Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Filipin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 631 records · Page 35Linked to original sources
PubMed1994

Regulation of intracellular cholesterol metabolism is defective in lymphoblasts from Niemann-Pick type C and type D patients.

Regulation of intracellular cholesterol metabolism has been studied in Epstein-Barr virus-transformed lymphoblasts from patients with Niemann-Pick type C (NPC) and the Nova Scotia type D (NPD) disease. Addition of LDL to normal lymphoblasts cultured in lipoprotein-deficient medium increased cholesterol esterification 10-fold (to a maximum of 1.0 nmol/h/mg protein at 15 h), while little stimulation was seen in NPC cells. The response by NPD lymphoblasts was intermediate, reaching approximately half of normal values by 14-24 h. Lymphoblasts from both NPC and NPD obligate heterozygotes exhibited 50% of normal LDL-stimulated cholesterol esterification at 6 h, when activity was < 10% of normal values in patient cells. Fluorescence staining with filipin indicated excessive intracellular accumulation of LDL-derived cholesterol in both NPC and NPD lymphoblasts. Downregulation of LDL receptor mRNA levels by LDL, measured by S1 nuclease protection assay, was also impaired in NP lymphoblasts and fibroblasts (NPC > NPD), although a similar rate of receptor protein down-regulation by LDL (t1/2 = 10-15 h) was observed in normal and NP lymphoblasts. In contrast, LDL down-regulation of 3-hydroxy-3-methylglutaryl-CoA reductase mRNA did not appear to be affected in NP cells: LDL produced a 3-fold (lymphoblasts) or > 10-fold (fibroblasts) decrease by 12 h in both normal and affected cells. Thus, NPC and NPD lymphoblasts exhibit distinct defects in cholesterol esterification and storage, similar to those observed in mutant fibroblasts. Other regulatory responses are also impaired in NPC lymphoblasts but appear to be less affected in NPD cells. Lymphoblasts should provide a valuable immortalized cell line model for study of defective regulation of cholesterol esterification and transport in Niemann-Pick type II disease, and may also be suitable for diagnosis and carrier detection.

Cholesterol↗
PubMed2004

Perfringolysin O, a cholesterol-binding cytolysin, as a probe for lipid rafts.

Gaining an understanding of the structural and functional roles of cholesterol in membrane lipid rafts is a critical issue in studies on cellular signaling and because of the possible involvement of lipid rafts in various diseases. We have focused on the potential of perfringolysin O (theta-toxin), a cholesterol-binding cytolysin produced by Clostridium perfringens, as a probe for studies on membrane cholesterol. We prepared a protease-nicked and biotinylated derivative of perfringolysin O (BCtheta) that binds selectively to cholesterol in cholesterol-rich microdomains of cell membranes without causing membrane lesions. Since the domains fulfill the criteria of lipid rafts, BCtheta can be used to detect cholesterol-rich lipid rafts. This is in marked contrast to filipin, another cholesterol-binding reagent, which binds indiscriminately to cell cholesterol. Using BCtheta, we are now searching for molecules that localize specifically in cholesterol-rich lipid rafts. Recently, we demonstrated that the C-terminal domain of perfringolysin O, domain 4 (D4), possesses the same binding characteristics as BCtheta. BIAcore analysis showed that D4 binds specifically to cholesterol with the same binding affinity as the full-size toxin. Cell-bound D4 is recovered predominantly from detergent-insoluble, low-density membrane fractions where raft markers, such as cholesterol, flotillin and Src family kinases, are enriched, indicating that D4 also binds selectively to lipid rafts. Furthermore, a green fluorescent protein-D4 fusion protein (GFP-D4) was revealed to be useful for real-time monitoring of cholesterol in lipid rafts in the plasma membrane. In addition, the expression of GFP-D4 in the cytoplasm might allow the investigations of intracellular trafficking of lipid rafts. The simultaneous visualization of lipid rafts in plasma membranes and inside cells might help in gaining a total understanding of the dynamic behavior of lipid rafts.

