Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To analyze the contribution of vesicular trafficking pathways in cellular cholesterol transport we examined the effects of selected endosomal Rab proteins on cholesterol distribution by filipin staining. Transient overexpression of Rab11 resulted in prominent accumulation of free cholesterol in Rab11-positive organelles that sequestered transferrin receptors and internalized transferrin. Sphingolipids were selectively redistributed as pyrene-sphingomyelin and sulfatide cosequestered with Rab11-positive endosomes, whereas globotriaosyl ceramide and GM2 ganglioside did not. Rab11 overexpression did not perturb the transport of 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine-perchlorate-labeled low-density lipoprotein (LDL) to late endosomes or the Niemann-Pick type C1 (NPC1)-induced late endosomal cholesterol clearance in NPC patient cells. However, Rab11 overexpression inhibited cellular cholesterol esterification in an LDL-independent manner. This effect could be overcome by introducing cholesterol to the plasma membrane by using cyclodextrin as a carrier. These results suggest that in Rab11-overexpressing cells, deposition of cholesterol in recycling endosomes results in its impaired esterification, presumably due to defective recycling of cholesterol to the plasma membrane. The findings point to the importance of the recycling endosomes in regulating cholesterol and sphingolipid trafficking and cellular cholesterol homeostasis.
Mol Biol Cell 2002 Sep
PMID:Modulation of cellular cholesterol transport and homeostasis by Rab11. 1222 Nov 19

Types A and B Niemann-Pick disease (NPD) are lipid storage disorders caused by the deficient activity of acid sphingomyelinase (ASM). In humans, NPD is associated with the dysfunction of numerous organs including the lung. Gene targeting of the ASM gene in transgenic mice produced an animal model with features typical of NPD, including pulmonary inflammation. To assess mechanisms by which ASM perturbed lung function, we studied lung morphology, surfactant content, and metabolism in ASM-deficient mice in vivo. Pulmonary inflammation, with increased cellular infiltrates and the accumulation of alveolar material, was associated with alterations in surfactant content. Saturated phosphatidylcholine (SatPC) content was increased twofold, and sphingomyelin content was increased 5.5-fold in lungs of the ASM knockout (ASMKO) mice. Additional sphingomyelin enhanced the sensitivity of surfactant inhibition by plasma proteins. Clearance of SatPC from the lungs of ASMKO mice was decreased. Catabolism of SatPC by alveolar macrophages from the ASMKO mouse was significantly decreased, likely accounting for decreased pulmonary SatPC in vivo. In summary, ASM is required for normal surfactant catabolism by alveolar macrophages in vivo. Alterations in surfactant composition, including increased sphingomyelin content, contributed to the abnormal surfactant function observed in the ASM-deficient mouse.
Am J Physiol Lung Cell Mol Physiol 2003 Mar
PMID:Alveolar lipoproteinosis in an acid sphingomyelinase-deficient mouse model of Niemann-Pick disease. 1249 43

In this study, we analyzed the intracellular mechanisms leading to basic fibroblast growth factor (bFGF)-dependent production of NO in Chinese hamster ovary (CHO)-K1 cells and a possible physiological role for such an effect. bFGF induces NO production through the activation of the endothelial form of NO synthase (eNOS), causing a subsequent increase in the cGMP levels. In these cells, the activation of eNOS by bFGF is Ca(2+)- and mitogen-activated protein kinase-independent. The translocation of the enzyme from the plasma membrane, where it is located in caveolae bound to caveolin 1, to the cytosol is the crucial step for the synthesis of NO through the eNOS isoform. We demonstrate that bFGF activates a sphingomyelinase to synthesize ceramide, which, in turn, allows the dissociation of eNOS from caveolin 1 and its translocation to the cytosol in the active form, where it catalyzes the synthesis of NO. In fact, drugs interfering with sphingomyelinase activity blocked bFGF activation of eNOS, and an increase in ceramide content was detected after bFGF treatment. Moreover, in fibroblasts derived from patients with Niemann-Pick disease, in which the enzyme is genetically inactive, bFGF is unable to elicit eNOS activation. The NO produced after bFGF treatment, through the activation of guanylyl cyclase and protein kinase G, mediates a mitogen-activated protein kinase-independent cell proliferation. In conclusion, our data show that, in CHO-K1 cells, bFGF regulates the activity of eNOS through a novel intracellular pathway, involving the induction of ceramide synthesis and that the NO released participates in bFGF proliferative activity.
Mol Pharmacol 2003 Feb
PMID:Basic fibroblast growth factor activates endothelial nitric-oxide synthase in CHO-K1 cells via the activation of ceramide synthesis. 1252 1

