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)

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

The Niemann Pick-C1 (NPC-1) protein is essential for intracellular transport of cholesterol derived from low-density lipoprotein import in mammalian cells. The role of the protein kinase A (PKA) pathway in regulation of expression of the NPC-1 gene was investigated. NPC-1 promoter activity was induced by treatment with dibutryl cAMP (dbcAMP), alone or in combination with the cAMP response element (CRE) binding protein (CREB) overexpressed in adrenal Y-1 cells. When the catalytic subunit of PKA was overexpressed in Y-1 cells, there were similar increases in NPC-1 promoter activity in the presence of CREB. Responses were attenuated by blockade of the PKA pathway, and in the Kin-8 cell line deficient in PKA. Promoter deletion analysis revealed that this response was present in promoter fragments of 186 bp and larger but not present in the 121-bp fragment. Two promoter regions, one at -430 and one at -120 upstream of the translation initiation site, contained CRE consensus sequences. These bound recombinant CREB in EMSA, confirming their authenticity as CREB response elements. Promoters bearing mutations of both CRE displayed no response to dbcAMP. The orphan nuclear receptor, steroidogenic factor-1 (SF-1), was implicated in NPC-1 transactivation by the presence of SF-1 target sequence that formed a complex with recombinant SF-1 in EMSA. Furthermore, transfection of a plasmid that overexpressed SF-1 into ovarian granulosa cells increased promoter activity in response to dbcAMP, an effect abrogated by mutation of the SF-1 target sequence. Chromatin immunoprecipitation assays demonstrated that the CRE region of the endogenous and transfected NPC-1 promoter associated with both acetylated and phosphorylated histone H-3 and that this association was increased by dbcAMP treatment. Treatment with dbcAMP also increased the association of the CRE region of the promoter with CREB binding protein, which has histone acetyltransferase activity. Together, these results demonstrate a mechanism of regulation of NPC-1 expression by the cAMP-PKA pathway that includes PKA phosphorylation of CREB, recruitment of the coactivator CREB binding protein and the phosphorylation and acetylation of histone H-3 to transactivate the NPC-1 promoter.
Mol Endocrinol 2003 Apr
PMID:Regulation of niemann-pick c1 gene expression by the 3'5'-cyclic adenosine monophosphate pathway in steroidogenic cells. 1255 81

We have recently shown that the inflammatory process during experimental allergic encephalomyelitis (EAE), the animal model of MS, attracts transplanted NPC migration into the inflamed white matter. Here we studied how the proinflammatory cytokines tumor necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma) affect NPC growth, survival, differentiation, and migration. Newborn rat striatal NPCs were expanded in spheres as nestin+, PSA-NCAM+, NG2(-) cells, which differentiated into astrocytes, oligodendrocytes, and neurons. NPCs expressed receptors of TNFalpha and IFNgamma but not interleukin-1. TNFalpha and IFNgamma inhibited sphere cell proliferation, determined by [(3)H]thymidine and BrdU incorporation. IFNgamma increased apoptotic cell death (determined by TUNEL stains); this effect partially blocked by TNFalpha. Neither cytokine affected NPC lineage fate, determined by percentage of GFAP+, neurofilament+, and GalC+ cells after differentiation. TNFalpha and IFNgamma increased outward migration of cells from spheres in vitro. Thus, TNFalpha and IFNgamma, key players in MS and EAE, inhibit NPC proliferation and induce their migration.
Mol Cell Neurosci 2003 Nov
PMID:Effects of proinflammatory cytokines on the growth, fate, and motility of multipotential neural precursor cells. 1466 13

Despite the apparent overall structural stability of the nuclear pore complex during interphase, at least two nucleoporins have been shown to move dynamically on and off the pore. It is not yet certain what contribution nucleoporin mobility makes to the process of nuclear transport or how such mobility is regulated. Previously, we showed that Nup98 dynamically interacts with the NPC as well as bodies within the nucleus in a transcription-dependent manner. We have extended our studies of dynamics to include Nup153, another mobile nucleoporin implicated in RNA export. In both cases, we found that although only one domain is essential for NPC localization, other regions of the protein significantly affect the stability of association with the pore. Interestingly, like Nup98, the exchange of Nup153 on and off the pore is inhibited when transcription by Pol I and Pol II is blocked. We have mapped the regions required to link Nup98 and Nup153 mobility to transcription and found that the requirements differ depending on which polymerases are inhibited. Our data support a model whereby transcription of RNA is coupled to nucleoporin mobility, perhaps ultimately linking transport of RNAs to a cycle of remodeling at the nuclear pore basket.
Mol Biol Cell 2004 Apr
PMID:Distinct functional domains within nucleoporins Nup153 and Nup98 mediate transcription-dependent mobility. 1471 58