Journal Article↗
PubMed2004

Human ATP-binding cassette transporter-2 (ABCA2) positively regulates low-density lipoprotein receptor expression and negatively regulates cholesterol esterification in Chinese hamster ovary cells.

We present evidence that the ATP binding-cassette transporter-2 (ABCA2) is a sterol-responsive gene that has a role in the trafficking of low-density lipoprotein-derived free cholesterol (LDL-FC). In HepG2 cells ABCA2 was coordinately expressed with other sterol-responsive genes. Stable constitutive expression of ABCA2 in Chinese hamster ovary cells (CHOA2) was accompanied by an increase the expression of the low-density lipoprotein receptor (LDLR) and other genes involved in the regulation of cholesterol homeostasis. LDLR mRNA was elevated greater than ninefold and 3-hydroxy-3-methylglutaryl CoA synthase (HMGCoA S) expression was elevated sevenfold in CHOA2 cells. The increase in LDLR expression was regulated at the level of transcription; however, culture of CHO and CHOA2 cells in medium containing lipoprotein-deficient serum (LPDS) results in similar levels of LDLR promoter expression. No differences were measured in the dose-dependent uptake of fluorescently labeled 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchorate-LDL (DiI-LDL) between CHO and CHOA2 cells cultured in medium containing LPDS. Ultraviolet microscopy revealed a similar distribution of the DiI-LDL label in cytoplasmic vesicles. We measured an LDL dose-dependent reduction in esterification of LDL-FC in intact CHOA2 cells cultured in medium containing LPDS, however, no significant difference was measured in acylcoenzyme A:cholesterol acyltransferase (ACAT) activity in cell-free extracts of CHO and CHOA2 cells. CHO cells or CHOA2 cells treated with the hydrophobic amine, U18666A, showed similar filipin staining of unesterified cholesterol in cytoplasmic vesicles. Addition of progesterone or U18666A to CHO cells elevated ABCA2 expression. Finally, we found that ABCA2 expression was elevated in Niemann-Pick type C1 (NPC1) fibroblasts and in Familial Hypercholesterolemia (FHC) fibroblasts.

ATP-Binding Cassette Transporters↗
PubMed2005

Membrane-anchored CD14 is required for LPS-induced TLR4 endocytosis in TLR4/MD-2/CD14 overexpressing CHO cells.

Lipopolysaccharide (LPS) induces inflammatory activation through TLR4 (toll-like receptor-4)/MD-2 (myeloid differentiation-2)/CD14 (cluster of differentiation-14) complex. Although optimal LPS signaling is required to activate our innate immune systems against gram-negative bacterium, excessive amount of LPS signaling develops a detrimental inflammatory response in gram-negative bacterial infections. Downregulation of surface TLR4 expression is one of the critical mechanisms that can restrict LPS signaling. Here, we found that membrane-anchored CD14 is required for LPS-induced downregulation of TLR4 and MD-2 in CHO cells. Moreover, pretreatment of the cells with sterol-binding agent filipin reduced LPS-induced TLR4 downregulation, suggesting the involvement of caveolae-mediated endocytosis pathway. Involvement of caveolae in LPS-induced TLR4 endocytosis was further confirmed by immunoprecipitation. Thus, our data indicate that caveolae-dependent endocytosis pathway is involved in LPS-induced TLR4 downregulation and that this is dependent on membrane-anchored CD14 expression.

Animals↗
PubMed2004

Up-regulation of low-density lipoprotein receptor in human hepatocytes is induced by sequestration of free cholesterol in the endosomal/lysosomal compartment.

