16 research outputs found
C. elegans Agrin Is Expressed in Pharynx, IL1 Neurons and Distal Tip Cells and Does Not Genetically Interact with Genes Involved in Synaptogenesis or Muscle Function
Agrin is a basement membrane protein crucial for development and maintenance of the neuromuscular junction in vertebrates. The C. elegans genome harbors a putative agrin gene agr-1. We have cloned the corresponding cDNA to determine the primary structure of the protein and expressed its recombinant fragments to raise specific antibodies. The domain organization of AGR-1 is very similar to the vertebrate orthologues. C. elegans agrin contains a signal sequence for secretion, seven follistatin domains, three EGF-like repeats and two laminin G domains. AGR-1 loss of function mutants did not exhibit any overt phenotypes and did not acquire resistance to the acetylcholine receptor agonist levamisole. Furthermore, crossing them with various mutants for components of the dystrophin-glycoprotein complex with impaired muscle function did not lead to an aggravation of the phenotypes. Promoter-GFP translational fusion as well as immunostaining of worms revealed expression of agrin in buccal epithelium and the protein deposition in the basal lamina of the pharynx. Furthermore, dorsal and ventral IL1 head neurons and distal tip cells of the gonad arms are sources of agrin production, but no expression was detectable in body muscles or in the motoneurons innervating them. Recombinant worm AGR-1 fragment is able to cluster vertebrate dystroglycan in cultured cells, implying a conservation of this interaction, but since neither of these proteins is expressed in muscle of C. elegans, this interaction may be required in different tissues. The connections between muscle cells and the basement membrane, as well as neuromuscular junctions, are structurally distinct between vertebrates and nematodes
Oxidation of hemoglobin and redistribution of band 3 promote erythrophagocytosis in visceral leishmaniasis
In visceral leishmaniasis (VL), oxidative
assault on erythrocytes perturbs their cellular environment
and makes them vulnerable to premature hemolysis. In this
study, we assessed the contribution of oxidation-induced
modifications of hemoglobin and membrane protein band 3
in the reduced survival of red cells in VL. Oxidative
transformation of oxyhemoglobin to hemichrome enhanced
its interaction with erythrocyte membrane in the infected
animals. Association between denatured globin and band 3
contributed to the formation of insoluble copolymer of
macromolecular dimension. Disulfide bonding appeared to
be necessary in the making of high molecular weight
aggregates during copolymerization. Hemichrome induced
clustering of band 3 promoted generation of epitopes on
erythrocyte cell surface. This provided a signal favoring
immunologic recognition of redistributed band 3 by
autologous IgG followed by erythrophagocytosis. An
eventual outcome of the sequence of events pointed to
early removal of affected red cells from circulation during
the disease