014162:Transfection; D019820:Xanthine / Q000494:pharmacology; D014969:Xanthine Oxidase / Q000494:pharmacology
chemical_list: D002518:Ceramides; D053222:Fas Ligand Protein; D034741:RNA, Small Interfering; D013481:Superoxides; D019820:Xanthine; D013482:Superoxide Dismutase; D014969:Xanthine Oxidase; D019255:NADPH Oxidases; D013108:Sphingomyelin Phosphodiesterase