Up-regulation of low-density lipoprotein receptor (LDLr) is a key mechanism to control elevated plasma LDL-cholesterol levels. In the present paper, we compare the ability of four distinct pharmacological drugs to up-regulate LDLr expression in human hepatocytes. HepG2 cells were treated with the steroidal analog GW707, the oxidosqualene cyclase inhibitor U18666A, the 3beta-hydroxysterol Delta(7)-reductase inhibitor AY-9944 and the vacuolar-type ATPase inhibitor bafilomycin A1. We found that the four compounds induced sequestration of free cholesterol in the endosomal/lysosomal compartment leading to a positive filipin staining pattern and a complete inhibition of cholesteryl ester synthesis. As a consequence of the sequestration of cholesterol, the expression and the activity of LDLr were strongly induced resulting from a transcriptional effect which was measured by a reporter gene assay. These effects were fully abolished when an exogenous water soluble cholesterol analog was added to the cells. These findings have led to the identification of a common mechanism to up-regulate LDLr expression in human hepatocytes and may represent an interesting alternative approach to identify new hypolipidemic drugs.

Androstenes↗
PubMed2004

Synergistic upregulation of low-density lipoprotein receptor activity by tamoxifen and lovastatin.

OBJECTIVE: To study the mechanism involved in the cholesterol-lowering activity of tamoxifen, an estrogen receptor (ER) modulator widely used in breast cancer therapy. METHODS AND RESULTS: We used MOLT-4 cells, which do not express estrogen receptors and require important amounts of cholesterol for proliferation. We firstly confirmed that tamoxifen reduced cholesterol biosynthesis by inhibiting sterol Delta(8,7)-isomerase and Delta(24)-reductase activities, which resulted in the accumulation of zymosterol. In cells incubated in the presence of low-density lipoprotein (LDL) (120 microg cholesterol/ml), tamoxifen stimulated LDL receptor activity and expression in a dose-dependent manner, as determined by 1,1'-dioctadecyl-3,3,3,3'-tetramethylindocarbocyanineperchlorate (DiI)-labeled LDL uptake, LDL receptor expression on the cell surface and LDL receptor mRNA levels. Furthermore, tamoxifen, but not lovastatin, inhibited the egress of LDL-derived cholesterol from lysosomes, as ascertained by filipin staining in both MOLT-4 and HepG2 cells. When studied in combination, especially at relatively high LDL concentrations in the medium, tamoxifen and lovastatin stimulated LDL receptor activity synergistically, which is attributed to the different mechanism of action these drugs exhibit. CONCLUSIONS: The present study demonstrates the stimulation of the LDL receptor by tamoxifen. These results explain the long-known hypolipidemic effect of tamoxifen and support its use, or that of other intracellular cholesterol trafficking inhibitors, in combination with statins for the reduction of plasma LDL cholesterol levels.

Cell Line, Tumor↗
PubMed2006

Structural and immunocytochemical alterations in eye lens fiber cells from Cx46 and Cx50 knockout mice.

In the current study we describe the changes of overall organization of lens fiber cells in connexin 46 (Cx46) and connexin 50 (Cx50) knockout mice. Morphometric analyses and the application of immunocytochemical techniques revealed that in Cx46 knockout lens (Cx46 -/-), where Cx50 is expressed alone, the postnatal differentiation of secondary fiber cells proceeds faster and is characterized by an increased number of smaller fiber cells. Conversely, in Cx50 knockout mice (Cx50 -/-), the lenticular mass is considerably reduced and characterized by a small number of fiber cells added during the postnatal period. The process of terminal differentiation was impaired and generated larger fiber cells still possessing cytoplasmic organelles. Freeze-fracture and fracture labeling revealed that the junctional assembly, packing organization and topographic interactions between connexons and MP26 differed when Cx46 and Cx50 were co-assembled in the wild-type or expressed separately in the two distinct knockout phenotypes. Filipin cytochemistry provided indirect evidence that Cx46 and Cx50 expressed alone are recruited into different lipid environments. Our results represent the structural proof that interaction of connexins and MP26 contributes to the overall organization of the fiber cells.

