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
A Doença de Niemann-Pick é um distúrbio de armazenamento hereditário cujo problema principal reside na deficiência parcial ou total de esfingomielinase e/ou de suas isoenzimas, levando ao acúmulo de esfingomielina em todos os orgäos, principalmente no fígado, rins e cérebro. As alteraçöes da coagulaçäo na Doença de Niemann-Pick ainda säo pouco descritas, porém podem apresentar-se precose e isoladamente nos neonatos, precedendo os sinais e sintomas mais frequentes. Os autores apresentam neste relato um caso de paciente do sexo feminino, cinco meses de vida, com quadro de hemorragia grave aos 13 dias de vida após realizaçäo do Teste do Pezinho e aumento do volume abdominal progressivo desde o nascimento. O diagnóstico de Doença de Niemann-Pick foi dado após exclusäo das principais patologias com quadro semelhante e pelo achado de células histiocíticas com depósito citoplasmático espumoso no aspirado de medula óssea. Os autores destacam ainda suas características clínico-laboratoriais e diagnósticos diferenciais.