title: CK2 phosphorylation of Schistosoma mansoni HMGB1 protein regulates its cellular traffic and secretion but not its DNA transactions.
abstract: BACKGROUND
  The helminth Schistosoma mansoni parasite resides in mesenteric veins where fecundated female worms lay hundred of eggs daily. Some of the egg antigens are trapped in the liver and induce a vigorous granulomatous response. High Mobility Group Box 1 (HMGB1), a nuclear factor, can also be secreted and act as a cytokine. Schistosome HMGB1 (SmHMGB1) is secreted by the eggs and stimulate the production of key cytokines involved in the pathology of schistosomiasis. Thus, understanding the mechanism of SmHMGB1 release becomes mandatory. Here, we addressed the question of how the nuclear SmHMGB1 can reach the extracellular space.
  
  
  RESULTS
  We showed in vitro and in vivo that CK2 phosphorylation was involved in the nucleocytoplasmic shuttling of SmHMGB1. By site-directed mutagenesis we mapped the two serine residues of SmHMGB1 that were phosphorylated by CK2. By DNA bending and supercoiling assays we showed that CK2 phosphorylation of SmHMGB1 had no effect in the DNA binding activities of the protein. We showed by electron microscopy, as well as by cell transfection and fluorescence microscopy that SmHMGB1 was present in the nucleus and cytoplasm of adult schistosomes and mammalian cells. In addition, we showed that treatments of the cells with either a phosphatase or a CK2 inhibitor were able to enhance or block, respectively, the cellular traffic of SmHMGB1. Importantly, we showed by confocal microscopy and biochemically that SmHMGB1 is significantly secreted by S. mansoni eggs of infected animals and that SmHMGB1 that were localized in the periovular schistosomotic granuloma were phosphorylated.
  
  
  CONCLUSIONS
  We showed that secretion of SmHMGB1 is regulated by phosphorylation. Moreover, our results suggest that egg-secreted SmHMGB1 may represent a new egg antigen. Therefore, the identification of drugs that specifically target phosphorylation of SmHMGB1 might block its secretion and interfere with the pathogenesis of schistosomiasis.
authors: Instituto de Bioquímica Médica, Programa de Biologia Molecular e Biotecnologia, Universidade Federal do Rio de Janeiro, Ilha do Fundão, Rio de Janeiro, Brasil.
authors: Isabel Caetano
authors: IC
authors: de Abreu da Silva
authors: Vitor Coutinho
authors: VC
authors: Carneiro
authors: Renata de Moraes
authors: Rde M
authors: Maciel
authors: Rodrigo Furtado Madeiro
authors: RF
authors: da Costa
authors: Daniel Rodrigues
authors: DR
authors: Furtado
authors: Francisco Meirelles Bastos
authors: FM
authors: de Oliveira
authors: Mário Alberto Cardoso
authors: MA
authors: da Silva-Neto
authors: Franklin David
authors: FD
authors: Rumjanek
authors: Marcelo Rosado
authors: MR
authors: Fantappié
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D047390:Casein Kinase II / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D003600:Cytosol / Q000378:metabolism; D016054:DNA, Protozoan / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D057075:Enzyme Assays; D005260:Female; D006099:Granuloma / Q000378:metabolism; D024243:HMGB1 Protein / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008099:Liver / Q000378:metabolism / Q000469:parasitology / Q000473:pathology / Q000648:ultrastructure; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D060066:Protein Interaction Maps; D012550:Schistosoma mansoni / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D016054:DNA, Protozoan; D004278:DNA, Superhelical; D024243:HMGB1 Protein; D047390:Casein Kinase II