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  • 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.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • 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.
    Tipo de documento:
    Referencia
    Referencia del producto:
    ALP20
    Nombre del producto:
    Apolipoprotein A-II, human

  • 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.
    Tipo de documento:
    Referencia
    Referencia del producto:
    ABC41
    Nombre del producto:
    Anti-Mitofusin-1 Antibody

  • Mutagenesis and analysis of genetic mutations in the GC-rich KISS1 receptor sequence identified in humans with reproductive disorders. 21912371

    The kisspeptin receptor (KISS1R) is a G protein-coupled receptor recognized as the trigger of puberty and a regulator of reproductive competence in adulthood (1,2,3). Inactivating mutations in KISS1R identified in patients have been associated with iodiopathic hypogonadotropic hypogonadism (IHH) (1,2) and precocious puberty (4). Functional studies of these mutants are crucial for our understanding of the mechanisms underlying the regulation of reproduction by this receptor as well as those shaping the disease outcomes, which result from abnormal KISS1R signaling and function. However, the highly GC-rich sequence of the KISS1R gene makes it rather difficult to introduce mutations or amplify the gene encoding this receptor by PCR. Here we describe a method to introduce mutations of interest into this highly GC-rich sequence that has been used successfully to generate over a dozen KISS1R mutants in our laboratory. We have optimized the PCR conditions to facilitate the amplification of a range of KISS1R mutants that include substitutions, deletions or insertions in the KISS1R sequence. The addition of a PCR enhancer solution, as well as of a small percentage of DMSO were especially helpful to improve amplification. This optimized procedure may be useful for other GC-rich templates as well. The expression vector encoding the KISS1R is been used to characterize signaling and function of this receptor in order to understand how mutations may change KISS1R function and lead to the associated reproductive phenotypes. Accordingly, potential applications of KISS1R mutants generated by site-directed mutagenesis can be illustrated by many studies (1,4,5,6,7,8). As an example, the gain-of-function mutation in the KISS1R (Arg386Pro), which is associated with precocious puberty, has been shown to prolong responsiveness of the receptor to ligand stimulation (4) as well as to alter the rate of degradation of KISS1R (9). Interestingly, our studies indicate that KISS1R is degraded by the proteasome, as opposed to the classic lysosomal degradation described for most G protein-coupled receptors (9). In the example presented here, degradation of the KISS1R is investigated in Human Embryonic Kidney Cells (HEK-293) transiently expressing Myc-tagged KISS1R (MycKISS1R) and treated with proteasome or lysosome inhibitors. Cell lysates are immunoprecipitated using an agarose-conjugated anti-myc antibody followed by western blot analysis. Detection and quantification of MycKISS1R on blots is performed using the LI-COR Odyssey Infrared System. This approach may be useful in the study of the degradation of other proteins of interest as well.
    Tipo de documento:
    Referencia
    Referencia del producto:
    16-219
    Nombre del producto:
    Anti-Myc Tag Antibody, clone 4A6, agarose conjugate

  • Cdk5 regulates the phosphorylation of tyrosine 1472 NR2B and the surface expression of NMDA receptors. 18184784

    NMDA receptors (NMDARs) are a major class of ionotropic glutamate receptors that can undergo activity-dependent changes in surface expression. Clathrin-mediated endocytosis is a mechanism by which the surface expression of NR2B-containing NMDA receptors is regulated. The C terminus of the NMDA receptor subunit NR2B contains the internalization motif YEKL, which is the binding site for the clathrin adaptor AP-2. The tyrosine (Y1472) within the YEKL motif is phosphorylated by the Src family of kinases and this phosphorylation inhibits the binding of AP-2 and promotes surface expression of NMDA receptors. Cdk5 is a serine/threonine kinase that has been implicated in synaptic plasticity, learning, and memory. Here we demonstrate that inhibition of Cdk5 results in increased phosphorylation of Y1472 NR2B at synapses and decreased binding of NR2B to beta2-adaptin, a subunit of AP-2, thus blocking the activity-dependent endocytosis of NMDA receptors. Furthermore, we show that inhibition of Cdk5 increases the binding of Src to postsynaptic density-95 (PSD-95), and that expression of PSD-95 facilitates the phosphorylation of Y1472 NR2B by Src. Together, these results suggest a model in which inhibition of Cdk5 increases the binding of Src to PSD-95 and the phosphorylation of Y1472 NR2B by Src, which results in decreased binding of NR2B to AP-2, and NR2B/NMDAR endocytosis. This study provides a novel molecular mechanism for the regulation of the surface expression of NR2B-containing NMDA receptors and gives insight into the Cdk5-dependent regulation of synaptic plasticity.
    Tipo de documento:
    Referencia
    Referencia del producto:
    LP1
    Nombre del producto:
    VLDL, human