Isolation and characterization of heparan sulfate from various murine tissues

Heparan sulfate (HS), is a proteoglycan (PG) found both in the extracellular matrix and on cell surface. It may represent one of the most biologically important glycoconjugates, playing an essential role in a variety of different events at molecular level. The publication of the mouse genome, and the intensive investigations aimed at understanding the proteome it encodes, has motivated us to initiate studies in mouse glycomics focused on HS. The current study is aimed at determining the quantitative and qualitative organ distribution of HS in mice. HS from brain, eyes, heart, lung, liver, kidney, spleen, intestine and skin was purified from 6–8 week old male and female mice. The recovered yield of HS from these organs is compared with the recovered whole body yield of HS. Structural characterization of the resulting HS relied on disaccharide analysis and ¹H-NMR spectroscopy. Different organs revealed a characteristic HS structure. These data begin to provide a structural understanding of the role of HS in cell-cell interactions, cell signaling and sub-cellular protein trafficking as well as a fundamental understanding of certain aspects of protein-carbohydrate interactions.     

Methamphetamine-induced spectrin proteolysis in the rat striatum

Methamphetamine (METH) is a widely abused psychostimulant. Multiple high doses of METH cause long-term toxicity to dopamine (DA) and serotonin (5-HT) nerve terminals in the brain, as evidenced by decreases in DA and 5-HT content, decreases in tyrosine and tryptophan hydroxylase activities, decreases in DA and 5-HT re-uptake sites, and nerve terminal degeneration. Multiple high doses of METH are known to elicit a rapid increase in DA release and hyperthermia. Although METH also produces a delayed and sustained rise in glutamate, no studies have shown whether METH produces structural evidence of excitotoxicity in striatum, or identified the receptors that mediate this toxicity directly, independent of alterations in METH-induced hyperthermia. These experiments investigated whether METH can cause excitotoxicity as evidenced by cytoskeletal protein breakdown in a glutamate receptor-dependent manner. METH increased calpain-mediated spectrin proteolysis in the rat striatum 5 and 7 days after METH administration without affecting caspase 3-dependent spectrin breakdown. This effect was completely blocked with the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist, GYKI 52466, but not the NMDA receptor antagonist, MK-801. However, AMPA or NMDA receptor antagonism did not attenuate the METH-induced depletions of the dopamine transporter (DAT). Independent mechanisms involved in mediating spectrin proteolysis and DAT protein loss are discussed.     

Mitochondrial targeting of recombinant RNAs modulates the level of a heteroplasmic mutation in human mitochondrial DNA associated with Kearns Sayre Syndrome

Mitochondrial mutations, an important cause of incurable human neuromuscular diseases, are mostly heteroplasmic: mutated mitochondrial DNA is present in cells simultaneously with wild-type genomes, the pathogenic threshold being generally >70% of mutant mtDNA. We studied whether heteroplasmy level could be decreased by specifically designed oligoribonucleotides, targeted into mitochondria by the pathway delivering RNA molecules in vivo. Using mitochondrially imported RNAs as vectors, we demonstrated that oligoribonucleotides complementary to mutant mtDNA region can specifically reduce the proportion of mtDNA bearing a large deletion associated with the Kearns Sayre Syndrome in cultured transmitochondrial cybrid cells. These findings may be relevant to developing of a new tool for therapy of mtDNA associated diseases.     

Nicotinic acetylcholine receptors: A comparison of the nAChRs of Caenorhabditis elegans and parasitic nematodes

Nicotinic acetylcholine receptors (nAChRs) play a key role in the normal physiology of nematodes and provide an established target site for anthelmintics. The free-living nematode, Caenorhabditis elegans, has a large number of nAChR subunit genes in its genome and so provides an experimental model for testing novel anthelmintics which act at these sites. However, many parasitic nematodes lack specific genes present in C. elegans, and so care is required in extrapolating from studies using C. elegans to the situation in other nematodes. In this review the properties of C. elegans nAChRs are reviewed and compared to those of parasitic nematodes. This forms the basis for a discussion of the possible subunit composition of nAChRs from different species of parasitic nematodes. Currently our knowledge on this is largely based on studies using heterologous expression and pharmacological analysis of receptor subunits in Xenopus laevis oocytes. It is concluded that more information is required regarding the subunit composition and pharmacology of endogenous nAChRs in parasitic nematodes.     