Animals↗
PubMed2006

Efficient gene transfer by pullulan-spermine occurs through both clathrin- and raft/caveolae-dependent mechanisms.

The feasibility and mechanism of gene delivery by pullulan-spermine, a recently developed cationic polysaccharide, were investigated. Pullulan-spermine-mediated transfection of plasmid DNA resulted in greatly reduced cytotoxicity and a 10-fold increase in the level of gene expression when compared to Lipofectamine 2000, a commercially available cationic lipid. Additionally, after transfection of p53-expressing plasmid DNA by pullulan-spermine but not Lipofectamine 2000, the in vitro proliferation of T24 cells was significantly reduced. Pullulan-spermine-mediated gene expression was inhibited by both chlorpromazine of clathrin-mediated endocytosis inhibitor and methyl-beta-cyclodextrin and filipin of raft/caveolae inhibitors. We conclude that pullulan-spermine is a promising carrier for gene transfection, and that cellular uptake of pullulan-spermine-plasmid DNA complexes is mediated by clathrin- and raft/caveolae-dependent endocytotic pathways.

Asialoglycoprotein Receptor↗
PubMed2006

Gene delivery by dendrimers operates via different pathways in different cells, but is enhanced by the presence of caveolin.

In order to optimise and improve the efficacy of transfection mediated by dendrimers, it is essential to fully understand the mechanisms of cell entry and intracellular trafficking by these complexes. Previously, we have shown that gene delivery by dendrimers is dependent from cholesterol and membrane rafts. The inhibition of transfection by treatment with filipin III suggested that gene delivery might be occurring by a caveolin-dependent pathway. We therefore investigated the internalisation and transfection properties of dendriplexes using cell lines (HeLa and HepG2) that express few caveolae. We show that, in contrast to other cells, cholesterol depletion does not affect the ability of dendriplexes to transfect these cells. Inhibition of clathrin-independent, phagocytic and macropinocytic pathways also failed to inhibit transfection of these cells and endothelial cells. However, overexpression of caveolin 1 resulted in an increased rate of dendriplex uptake into HeLa, HepG2 and endothelial cells, and increased transfection efficiency. Furthermore, in endothelial cells, confocal microscopy demonstrated colocalisation of dendriplexes and caveolin 1. These data highlight that dendriplexes may use different internalisation pathways in different cells, and that caveolae form a preferential route for gene delivery by this non-viral vector.

Androstadienes↗
PubMed2004

Molecular diffusion in sperm plasma membranes during epididymal maturation.

Fluorescence recovery after photobleaching (FRAP) analysis has been used to measure lipid diffusion in different regions of the sperm plasma membrane. Our goal has been to understand how some membrane components are confined to specific surface domains, whilst others are freely diffusing and in some cases are able to migrate against large concentration gradients. Results with a variety of fluorescent lipid reporter probes (ODAF, NBD-PC, NBD-cholesterol) show that diffusion coefficients (D) are generally three to four times higher on the sperm acrosome than on the principal piece of the tail and increase significantly during epididymal maturation (ram, mouse, goat, dog and monkey sperm). Cholesterol diffusion is approximately 10 times faster on the sperm head than the tail and has a heterogenous distribution when detected with filipin. Lipid diffusion is very temperature sensitive but remarkably insensitive to changes in external pH and osmotic pressure. There was no evidence that the posterior ring or annulus functioned as diffusion barriers to lipids. On this basis it was possible to construct models of increasing complexity to describe the behaviour of a lipid molecule on the sperm surface, beginning with simple linear diffusion progressing to random diffusion and eventually to constrained diffusion.

Animals↗
PubMed2006

The internalization route resulting in successful gene expression depends on both cell line and polyethylenimine polyplex type.