Cholesterol is imported and processed to provide substrate for ovarian steroidogenesis. The Niemann Pick type C-1 gene codes for a glycoprotein that processes low-density lipoproteinimported cholesterol. Mutation of this gene causes marked impairment of export of low-density lipoprotein-derived cholesterol from endosomes, and consequent lysosomal accumulation of the sterol. The BALB/c npc(nih-/-) mouse line, bearing spontaneous mutation of the NPC-1 gene, provides a model for investigation of aberrant endosomal cholesterol transfer in the ovary. Female homozygote mutant mice are infertile, with underdeveloped ovarian follicles, reduced steroidogenesis, no ovulation, and no corpora lutea. Mutant ovaries transplanted under wild-type kidney capsules display both ovulation and formation of corpora lutea. Gonadotropin treatment induces ovulation and restores expression of steroidogenic proteins. Pituitary glands of mutants are hypoplastic, and prolactin expression is dramatically reduced compared with wild-type mice. Both long and short splice variants of the dopamine-D2 receptors are overexpressed in the pituitary of BALB/c npc(nih-/-) mice. Chronic treatment of mutant mice with 17beta-estradiol restores pituitary volume, prolactin expression, and folliculogenetic capability. We conclude that inactivating mutation of Niemann Pick C-1 perturbs the hypothalamic-pituitary-ovarian feedback loop. Reduced estrogens attenuate prolactin expression and alter gonadotropin secretion patterns and interfere with normal ovarian follicular development and ovulation.
Mol Endocrinol 2004 Jul
PMID:Aberrant intracellular cholesterol transport disrupts pituitary and ovarian function. 1510 38

Mice double deficient in LAMP-1 and -2 were generated. The embryos died between embryonic days 14.5 and 16.5. An accumulation of autophagic vacuoles was detected in many tissues including endothelial cells and Schwann cells. Fibroblast cell lines derived from the double-deficient embryos accumulated autophagic vacuoles and the autophagy protein LC3II after amino acid starvation. Lysosomal vesicles were larger and more peripherally distributed and showed a lower specific density in Percoll gradients in double deficient when compared with control cells. Lysosomal enzyme activities, cathepsin D processing and mannose-6-phosphate receptor expression levels were not affected by the deficiency of both LAMPs. Surprisingly, LAMP-1 and -2 deficiencies did not affect long-lived protein degradation rates, including proteolysis due to chaperone-mediated autophagy. The LAMP-1/2 double-deficient cells and, to a lesser extent, LAMP-2 single-deficient cells showed an accumulation of unesterified cholesterol in endo/lysosomal, rab7, and NPC1 positive compartments as well as reduced amounts of lipid droplets. The cholesterol accumulation in LAMP-1/2 double-deficient cells could be rescued by overexpression of murine LAMP-2a, but not by LAMP-1, highlighting the more prominent role of LAMP-2. Taken together these findings indicate partially overlapping functions for LAMP-1 and -2 in lysosome biogenesis, autophagy, and cholesterol homeostasis.
Mol Biol Cell 2004 Jul
PMID:Disturbed cholesterol traffic but normal proteolytic function in LAMP-1/LAMP-2 double-deficient fibroblasts. 1512 81

Niemann-Pick disease type C (NPC), a neurovisceral disorder characterized by accumulation of cholesterol and glycolipids in the lysosomal/late endosomal system, is due to mutations on either the NPC1 or the NPC2 genes. Although NPC1 and NPC2 proteins appear essential for proper cellular cholesterol trafficking, their precise functions and relationship have remained elusive. Mutation identification in NPC2 patients did not provide insights into structure-function relationships, but recent studies brought important information on the cholesterol-binding site of the NPC2 protein. The present work was focused on localization and N-glycosylation of NPC2, considering that glycosylation is often essential for targeting, stability and biological function of proteins. Using immunocytofluorescence in cultured human fibroblasts, we found that the native NPC2 protein is essentially lysosomal, at variance with the late endosomal location of NPC1. Expression of cDNA mutants affecting each of the three potential NPC2 N-glycosylation sites in NPC2-/- fibroblasts showed that only two sites are used. The intracellular human NPC2 protein occurred as two N-glycosylated forms, with either one single oligosaccharide chain attached to Asn 58 or two oligosaccharides attached to Asn 58 and 135. The oligosaccharidic chains were of the hybrid and/or high mannose type, with no complex chains. Further studies on the cellular location of Asn 58 and Asn 135 mutant proteins and their respective effect on restoration of normal cholesterol traficking in NPC2-/- cells led to the conclusion that only the oligosaccharide chain carried by Asn 58 is responsible for proper targeting of NPC2 to lysosomes, and is crucial for NPC2 function.
Mol Genet Metab 2004 Nov
PMID:Niemann-Pick type C disease: importance of N-glycosylation sites for function and cellular location of the NPC2 protein. 1554 93

