title: Potentiation of NMDA receptor-dependent cell responses by extracellular high mobility group box 1 protein.
abstract: BACKGROUND
  Extracellular high mobility group box 1 (HMGB1) protein can operate in a synergistic fashion with different signal molecules promoting an increase of cell Ca(2+) influx. However, the mechanisms responsible for this effect of HMGB1 are still unknown.
  
  
  RESULTS
  Here we demonstrate that, at concentrations of agonist per se ineffective, HMGB1 potentiates the activation of the ionotropic glutamate N-methyl-D-aspartate receptor (NMDAR) in isolated hippocampal nerve terminals and in a neuroblastoma cell line. This effect was abolished by the NMDA channel blocker MK-801. The HMGB1-facilitated NMDAR opening was followed by activation of the Ca(2+)-dependent enzymes calpain and nitric oxide synthase in neuroblastoma cells, resulting in an increased production of NO, a consequent enhanced cell motility, and onset of morphological differentiation. We have also identified NMDAR as the mediator of HMGB1-stimulated murine erythroleukemia cell differentiation, induced by hexamethylenebisacetamide. The potentiation of NMDAR activation involved a peptide of HMGB1 located in the B box at the amino acids 130-139. This HMGB1 fragment did not overlap with binding sites for other cell surface receptors of HMGB1, such as the advanced glycation end products or the Toll-like receptor 4. Moreover, in a competition assay, the HMGB1((130-139)) peptide displaced the NMDAR/HMGB1 interaction, suggesting that it comprised the molecular and functional site of HMGB1 regulating the NMDA receptor complex.
  
  
  CONCLUSIONS
  We propose that the multifunctional cytokine-like molecule HMGB1 released by activated, stressed, and damaged or necrotic cells can facilitate NMDAR-mediated cell responses, both in the central nervous system and in peripheral tissues, independently of other known cell surface receptors for HMGB1.
authors.affiliation: Department of Experimental Medicine (DIMES) University of Genova, Genova, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Pedrazzi
authors.forename: Monica
authors.initials: M
authors.lastname: Averna
authors.forename: Bianca
authors.initials: B
authors.lastname: Sparatore
authors.forename: Mauro
authors.initials: M
authors.lastname: Patrone
authors.forename: Franca
authors.initials: F
authors.lastname: Salamino
authors.forename: Manuela
authors.initials: M
authors.lastname: Marcoli
authors.forename: Guido
authors.initials: G
authors.lastname: Maura
authors.forename: Chiara
authors.initials: C
authors.lastname: Cervetto
authors.forename: Daniela
authors.initials: D
authors.lastname: Frattaroli
authors.forename: Sandro
authors.initials: S
authors.lastname: Pontremoli
authors.forename: Edon
authors.initials: E
authors.lastname: Melloni
mesh_terms: D000081:Acetamides / Q000494:pharmacology; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism*; D024243:HMGB1 Protein / Q000494:pharmacology*; D006801:Humans; D008297:Male; D051379:Mice; D016202:N-Methylaspartate / Q000494:pharmacology; D016501:Neurites / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D017729:Presynaptic Terminals / Q000187:drug effects / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D014316:Tritium
chemical_list: D000081:Acetamides; D024243:HMGB1 Protein; D016194:Receptors, N-Methyl-D-Aspartate; D014316:Tritium; D001224:Aspartic Acid; D009569:Nitric Oxide; D016202:N-Methylaspartate; D052248:Nitric Oxide Synthase Type I; C014026:hexamethylene bisacetamide; D002118:Calcium