Understanding cellular uptake and intracellular processing of nonviral gene delivery systems is a key aspect in developing more efficient vectors. In this study, the impact of clathrin- and caveolae/lipid-raft-dependent endocytosis on cell entry and overall transfection efficiency of polyethylenimine (PEI) polyplexes was evaluated. Most remarkably, the internalization pathway mediating successful transfection depended on both cell type and polyplex type applied. Colocalization studies with transferrin and cholera toxin B revealed that at least two specific endocytosis pathways--the clathrin-dependent and the lipid-raft-dependent--mediated cellular uptake of PEI polyplexes. With the help of specific uptake inhibitors (chlorpromazine and filipin III), cell-line-dependent variations regarding the route of successful transfection were observed (HUH-7, COS-7, HeLa). In COS-7 cells, the clathrin-dependent pathway was the main contributor to the transfection process. In HUH-7 cells, gene transfer by linear PEI polyplexes succeeded mainly via the clathrin-dependent route, whereas transfection by branched PEI polyplexes was mediated by both pathways. In HeLa cells, both pathways were able to mediate successful gene delivery. However, the lipid-raft-dependent pathway was more relevant. The study also revealed that the concentration window between specific inhibitory function and nonspecific toxicity of the uptake inhibitors was very narrow.

Animals↗
PubMed2003

Apolipoprotein B in cholesterol-containing drusen and basal deposits of human eyes with age-related maculopathy.

Lipids accumulate in Bruch's membrane (BrM), a specialized vascular intima of the eye, and in extracellular lesions associated with aging and age-related maculopathy (ARM). We tested the hypothesis that ARM and atherosclerotic cardiovascular disease share molecules and mechanisms pertaining to extracellular lipid accumulation by localizing cholesterol and apolipoprotein B (apo B) in BrM, basal deposits, and drusen. Human donor eyes were preserved <4 hours postmortem and cryosectioned. Sections were stained with traditional lipid stains and filipin for esterified and unesterified cholesterol or probed with antibodies to apo B, apo E, and apo C-III. Normal adult retinal pigment epithelium (RPE) was subjected to RT-PCR and Western blot analysis for apolipoprotein mRNA and protein. Esterified and unesterified cholesterol was present in all drusen and basal deposits of ARM and normal eyes. Both apo B and apo E but not apo C-III were found in BrM, drusen, and basal deposits. Fewer macular drusen were stained by traditional lipid stains and apolipoprotein antibodies than peripheral drusen. RPE contained apo B and apo E mRNA and protein. Finding cholesterol and apo B in sub-RPE deposits links ARM with important molecules and mechanisms in atherosclerosis initiation and progression. The combination of apo B mRNA and protein in RPE raises the possibility that intraocular assembly of apo B-containing lipoproteins is a pathway involved in forming cholesterol-enriched lesions in ARM.

Adult↗
PubMed1998

Cholesterol-dependent generation of a unique amyloid beta-protein from apically missorted amyloid precursor protein in MDCK cells.

To investigate the implications of altered sorting of the beta-amyloid precursor protein (betaAPP) in the abnormal generation of amyloid beta-protein (Abeta), we characterized Abeta secreted from Madin-Darby canine kidney (MDCK) cells which had been stably transfected with a cDNA encoding the human beta-amyloid precursor protein (betaAPP695) with a 42 amino acid residue truncation at the carboxyl terminus (DeltaC). In DeltaC MDCK cells, the intracellular sorting of betaAPP is substantially altered to the apical surface. We detected an accumulation of a unique Abeta species in the apical compartment of DeltaC MDCK cell cultures. This unique Abeta was immunoprecipitated with 4G8 (a monoclonal antibody specific for Abeta17-24) and detected as a smear on Western blots, but was not immunoprecipitated with BAN50 (a monoclonal antibody raised against Abeta1-16). Interestingly, however, this Abeta species was readily immunoprecipitated with BAN50 upon treatment with formic acid. Furthermore, incubation of the DeltaC MDCK cells with compactin, an inhibitor of de novo cholesterol synthesis, or with filipin, a cholesterol-binding drug, resulted in marked changes in the characteristics of this Abeta species as follows: first, the Abeta was not observed as a smear on Western blots and second, the Abeta was immunoprecipitated with BAN50. The present results strongly suggest that an Abeta with unique molecular characteristics is generated from the missorted betaAPP in vivo in a cholesterol-dependent manner.

