Subject(s)
Animals , Carrier Proteins/physiology , Cholesterol, LDL/metabolism , Endoplasmic Reticulum/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , Membrane Glycoproteins/physiology , Membrane Proteins/metabolism , Niemann-Pick Diseases/etiology , Cell Line , Microscopy, Fluorescence , Niemann-Pick Diseases/metabolism , PhenotypeABSTRACT
The proposed role of Niemann-Pick type C1 protein (NPC1) in the delivery of low-density lipoprotein (LDL) cholesterol to the sterol regulatory element binding protein (SREBP):SREBP cleavage activation protein (SCAP) complex in the endoplasmic reticulum has been largely based on indirect studies and remains contentious. The major aim of the present study was to assess whether NPC1 is involved in the delivery of LDL cholesterol to the SREBP:SCAP complex. A cell line stably expressing green fluorescence protein-SCAP was cultured in the presence of U18666A, which can induce a Niemann-Pick type C disease phenotype, in order to locate the SREBP:SCAP complex by fluorescence microscopy. Our major finding was that defective NPC1 caused a delay in the ability of LDL cholesterol to suppress SREBP processing. This was shown in a time-course experiment by the effect of LDL on green fluorescence protein-SCAP movement when cells were treated with pharmacological agents to induce a Niemann-Pick type C disease phenotype. We demonstrated directly by fluorescence microscopy that defective NPC1 causes a delay in LDL cholesterol delivery to the endoplasmic reticulum where SCAP senses cholesterol.
Subject(s)
Animals , Carrier Proteins/physiology , Cholesterol, LDL/metabolism , Endoplasmic Reticulum/metabolism , Intracellular Signaling Peptides and Proteins/metabolism , Membrane Glycoproteins/physiology , Membrane Proteins/metabolism , Niemann-Pick Diseases/etiology , Cell Line , Microscopy, Fluorescence , Niemann-Pick Diseases/metabolism , PhenotypeABSTRACT
Niemann-Pick type C (NPC) fibroblasts present a large concentration of cholesterol in their cytoplasm due to a still unidentified deficiency in cholesterol metabolism. The influence of dimethylsulfoxide (DMSO) on the amount of intracellular cholesterol was measured in 8 cultures of normal fibroblasts and in 7 fibroblast cultures from NPC patients. DMSO was added to the fibroblast cultures at three different concentrations (1, 2 and 4 percent, v/v) and the cultures were incubated for 24 h. Sphingomyelinase activity was significantly increased in both groups of cells only when incubated with 2 percent DMSO (59.4 9.1 and 77.0 9.1 nmol h-1 mg protein-1, controls without and with 2 percent DMSO, respectively; 47.7 5.2 and 55.8 4.1 nmol h-1 mg protein-1, NPC without and with 2 percent DMSO, respectively). However, none of the DMSO concentrations used altered the amount of cholesterol in the cytoplasm of NPC cells (0.704 0.049, 0.659 0.041, 0.688 0.063 and 0.733 0.088 mg/mg protein, without DMSO, 1 percent DMSO, 2 percent DMSO and 4 percent DMSO, respectively). This finding suggests that sphingomyelinase deficiency is a secondary defect in NPC and shows that DMSO failed to remove the stored cholesterol. These data do not support the use of DMSO in the treatment of NPC patients
Subject(s)
Humans , Cholesterol/metabolism , Dimethyl Sulfoxide/pharmacology , Fibroblasts/drug effects , Niemann-Pick Diseases/metabolism , Solvents/pharmacology , Sphingomyelin Phosphodiesterase/drug effects , Analysis of Variance , Cells, Cultured/drug effects , Cholesterol/analysis , Dimethyl Sulfoxide/therapeutic use , Niemann-Pick Diseases/drug therapy , Solvents/therapeutic useABSTRACT
Se hace una revisión de la enfermedad de Niemann-Pick que es una alteración innata del metabolismo de los fosfolípidos, la ESPINGOMIELINA, que se acumula en los lisosomas, constituyendo la enfermedad lisosomal, debido a una alteración cualitativa o cuantitativa de la ESZPINGOMIELINASA. La enfermedad es transmitida en forma autosómica recesiva, alterando los diversos órganos, especialmente el sistema nervioso y el fondo de ojo en el cual se observa en la mácula una mancha de color cereza. A continuación se presenta el caso problema en un indígena puro del Cañar-Ecuador (años anteriores se encontró otro caso que fue descrito por su extrema rareza), existe consanguinidad; hepatoesplenomegalia, mancha roja en mácula y células espúmosas en médula ósea. Un hermano falleció con identicas características clínicas.