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  • Solubilization of low-density lipoprotein with sodium deoxycholate and recombination of apoprotein B with dimyristoylphosphatidylcholine. 6882744

    Apoprotein B (apoB) of human plasma low-density lipoprotein (LDL) (d 1.025-1.050 g/mL) has been solubilized with solid sodium deoxycholate (NaDC) above its critical micellar concentration. ApoB is isolated by gel-filtration chromatography as a mixed micellar complex of protein and detergent in high yield in a lipid-free form. A soluble apoB-dimyristoylphosphatidylcholine (DMPC) complex has been prepared by incubation of aqueous solutions of apoB-NaDC and DMPC-NaDC (2/1 w/w) at room temperature with detergent removal by extensive dialysis. A combination of gel chromatographic and density gradient fractionation of DMPC-apoB incubation mixtures demonstrates that a reasonably well-defined complex of DMPC and apoB is formed with a 4:1 w/w lipid:protein ratio. Negative-stain electron microscopy shows these particles to be single-bilayer phospholipid vesicles with a diameter of 210 +/- 20 A into which the apoB is incorporated. Circular dichroic spectra of NaDC-solubilized apoB show apoB to have similar conformation to that seen in the native LDL particle. However, apoB that has been complexed with DMPC exhibits more alpha-helix. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis shows a single band (apparent Mr 366000) for apoB after solubilization, purification, and interaction with phospholipid. The behavior of apoB during its reassociation with phospholipid and the structural features of the DMPC-apoB particle are similar to those observed in the interaction of solubilized membrane proteins with lipid rather than that of other apo-lipoproteins.
    Document Type:
    Reference
    Product Catalog Number:
    ALP20
    Product Catalog Name:
    Apolipoprotein A-II, human

  • Cellular and synaptic mechanisms of anti-NMDA receptor encephalitis. 20427647

    We recently described a severe, potentially lethal, but treatment-responsive encephalitis that associates with autoantibodies to the NMDA receptor (NMDAR) and results in behavioral symptoms similar to those obtained with models of genetic or pharmacologic attenuation of NMDAR function. Here, we demonstrate that patients' NMDAR antibodies cause a selective and reversible decrease in NMDAR surface density and synaptic localization that correlates with patients' antibody titers. The mechanism of this decrease is selective antibody-mediated capping and internalization of surface NMDARs, as Fab fragments prepared from patients' antibodies did not decrease surface receptor density, but subsequent cross-linking with anti-Fab antibodies recapitulated the decrease caused by intact patient NMDAR antibodies. Moreover, whole-cell patch-clamp recordings of miniature EPSCs in cultured rat hippocampal neurons showed that patients' antibodies specifically decreased synaptic NMDAR-mediated currents, without affecting AMPA receptor-mediated currents. In contrast to these profound effects on NMDARs, patients' antibodies did not alter the localization or expression of other glutamate receptors or synaptic proteins, number of synapses, dendritic spines, dendritic complexity, or cell survival. In addition, NMDAR density was dramatically reduced in the hippocampus of female Lewis rats infused with patients' antibodies, similar to the decrease observed in the hippocampus of autopsied patients. These studies establish the cellular mechanisms through which antibodies of patients with anti-NMDAR encephalitis cause a specific, titer-dependent, and reversible loss of NMDARs. The loss of this subtype of glutamate receptors eliminates NMDAR-mediated synaptic function, resulting in the learning, memory, and other behavioral deficits observed in patients with anti-NMDAR encephalitis.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Hypoxia induced upregulation and function of the thiamine transporter, SLC19A3 in a breast cancer cell line. 20930543

    Adaptive responses within hypoxic tumor microenvironments require the altered expression of Solute Carrier (SLC) transporters to maintain nutrient uptake in support of cellular metabolism and biosynthesis. Using a real time PCR array strategy to further characterize changes in transporter expression within a chronic hypoxia breast cancer cell line model (BT474), we have found a 31 fold increase in the expression of the thiamine transporter, SLC19A3. Thus, further investigations into the expression changes of the thiamine transporters, SLC19A2 and SLC19A3, and the role of hypoxia inducible factor-1 alpha (HIF-1α) regulating their expression were conducted. Chronic culturing of BT474 cells in 1% O2 up to 142 days consistently demonstrated a high level of SLC19A3 expression with a mean of approximately 40 fold with no change in SLC19A2. A corresponding 2 fold increase in thiamine uptake over 15 min was measured in chronic hypoxic BT474 cells compared to normoxia. Acute 1% O2 exposure of BT474 cells up to 72 h demonstrated a 7.5 fold increase in SLC19A3 expression. The chemical hypoxia mimetic deferoxamine, resulted in an approximately 70 fold increase in SLC19A3 expression. Stable shRNA knockdown of HIF-1α reduced hypoxia mediated SLC19A3 up-regulation by approximately 3 fold compared to scrambled construct. In conclusion, SLC19A3 transporter expression was observed to be up-regulated under acute, chronic and DFO induced hypoxia. The attenuated increase in SLC19A3 expression after HIF-1α knockdown suggests a role for HIF-1α mediated pathways regulating SLC19A3 gene expression.
    Document Type:
    Reference
    Product Catalog Number:
    ABC41
    Product Catalog Name:
    Anti-Mitofusin-1 Antibody