Alzheimer Disease↗
PubMed1997

HDL3-signalling in HepG2 cells involves glycosyl-phosphatidylinositol-anchored proteins.

In [3H]phosphatidylcholine (PC) prelabelled HepG2 cells, HDL3 stimulates a biphasic increase in 1.2-diacylglycerol (DAG). The early phase is mediated in part by a phospholipase C which is inhibited by 10 microM D 609, RHC-80267 or U-73122 and less by 100 microM propranolol. A phospholipase D is more likely involved in the late phase, as the DAG peak lags behind phosphatidic acid rise and is blocked by 100 microM propranolol. Cellular preincubation with 200 microg/ml antibodies against the inositolphosphoglycan (IPG) moiety of the GPI-anchor (Ab(IPG)), or depletion in GPI-anchored proteins by cellular pretreatment with 0.5 U/ml PI-PLC, 1 mM insulin and 2 HU/ml streptolysin-O, or depletion in membrane cholesterol content by filipin (5 microg/ml), digitonin (5 microg/ml) and cholesterol oxidase (0.5 U/ml) decreases the HDL3-signal, suggesting the involvement of a lipolytic cleavage of GPI-anchored proteins. Inhibition of proteases by 1 mM leupeptin/PMSF improves the response time to HDL3, with a DAG peak at 2-3 min. In the presence of protease-inhibitors, HDL3 releases in the culture medium several proteins with a residual IPG that binds Ab(IPG) after SDS-PAGE analysis and immunoblotting. HDL3-signalling pathways comprise tyrosine kinases, as preincubation with 100 microg/ml genistein or tyrphostin inhibits the HDL3-signal. HDL3 activates PC hydrolysis through a multistep pathway involving the cleavage of GPI-anchored proteins.

Antibodies↗
PubMed2003

Cytochrome p450 complement (CYPome) of the avermectin-producer Streptomyces avermitilis and comparison to that of Streptomyces coelicolor A3(2).

The genus Streptomyces produces about two-thirds of naturally occurring antibiotics and a wide array of other secondary metabolites, including antihelminthic agents, antitumor agents, antifungal agents, and herbicides. The newly completed genome sequence of the avermectin-producing bacterium Streptomyces avermitilis contains 33 cytochromes p450 (CYPs), many more than the 18 observed in Streptomyces coelicolor A3(2). Some of the likely metabolic functions are reported together with their genomic location and bioinformatic analysis. Seven entirely new CYP families were found together with close homologues of some forms observed in S. coelicolor A3(2). The presence of unusual CYP forms associated with conservons is revealed and of these, CYP157 forms in both S. avermitilis and S. coelicolor A3(2) deviate from the previously accepted rule for an EXXR motif within the K-helix of CYPs. Amongst this range of CYPs are forms associated with avermectin, filipin, geosmin, and pentalenolactone biosynthesis as well as unknown pathways of secondary metabolism.

Chromosomes, Fungal↗
PubMed1999

Inhibition of cholesteryl ester formation in macrophages by azole antimycotics.