Niemann-Pick type C (NPC) disease is a fatal recessively inherited lysosomal cholesterol-sphingolipidosis. Mutations in the NPC1 gene cause approximately 95% of the cases, the rest being caused by NPC2 mutations. Here the molecular basis of a severe infantile form of the disease was dissected. The level of NPC1 protein in the patient fibroblasts was similar to that in control cells. However, the protein was partially mislocalized from late endocytic organelles diffusely to the cell periphery. In contrast, NPC2 was upregulated and accumulated in cholesterol storing late endocytic organelles. Two point mutations and a four-nucleotide deletion were identified in the NPC1 gene, leading to the amino acid substitutions C113R, P237S and deletion of 37 C-terminal amino acids (delC). Overexpression of individual NPC1 mutations revealed that delC produced an unstable protein, wild-type and NPC1-P237S colocalized with Rab7-positive late endosomes whereas NPC1-C113R localized to the ER, Rab7-negative endosomes and the cell surface. Expression of wild-type or NPC1-P237S cleared the lysosomal cholesterol accumulation in NPC1-deficient cells whereas C113R or delC did not. In the Finnish and Swedish population samples, alleles carrying C113R or delC were not identified, whereas approximately 5% of the alleles carried P237S. Our studies identify P237S as a prevalent NPC1 polymorphism and delC and C113R as deleterious NPC1 mutations. Moreover, they show that delC leads to rapid degradation of NPC1 and C113R to endocytic missorting of the protein. These changes are accompanied by lysosomal accumulation of NPC2, suggesting that NPC1 governs the endocytic transport of NPC2.
Hum Mol Genet 2003 Feb 01
PMID:Defective endocytic trafficking of NPC1 and NPC2 underlying infantile Niemann-Pick type C disease. 1255 80

Niemann-Pick C (NPC) disease is an autosomal recessive neurovisceral lysosomal storage disorder that results in defective intracellular transport of cholesterol. The major form of human NPC (NPC1) has been mapped to chromosome 18, the NPC1 gene (NPC1) has been sequenced and several mutations have been identified in NPC1 patients. A feline model of NPC has been characterized and is phenotypically, morphologically, and biochemically similar to human NPC1. Complementation studies using cultured fibroblasts from NPC affected cats and NPC1 affected humans support that the gene responsible for the NPC phenotype in this colony of cats is orthologous to human NPC1. Using human-based PCR primers, initial fragments of the feline NPC cDNA were amplified and sequenced. From these sequences, feline-specific PCR primers were generated and designed to amplify six overlapping bands that span the entire feline NPC1 open reading frame. A single base substitution (2864G-C) was identified in NPC1 affected cats. Obligate carriers are heterozygous at the same allele and a PCR-based assay was developed to identify the geneotype of all cats in the colony. The mutation results in an amino acid change from cysteine to serine (C955S). Several of the mutations identified in people occur in the same region. Marked similarity exists between the human and feline NPC1 cDNA sequences, and is greater than that between the human and murine NPC1 sequences. The human cDNA sequence predicts a 1278aa protein with a lysosomal targeting sequence, several trans-membrane domains and extensive homology with other known mediators of cholesterol homeostasis.
Mol Genet Metab 2003 Jun
PMID:Mutation analysis of feline Niemann-Pick C1 disease. 1280 39

Normal murine bone marrow cells were transduced with a retroviral vector to overexpress and release human acid sphingomyelinase (ASM). The transduced cells were then transplanted intravenously into 3-day-old, irradiated ASM-deficient mice, a model of human Niemann-Pick disease (NPD). At 4 weeks, engrafted mice received intracerebral injections of mesenchymal stem cells obtained from the original, transduced bone marrow. By 16 weeks, most of the treated NPD mice had near-normal levels of ASM activity in their tissues, including the brain; dramatically improved histology; and marked reductions in sphingomyelin. Cerebellar function also was normal, and the number of Purkinje cells was > 80% of normal. Remarkably, in certain regions of the cerebellum many of the surviving Purkinje cells expressed human ASM RNA, suggesting that either they were donor-derived or that the transplanted bone marrow cells had fused with existing Purkinje cells. However, despite these positive results, by 24 weeks the ASM activities were dramatically reduced and cerebellar function began to decline, coincident with the detection of anti-human ASM antibodies in the plasma. We conclude that this gene therapy procedure might be useful in Type A NPD and other neurological lysosomal storage disorders, particularly since it is an approach that could be beneficial for both the neurological and the visceral organ features of these diseases.
Mol Ther 2003 Dec
PMID:Ex vivo gene therapy using bone marrow-derived cells: combined effects of intracerebral and intravenous transplantation in a mouse model of Niemann-Pick disease. 1466 89

