Disease relevance of Filipin

• In addition to its effects in CaCo-2 cells that express low levels of caveolin, filipin also inhibited CT activity in human epidermoid carcinoma A431 and Jurkat T lymphoma cells that are, respectively, rich in or lack caveolin [1].
• Fluorescence microscopic examination of filipin-stained cultured skin fibroblasts derived from two brothers with group D Niemann-Pick disease revealed abnormal storage of low density lipoprotein (LDL)-derived cholesterol [2].
• The staining patterns of BCtheta and filipin in human epidermoid carcinoma A431 cells with and without cholesterol depletion suggest that BCtheta binds to specific membrane domains on the cell surface, whereas filipin binding is indiscriminate to cell cholesterol [3].
• By using the probe 4-amino-5-methylamino-2',7'-difluorofluorescein, it was found that the NO level in the glioma population was increased by 15% after 1 or 10 cytoplasmic traversals, and this NO production was inhibited by filipin [4].
• Mycoplasma gallisepticum was adapted to grow with delta 5-sterols modified in the aliphatic side chain, and stopped-flow kinetic measurements of filipin association were made to estimate the sterol distribution between the two leaflets of the membrane [5].

High impact information on Filipin

• Filipin binding to other membranes was unchanged [6].
• Using another cholesterol probe, the saponin tomatin, applied alone and after filipin treatment, we now present evidence that both the band and inter-band domains of the smooth muscle plasma membrane are cholesterol-rich [7].
• Failure of filipin to detect cholesterol-rich domains in smooth muscle plasma membrane [7].
• Opposite polarity of filipin-induced deformations in the membrane of condensing vacuoles and zymogen granules [8].
• M-cell apical plasma membranes were rich in cholesterol, displaying numerous filipin-induced membrane lesions in thin sections and freeze-fracture replicas [9].

Chemical compound and disease context of Filipin

• We also found that rotaviruses infected cells in which caveolar uptake was blocked; treatment with the cholesterol binding agents nystatin and filipin, as well as transfection of cells with dominant-negative caveolin-1 and caveolin-3 mutants, had no effect on rotavirus infection [10].
• To determine whether lipid rafts are needed for BoNT/A activity, those associated with the plasma membranes of murine N2a neuroblastoma cells were disrupted using either methyl-beta-cyclodextrin or filipin [11].
• In a sucrose medium, filipin-induced hemolysis is inhibited in humans, whereas it is stimulated in pig erythrocytes [12].
• However, the highest reduction of the electrophoretic mobility and protection from filipin-induced hemolysis of pretreated RBC was found with ZIMET 3164 [13].

Biological context of Filipin

• Interestingly, filipin appears to inhibit insulin uptake by endothelium for transcytosis, a caveolae-mediated process, but not endocytosis for degradation, apparently mediated by the clathrin-coated pathway [14].
• Rat lung microvascular permeability to albumin in situ is significantly decreased after filipin perfusion [14].
• Protease treatment mimicked capacitation by increasing the acrosome-reaction incidence as well as PXB binding, at enzyme concentrations not affecting the surface coat nor altering filipin/sterol localization [15].
• This cellular phenotype is identifiable cytologically by filipin staining and biochemically by measurement of low-density lipoprotein-derived cholesterol esterification [16].
• Cells were irradiated in the presence of Filipin, an agent that disrupts lipid rafts, effectively inhibiting membrane signaling, and the induction of sister chromatid exchange and HPRT mutations by very low fluences of alpha particles (mean doses 0.17-0.5 cGy) was measured [17].

Anatomical context of Filipin

• We also determined the distribution of morphologically detectable cholesterol in M-cell plasma and intracellular membranes in dome epithelium exposed to the polyene antibiotic, filipin [9].
• In contrast, apical membrane endocytic pits and coated vesicles in M cells failed to show filipin-induced membrane lesions [9].
• Uptake of caveolae and degradation of PrPC was slow and sensitive to filipin [18].
• This permitted us to identify all of the vesicles involved in the transport of LDL to the lysosome and to determine whether the membranes of these vesicles were able to bind filipin [19].
• Filipin significantly reduces the transcellular transport of insulin and albumin across cultured endothelial cell monolayers [14].

Associations of Filipin with other chemical compounds

• This destruction was preceded by an increase in the cholesterol content of crystalloid ER membranes, as judged by a 4- to 8-fold increase in their ability to form complexes with filipin, a cholesterol-binding compound that can be visualized in freeze-fracture electron micrographs [6].
• When isolated Golgi apparatus is fixed with glutaraldehyde to maintain the three-dimensional orientation of cisternae and secretory vesicles, and then treated with filipin, cisternal membranes on both cis and trans faces of the apparatus as well as secretory granule membranes appear to be affected about equally [20].
• However, CT activation as determined by its reduction to form the A1 peptide and CT activity as measured by cyclic AMP accumulation were inhibited in filipin-treated cells [1].
• In addition, Filipin, which forms complexes with cellular cholesterol, labeled the Golgi apparatus of fixed cells and inhibited accumulation of C6-NBD-Cer at the Golgi apparatus [21].
• The role of lipid rafts in GLUT4 trafficking was studied by adding nystatin or filipin at concentrations that specifically disrupt caveolae morphology and inhibit caveolae function without altering clathrin-mediated endocytosis [22].

Gene context of Filipin

• Nystatin and filipin also affected the rate of internalization of CCR5, indicating a role for caveolae [23].
• LXR agonist treatment prior to and during apoA-I incubation resulted in reduction in filipin staining of unesterified cholesterol in late endosomes/lysosomes, as well as cholesterol mass, in NPC1(-/-) cells [24].
• We show here that modifying lipid rafts either by cholesterol depletion using methyl-beta-cyclodextrin and filipin or by conversion of sphingomyelin to ceramide with exogenous bacterial sphingomyelinase (bSMase) markedly activated the PLD of human PBMC. bSMase was the most potent PLD activator, giving maximal 6- to 7-fold increase in PLD activity [25].
• In the Jurkat T lymphocyte cell line, which does not express caveolin-1, nuclear translocation of IFNGR-1 and STAT1alpha were similarly inhibited by filipin pretreatment [26].
• Disruption of lipid rafts/caveolae by depleting cellular cholesterol with cholesterol-binding reagent, beta-methylcyclodextrin or filipin, blocks the IGF-1 receptor signaling in 3T3-L1 preadipocyte [27].

Analytical, diagnostic and therapeutic context of Filipin

• This level of filipin does not solubilize the enzymes but causes both puckering of Golgi membranes visible by electron microscopy and disruption of the Golgi vesicles as measured by release of serum albumin [20].
• Indirect immunofluorescence with a monoclonal antibody specific for a lysosomal/endosomal fraction revealed a staining pattern that colocalized with the filipin signal [28].
• In immunocytochemistry, GPI-ACE showed patchy, uneven distribution on the plasma membrane that was restored by filipin [29].
• The beta(2)AR-stimulated increase in the myocyte contraction rate is increased by approximately 2-fold and markedly prolonged by filipin, an agent that disrupts lipid rafts such as caveolae and significantly reduces co-immunoprecipitation of beta(2)AR and caveolin 3 and co-migration of beta(2)AR and caveolin-3 enriched membranes [30].
• The crystalloid ER membranes are low in cholesterol, as indicated by the small number of filipin-cholesterol complexes in freeze-fracture images after treatment with filipin [31].

References