Cultured macrophages take up and metabolize cholesterol-containing liposomes, resulting in massive accumulation of cholesteryl esters in the cells. Using this system, the effects of azole antimycotics on cholesteryl ester formation were studied. Incubation of mouse peritoneal macrophages with ketoconazole, miconazole, or econazole (0.1-10 microM) resulted in concentration-dependent inhibition of cholesteryl ester synthesis from endocytosed cholesterol. IC50 values (concentration resulting in 50% inhibition) were 1.4 +/- 0.1 microM, 4.1 +/- 0.2 microM, and 3.6 +/- 0.2 microM for ketoconazole, miconazole, and econazole, respectively. Complete inhibition was observed with 10 microM ketoconazole, and miconazole and econazole, each at 10 microM, caused 70 and 75% inhibition, respectively, of cholesteryl ester synthesis. The mechanism underlying the inhibition by ketoconazole was further studied. Ketoconazole did not appreciably block the uptake of liposomes or formation of triacylglycerol up to 10 microM. Interestingly, ketoconazole suppressed only 30% of 25-hydroxycholesterol-induced endogenous cholesterol esterification under conditions where esterification of endocytosed cholesterol was completely inhibited. Cytochemical studies with filipin-cholesterol staining revealed that ketoconazole induced massive accumulation of endocytosed cholesterol in macrophage phagolysosomes. These results indicate that ketoconazole inhibits cholesteryl ester formation in macrophages by blocking the intracellular transport of endocytosed cholesterol from lysosomes to the endoplasmic reticulum.

Animals↗
PubMed2002

Internalization of pancreatic polypeptide Y4 receptors: correlation of receptor intake and affinity.

Unlike neuropeptide Y receptors, the pancreatic polypeptide Y4 receptors display considerable differences in sequence and ligand-binding affinity across mammalian species. This could produce different receptor turnover rates in the same cellular membrane environment. Comparing rat, human and guinea-pig Y4 receptors expressed in Chinese hamster ovary (CHO) cells (K(d) with human pancreatic polypeptide 14, 45 and 116 pM, respectively), we indeed found human pancreatic polypeptide internalization in the rank order of receptor affinities. A large fraction of the internalized human pancreatic polypeptide, similar across the Y4 species, was associated with secondary endosomes (density approximately 1.05 in Percoll gradients) and lysosomes (density approximately 1.11). For all Y4 receptors examined, this intake was potently and selectively inhibited by cholesterol-complexing polyene antibiotic filipin III and also by clathrin lattice formation inhibitor, phenylarsine oxide. Internalization differences found across Y4 receptor species to a degree compare with those observed for the cloned guinea-pig neuropeptide Y Y1 and human neuropeptide Y Y5 receptors and, generally, support ligand-binding affinities as important determinants of internalization for neuropeptide receptors.

Animals↗
PubMed2003

Concurrent increase of cholesterol, sphingomyelin and glucosylceramide in the spleen from non-neurologic Niemann-Pick type C patients but also patients possibly affected with other lipid trafficking disorders.

Niemann-Pick type C disease (NPC) is a neurovisceral (or, extremely rarely, only visceral) lipidosis caused by mutations in the NPC1 gene or, in a few patients, the HE1 gene, which encode sterol regulating proteins. NPC is characterised by a complex lipid anomaly including a disturbed cellular trafficking of cholesterol but also multi-lipid storage in visceral organs and brain. Lipids were studied using conventional methods in enlarged spleens that had been removed from five patients for different therapeutic and diagnostic reasons and found to have microscopic signs of lysosomal storage disease not suspected clinically. The spleen lipid findings with a concurrent accumulation of cholesterol, sphingomyelin and glucosylceramide (Acc-CSG) allowed us to suggest NPC diagnoses for these patients, who were free of neurologic symptoms. From two patients no material for confirmatory studies was available, but in two other patients NPC diagnoses could be confirmed with the filipin cytochemical cholesterol assay and NPC1 gene analysis, respectively. However, these tests and also HE1 gene analysis were negative in a third patient. Since the Acc-CSG lipid pattern seems to indicate a multi-lipid trafficking defect rather than being highly specific for NPC, this patient, if not affected with very atypical NPC, may be a candidate for a different lipid trafficking disorder. The Acc-CSG pattern was considered to be similar to the lipid pattern known for the lipid rafts, these functional cell structures being probably disorganised and accumulated in late endosomes and lysosomes of NPC cells.

Adult↗