Recent data demonstrate that inhibition of 3-hydroxy-3-methylglutaryl-CoA reductase restores normal signal transducer and activator of transcription-1 and inducible nitric oxide synthase expression regulation in cystic fibrosis (CF) cells through the modulation of RhoA function. These findings lead to the hypothesis that alterations in the cholesterol synthesis pathway may be an initiating factor in CF-related cell signaling regulation. A disease with a known lesion in the cholesterol synthesis pathway is Niemann-Pick type C (NPC). The hypothesis of this study is that CF cells and NPC fibroblasts share a common mechanistic lesion and should exhibit similar cell signaling alterations. NPC fibroblasts exhibit similar alterations in signal transducer and activator of transcription-1, RhoA, SMAD3, and nitric oxide synthase protein expression that characterize CF. Further comparison reveals NPC-like accumulation of free cholesterol in two cultured models of CF epithelial cells. These data identify novel signaling changes in NPC, demonstrate the cholesterol-synthesis pathway is a likely source of CF-related cell signaling changes, and that cultured CF cells exhibit impaired cholesterol processing.
Am J Respir Cell Mol Biol 2004 Nov
PMID:Mechanistic similarities between cultured cell models of cystic fibrosis and niemann-pick type C. 1525 87

In normal human skin fibroblasts (HSFs), fluorescent glycosphingolipid analogues are endocytosed and sorted into two pools, one that is recycled to the plasma membrane and one that is transported to the Golgi complex. Here, we investigated glycosphingolipid recycling in Niemann-Pick type A and C lipid storage disease fibroblasts (NPFs). Cells were incubated with a fluorescent analogue of lactosylceramide (LacCer) at 16 degrees C to label early endosomes (EEs), shifted to 37 degrees C, and lipid recycling was quantified. Using dominant negative rabs, we showed that, in normal HSFs, LacCer recycling was rapid (t1/2 approximately 8 min) and mainly rab4-dependent. In NPFs, LacCer recycling was delayed (t1/2 approximately 30-40 min), and rab4-dependent recycling was absent, whereas rab11-dependent recycling predominated. Transferrin recycling via the rab4 pathway was similarly perturbed in NPFs. Compared with normal HSFs, EEs in NPFs showed high cholesterol levels and an altered organization of rab4. In vitro extraction of rab4 (but not rab11) with GDP dissociation inhibitor was severely attenuated in NPF endosomal fractions. This impairment was reversed with cholesterol depletion of isolated endosomes or with high-salt treatment of endosomes. These data suggest that abnormal membrane recycling in NPFs results from specific inhibition of rab4 function by excess cholesterol in EEs.
Mol Biol Cell 2004 Oct
PMID:Elevated endosomal cholesterol levels in Niemann-Pick cells inhibit rab4 and perturb membrane recycling. 1529 53

Chitotriosidase is a human chitinase produced by macrophages. Its enzymatic activity is markedly elevated in serum of patients suffering from lysosomal storage disorders, as well as other diseases in which macrophages are activated. Therefore, it is a useful tool as a secondary marker in the diagnosis of several disorders including Gaucher disease type 1 and Niemann-Pick disease. The determination of chitotriosidase levels as a diagnosis complement in some lysosomal storage disorders and in enzyme replacement therapy follow-up of Gaucher disease patients is of great importance. However, the fact that a mutation caused by a 24-bp duplication in the CHIT1 gene resulting in deficiency of plasma chitotriosidase activity is very frequent makes the establishment of the frequency of this mutation in different population groups necessary. Furthermore, in order to validate the use of chitotriosidase activity as a marker, it is indispensable to screen individuals for this particular mutation. In this work, we present the results of a study where the allelic frequency of the above mentioned CHIT1 gene mutation was determined in the Portuguese population by real-time PCR. The frequency of carriers encountered in this sample of Portuguese individuals was of 37%.
Blood Cells Mol Dis
PMID:Allelic frequency determination of the 24-bp chitotriosidase duplication in the Portuguese population by real-time PCR. 1552 58

Niemann-Pick A disease (NPA) is a fatal lysosomal storage disorder caused by a deficiency in acid sphingomyelinase (ASM) activity. The lack of functional ASM results in cellular accumulation of sphingomyelin and cholesterol within distended lysosomes throughout the brain. In this study, we investigated the potential of AAV-mediated expression of ASM to correct the brain pathology in an ASM knockout (ASMKO) mouse model of NPA. An AAV serotype 2 vector encoding human ASM (AAV2-hASM) was injected directly into the adult ASMKO hippocampus of one hemisphere. This resulted in expression of human ASM in all major cell layers of the ipsilateral hippocampus for at least 15 weeks postinjection. Transduced cells were also present in the entorhinal cortex, medial septum, and contralateral hippocampus in a pattern consistent with retrograde axonal transport of AAV2. There was a substantial reduction of distended lysosomes and an almost complete reversal of cholesterol accumulation in all areas of the brain that were targeted by AAV2-hASM. These findings show that the ASMKO brain is responsive to ASM replacement and that retrograde transport of AAV2 functions as a platform for widespread gene delivery and reversal of pathology in affected brain.
Mol Ther 2005 May
PMID:AAV vector-mediated correction of brain pathology in a mouse model of Niemann-Pick A disease. 1585 Oct 14


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