Showing papers by "Deepak Sharma published in 2004"
TL;DR: It is demonstrated that a brief treatment of cultured cells with natural or synthetic glycosphingolipids (GSLs) or elevation of cholesterol (either by acute treatment with mbeta-cyclodextrin/cholesterol or by alteration of growth conditions) dramatically stimulates caveolar endocytosis with little or no effect on other endocytic mechanisms.
Abstract: Internalization of some plasma membrane constituents, bacterial toxins, and viruses occurs via caveolae; however, the factors that regulate caveolar internalization are still unclear. Here, we demonstrate that a brief treatment of cultured cells with natural or synthetic glycosphingolipids (GSLs) or elevation of cholesterol (either by acute treatment with mbeta-cyclodextrin/cholesterol or by alteration of growth conditions) dramatically stimulates caveolar endocytosis with little or no effect on other endocytic mechanisms. These treatments also stimulated the movement of GFP-labeled vesicles in cells transfected with caveolin-1-GFP and reduced the number of surface-connected caveolae seen by electron microscopy. In contrast, overexpression of caveolin-1 decreased caveolar uptake, but treatment with GSLs reversed this effect and stimulated caveolar endocytosis. Stimulation of caveolar endocytosis did not occur using ceramide or phosphatidylcholine and was not due to GSL degradation because similar results were obtained using a nonhydrolyzable GSL analog. Stimulated caveolar endocytosis required src kinase and PKC-alpha activity as shown by i) use of pharmacological inhibitors, ii) expression of kinase inactive src or dominant negative PKCalpha, and iii) stimulation of src kinase activity upon addition of GSLs or cholesterol. These results suggest that caveolar endocytosis is regulated by a balance of caveolin-1, cholesterol, and GSLs at the plasma membrane.
274 citations
TL;DR: Results suggest that the core of PHF6 is localized at VYK, and the interaction between small amphiphilic segments of tau may initiate nucleation and lead to filaments displaying paired helical filament morphology.
200 citations
TL;DR: The data suggest that abnormal membrane recycling in NPFs results from specific inhibition of rab4 function by excess cholesterol in EEs, which is similar to that seen in normal HSFs.
Abstract: 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°C to label early endosomes (EEs), shifted to 37°C, and lipid recycling was quantified. Using dominant negative rabs, we showed that, in normal HSFs, LacCer recycling was rapid (t1/2 8 min) and mainly rab4-dependent. In NPFs, LacCer recycling was delayed (t1/2 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.
151 citations
TL;DR: The consortium was able to efficiently decolorize various TPM dyes viz.
Abstract: Various soil and sludge samples collected from the vicinity of textile dyeing industries and waste disposal sites were used for enrichment of microbial population in the presence of triphenylmethane (TPM) dye Acid Violet-17 (AV-17). Twenty-five (25) isolates were screened for their ability to decolorize AV-17 dye added at a rate of 10 mgl(-1) in mineral salts medium (MSM) agar plates. Five bacterial isolates belonging to Bacillus sp., Alcaligenes sp. and Aeromonas sp. were selected on the basis of their higher decolorization ability and were used to develop a bacterial consortium. The consortium was able to efficiently decolorize various TPM dyes viz. Acid Violet-17 (86%), Acid Blue-15 (85%), Crystal Violet (82%), Malachite Green (82%) and Brilliant Green (85%). The consortium will be further used for designing efficient and cost effective treatment system for effluents of textile processing industries (TPI).
67 citations
TL;DR: An up-flow immobilized cell bioreactor was developed using a microbial consortium, consisting of Bacillus sp.
Abstract: An up-flow immobilized cell bioreactor was developed using a microbial consortium, consisting of Bacillus sp., Alcaligenes sp. and Aeromonas sp., immobilized on refractory brick pieces as immobilization support. malachite green, a model triphenylmethane dye was decolourized by more than 93% within 48 h (operating conditions: initial dye concentration 30 mg l−1; flow rate 6 ml h−1). The analytical studies based on TLC and 1H NMR showed degradation of the aromatic rings of the malachite green into simpler metabolic intermediates.
16 citations