The role of glyceraldehyde 3-phosphate dehydrogenase (GapA-1) in <Emphasis Type="Italic">Neisseria meningitidis</Emphasis> adherence to human cells

Background  

Glyceraldehyde 3-phosphate dehydrogenases (GAPDHs) are cytoplasmic glycolytic enzymes, which although lacking identifiable secretion signals, have also been found localized to the surface of several bacteria (and some eukaryotic organisms); where in some cases they have been shown to contribute to the colonization and invasion of host tissues. Neisseria meningitidis is an obligate human nasopharyngeal commensal which can cause life-threatening infections including septicaemia and meningitis. N. meningitidis has two genes, gapA-1 and gapA-2, encoding GAPDH enzymes. GapA-1 has previously been shown to be up-regulated on bacterial contact with host epithelial cells and is accessible to antibodies on the surface of capsule-permeabilized meningococcal cells. The aims of this study were: 1) to determine whether GapA-1 was expressed across different strains of N. meningitidis; 2) to determine whether GapA-1 surface accessibility to antibodies was dependant on the presence of capsule; 3) to determine whether GapA-1 can influence the interaction of meningococci and host cells, particularly in the key stages of adhesion and invasion.     

Inhibition of Calcineurin-mediated Endocytosis and ��-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid (AMPA) Receptors Prevents Amyloid �� Oligomer-induced Synaptic Disruption

Synaptic degeneration, including impairment of synaptic plasticity and loss of synapses, is an important feature of Alzheimer disease pathogenesis. Increasing evidence suggests that these degenerative synaptic changes are associated with an accumulation of soluble oligomeric assemblies of amyloid β (Aβ) known as ADDLs. In primary hippocampal cultures ADDLs bind to a subpopulation of neurons. However the molecular basis of this cell type-selective interaction is not understood. Here, using siRNA screening technology, we identified α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits and calcineurin as candidate genes potentially involved in ADDL-neuron interactions. Immunocolocalization experiments confirmed that ADDL binding occurs in dendritic spines that express surface AMPA receptors, particularly the calcium-impermeable type II AMPA receptor subunit (GluR2). Pharmacological removal of the surface AMPA receptors or inhibition of AMPA receptors with antagonists reduces ADDL binding. Furthermore, using co-immunoprecipitation and photoreactive amino acid cross-linking, we found that ADDLs interact preferentially with GluR2-containing complexes. We demonstrate that calcineurin mediates an endocytotic process that is responsible for the rapid internalization of bound ADDLs along with surface AMPA receptor subunits, which then both colocalize with cpg2, a molecule localized specifically at the postsynaptic endocytic zone of excitatory synapses that plays an important role in activity-dependent glutamate receptor endocytosis. Both AMPA receptor and calcineurin inhibitors prevent oligomer-induced surface AMPAR and spine loss. These results support a model of disease pathogenesis in which Aβ oligomers interact selectively with neurotransmission pathways at excitatory synapses, resulting in synaptic loss via facilitated endocytosis. Validation of this model in human disease would identify therapeutic targets for Alzheimer disease.     

The complete mitochondrial DNA sequence of the shark Mustelus manazo: evaluating rooting contradictions to living bony vertebrates

A remarkable example of a misleading mitochondrial protein tree is presented, involving ray-finned fishes, coelacanths, lungfishes, and tetrapods, with sea lampreys as an outgroup. In previous molecular phylogenetic studies on the origin of tetrapods, ray-finned fishes have been assumed as an outgroup to the tetrapod/lungfish/coelacanth clade, an assumption supported by morphological evidence. Standard methods of molecular phylogenetics applied to the protein-encoding genes of mitochondria, however, give a bizarre tree in which lamprey groups with lungfish and, therefore, ray-finned fishes are not the outgroup to a tetrapod/lungfish/coelacanth clade. All of the dozens of published phylogenetic methods, including every possible modification to maximum likelihood known to us (such as inclusion of site heterogeneity and exclusion of potentially misleading hydrophobic amino acids), fail to place the ray-finned fishes in a biologically acceptable position. A likely cause of this failure may be the use of an inappropriate outgroup. Accordingly, we have determined the complete mitochondrial DNA sequence from the shark, Mustelus manazo, which we have used as an alternative and more proximal outgroup than the lamprey. Using sharks as the outgroup, lungfish appear to be the closest living relative of tetrapods, although the possibility of a lungfish/coelacanth clade being the sister group of tetrapods cannot be excluded.      

Distribution of progestin-binding cells in estrogen-treated and untreated neonatal mouse uterus and oviduct: autoradiographic study with [125I]progestin

Progestin-binding sites in uteri and oviducts of estrogen-treated and untreated 8-day-old mice were studied by thaw-mount autoradiography with [125I]progestin. In the untreated uteri, nuclear concentration of radiolabelled progestin was observed in all tissues of the uterus, with strongest nuclear labelling in luminal and glandular epithelia and in stroma. In the estrogen-treated uteri, the degree of labelling was markedly augmented in stroma and muscle, but much reduced in the luminal and glandular epithelia, compared to untreated uteri. In untreated oviducts, nuclear labelling was observed in stroma and muscle in all regions and in epithelium in the isthmic and uterine regions. The epithelium in infundibular and ampullar regions was only scarcely labelled. The estrogen-treatment augmented the labelling in stroma and muscle of the oviduct as in the uterus, but the labelling in epithelium was not affected. These results indicate that estrogen-treatment induces progesterone receptor differentially among tissue compartments both in the uterus and oviduct.