Sphingomyelin hydrolysis during apoptosis

Analysis of membrane topology of neutral sphingomyelinase 2

“…It has already been suggested that the hydrolysis of sphingomyelin occurs at the inner leaflet of the plasma membrane in response to activation of nSMases [4]. Furthermore, potential direct target molecules of ceramide, such as protein phosphatase2A, protein phosphatase1, and protein kinase Cf, are localized at the cytoplasmic region of cells [14,15].…”

“…After being rinsed with PBS and 50 mM NH 4 Cl in PBS, cells were permeabilized, if necessary, by 0.1% Triton X-100 in PBS for 5 min at room temperature or 5 lg/ml digitonin for 10 min on ice. After treatment with blocking buffer (2% FBS in PBS) for 15 min, the samples were incubated with anti-V5 (3 lg/ml; Invitrogen), anti-GFP (8 lg/ml; Invitrogen), anti-KDEL (1 lg/ml; Stressgen) or anti-giantin (1:300 dilution; Abcam) antibody with blocking buffer at room temperature for 2 h followed by anti-mouse or rabbit IgG-Alexa Fluor Ò 555 secondary antibody (Invitrogen) at room temperature for 1 h. All confocal images were taken with a laser-scanning confocal microscope (LSM 510 Meta; Carl Zeiss, Thornwood, NY).…”

“…Acid and alkaline SMases contribute to the hydrolysis of sphingomyelin in the lumenal border of cells, in the extracellular space, or in the endosomal system [3]. In contrast, it has been suggested that the magnesium-dependent neutral SMase (nSMase) functions in the inner leaflet of plasma membrane [4]. However, there is little information concerning the membrane topology and orientation of nSMase.…”

Reversion of Multidrug Resistance by SKI-II in SGC7901/DDP Cells and Exploration of Underlying Mechanisms

“…So a ceramide/S1P rheostat has been hypothesized to determine the fate of cell, such that the relative cellular concentrations of ceramide and S1P determine whether a cell proliferates or undergoes apoptosis (Andrieu-Abadie and Levade, 2002;Reynolds et al, 2004;Bieberich et al, 2008). At the same time, previous work using Dictyostelium discoideum as a model for studying drug resistance showed that mutants lacking sphingosine-1-phosphate (S1P) lyase, the enzyme that degrades S1P, had increased resistance to cisplatin, Zu-An Zhu 1 , Zheng-Qiu Zhu 2 , Hong-Xing Cai 3 , Ying Liu 4 * whereas mutants overexpressing the enzyme were more sensitive to the drug (Andrieu-Abadie and Levade, 2002). That means modulating the levels of sphingolipids in cells can be a powerful way to increase the sensitivity of tumor cells to cisplatin.…”

Both Sphingomyelin Synthases SMS1 and SMS2 Are Required for Sphingomyelin Homeostasis and Growth in Human HeLa Cells

“…To begin with, SM accumulates in the outer leaflet of the plasma membrane, and its high packing density and affinity for cholesterol likely contribute to the barrier function of this organelle. In addition, SM at the plasma membrane provides a reservoir of lipid signaling molecules that are liberated by acidic or neutral SMases in response to a variety of biological stimuli (8); these molecules include ceramide, sphingosine, and sphingosine 1-phosphate, and have been implicated in the regulation of cell proliferation, differentiation, and apoptosis (9,10). As SM has a strong capacity to form microdomains, its production in the trans Golgi may affect the lateral organization of other membrane components and hence provide a physical basis for sorting events that help establish the compositional and functional differences between the endoplasmic reticulum, plasma membrane, and Golgi itself (11).…”