Evidence for the Circulation and Inter-Hemispheric Movement of the H14 Subtype Influenza A Virus

Three H14 influenza A virus (IAV) isolates recovered in 2010 during routine virus surveillance along the Mississippi Migratory Bird Flyway in Wisconsin, U.S.A. raised questions about the natural history of these rare viruses. These were the first H14 IAV isolates recovered in the Western Hemisphere and the only H14 IAV isolates recovered since the original four isolates in 1982 in Asia. Full length genomic sequencing of the 2010 H14 isolates demonstrated the hemagglutinin (HA) gene from the 1982 and 2010 H14 isolates showed 89.6% nucleotide and 95.6% amino acid similarity and phylogenetic analysis of these viruses placed them with strong support within the H14 subtype lineage. The level of genomic divergence observed between the 1982 and 2010 viruses provides evidence that the H14 HA segment was circulating undetected in hosts and was not maintained in environmental stasis. Further, the evolutionary relationship observed between 1982 H14 and the closely related H4 subtype HA segments were similar to contemporary comparisons suggesting limited adaptive divergence between these sister subtypes. The nonstructural (NS) segment of one 2010 isolate was placed in a NS clade isolated infrequently over the last several decades that includes the NS segment from a previously reported 1982 H14 isolate indicating the existence of an unidentified pool of genomic diversity. An additional neuraminidase reassortment event indicated a recent inter-hemispheric gene flow from Asia into the center of North America. These results demonstrate temporal and spatial gaps in the understanding of IAV natural history. Additionally, the reassortment history of these viruses raises concern for the inter-continental spread of IAVs and the efficacy of current IAV surveillance efforts in detecting genomic diversity of viruses circulating in wild birds.     

Epithelial trafficking of Sonic hedgehog by megalin.

We present here evidence of in vivo epithelial endocytosis and trafficking of non-lipid-modified Sonic hedgehog (ShhN) when infused into rat efferent ducts via microinjection. Initially, exogenous ShhN is detected in endocytic vesicles and early endosomes located near the apical plasma membrane of non-ciliated cells. Within 30-60 min following infusion, ShhN can be detected in lysosomes and at basolateral regions of non-ciliated cells. Basolaterally, ShhN was observed along the extracellular surfaces of interdigitated plasma membranes of adjacent cells and in the extracellular compartment underlying the efferent duct epithelium. Uptake and subcellular trafficking of infused ShhN by non-ciliated cells could be blocked by either anti-megalin IgG or the megalin antagonist, RAP. Ciliated cells, which do not express megalin, displayed little if any apical internalization of ShhN even though they were found to express Patched-1. However, ShhN was found in coated pits of lateral plasma membranes of ciliated cells as well as in underlying endocytic vesicles. We conclude that megalin-mediated endocytosis of ShhN can occur in megalin-expressing epithelia in vivo, and that the internalized ShhN can be targeted to the lysosome or transcytosed in the plane of the epithelium or across the epithelium. These findings highlight the multiple mechanisms by which megalin may influence Shh morphogen gradients in vivo.     

Ganglioside GD3 and GD3-lactone mediated regulation of the intermolecular organization in mixed monolayers with dipalmitoylphosphatidylcholine

The interactions of dpPC with ganglioside GD3 and two lactones, GD3LacI or GD3LacII, in lipid monolayers occur with reduced, unaltered, or increased molecular area and surface potential/molecule, respectively. dpPC is fully miscible with GD3 and GD3LacI but films with GD3LacII show immiscibility above 75 mol% lactone. At low proportions of GD3 in mixtures with dpPC, GD3 undergoes condensation and depolarization; dpPC is depolarized and its molecular area is reduced above 50 mol% GD3. GD3LacI forms ideally mixed films with dpPC. Mixtures of dpPC with GD3LacII at mole fractions below 0.3 show increased mean molecular area and surface potential/molecule mostly due to lactone alterations. Between mole fractions of 0.3 and 0.75 the surface parameters of dpPC are altered, and above these proportions both lipids are immiscible. Defined variations of molecular properties induced by ganglioside lactonization are selectively transduced to changes of the intermolecular organization and surface electrostatics in mixed interfaces with dpPC. Thus, changes in the relative proportions of a ganglioside and its lactone forms may act as sensitive biotransducers for membrane-mediated cellular functions, without the need for metabolically altering the concentration of gangliosides.     

Screening method for cDNAs encoding putative enzymes converting loganin into secologanin by a transgenic yeast culture

A screening method was developed for the detection of enzymes converting loganin to secologanin, a precursor in the biosynthesis of indole alkaloids. The method uses a transgenic yeast culture expressing two cDNAs encoding enzymes involved in the terpenoid indole alkaloid biosynthesis. In the presence of secologanin, the yeast culture produces a yellow compound visible on nitrocellulose. This color change was used to screen a cDNA library of Catharanthus roseus for a putative enzyme converting loganin into secologanin.