Niemann-Pick disease type C (NP-C) is an autosomal recessive neurovisceral storage disease with neurodegeneration caused by mutations in either the NPC-1 or NPC-2 gene. The murine ortholog of NPC-1 is mutated in BALB/c npc(nih) and this mutant mouse shows equally conspicuous neurodegeneration and loss of neurons. However, the molecular mechanisms causing neurodegeneration in NP-C remain elusive. Here, we report the presence of apoptotic cells detected by both TUNEL staining and electron microscopy in the cerebrum and cerebellum of human patients and the mouse model. Moreover, we found that with progression of the disease process leading to neuronal cell death, an up-regulation of genes involved in the TNF-alpha death pathway caspase-8, FADD, TNFRp55, TRADD, and RIP-by an RNA protection assay. Furthermore, RT-PCR showed that TNF-alpha mRNA expression level also increased up to 30-50-fold in the cerebellum of 7- and 9-week-old NP-C mice compared with wild-type mice. Elevated expression of TNF-alpha was detected in both neurons and astrocytes with TNF-alpha-expressing astrocytes distributed in the affected brain regions. Collectively, our results suggest that the cell death in the brain of NP-C disease occurs through apoptosis and it is mediated by the TNF receptor superfamily pathway.
Mol Genet Metab 2005 Jan
PMID:Apoptosis accompanied by up-regulation of TNF-alpha death pathway genes in the brain of Niemann-Pick type C disease. 1563 90

Niemann-Pick disease type C (NPC), a neurovisceral disorder characterized by accumulation of unesterified cholesterol and glycolipids in the lysosomal/late endosomal system, is due to mutations on either the NPC1 or the NPC2 genes. While the corresponding proteins appear essential for proper cellular cholesterol trafficking, their precise function and relationship are still unclear. Mutational analysis of patients, useful for the study of structure/function relationships, is especially valuable for proper management of affected families. Correlations have been found between genotypes and the severity of the neurological outcome of the patients, and molecular genetics constitutes the optimal approach for prenatal diagnosis. However, mutation detection in NPC disease is a challenge. The NPC1 gene, affected in >95% of the families, is large in size (approximately 50 kb), and the already known disease-causing mutations and numerous polymorphisms are scattered over 25 exons. Furthermore, detection of NPC2 patients by complex genetic complementation tests is unpractical. In the present study, we describe a rapid and reliable strategy for detecting NPC genetic variations using DHPLC analysis. Conditions of analysis were optimized for all the NPC1 and NPC2 30 exons and validated using 38 previously genotyped patients. These conditions were then applied to screen a panel of 35 genetically uncharacterized, unrelated NPC patients. Pathogenic mutations were identified in 68/70 alleles. Among the mutations identified, 29 were novel, including two of the NPC2 gene. We conclude that DHPLC is a rapid, low-cost, highly accurate, and efficient technique for the detection of NPC genetic variants.
Mol Genet Metab
PMID:Niemann-Pick C disease: use of denaturing high performance liquid chromatography for the detection of NPC1 and NPC2 genetic variations and impact on management of patients and families. 1612 23

Niemann-Pick type C (NPC) disease is an inherited lipid storage disorder characterized by the lysosomal accumulation of free cholesterol in affected cells. Three novel mutations in the NPC1 gene (c.3615delA, c.2000C > T, and c.2240delT) were detected in two unrelated patients with the severe phenotype of NPC. The analyses showed that the c.2240delT mutation, which causes a premature stop at codon 748, resulted in nonsense-mediated decay of the mutant transcripts. Immunoblotting analyses for the NPC1 protein did not detect the mutant proteins in COS-1 cells transiently transfected with the two mutant NPC1 cDNA constructs (c.3615delA and c.2000C > T). In NPC cells, sphingomyelin accumulates with cholesterol, leading to an identical subcellular distribution of both lipids. Acid sphingomyelinase (ASM), which is responsible for the lysosomal hydrolysis of sphingomyelin, is partially reduced in NPC fibroblasts. Therefore, NPC fibroblasts were studied to determine if ASM activity was perturbed due to the accumulation of cholesterol. However, these studies demonstrated that the subcellular localization of ASM was preserved, suggesting that the high content of lysosomal cholesterol was not responsible for the decreased ASM activity.
Mol Genet Metab 2006 Feb
PMID:Niemann-Pick type C disease: novel NPC1 mutations and characterization of the concomitant acid sphingomyelinase deficiency. 1614 56


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