title: Sera from amyotrophic lateral sclerosis patients induce the non-canonical activation of NMDA receptors "in vitro".
abstract: Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by the selective loss of both upper and lower motoneurons (MNs). The familial form of the illness is associated with mutations in the gene encoding Cu/Zn superoxide dismutase 1 (SOD-1) enzyme, but it accounts for fewer than 10% of cases; the rest, more than 90%, correspond to the sporadic form of ALS. Although many proposals have been suggested over the years, the mechanisms underlying the characteristic selective killing of MN in ALS remain unknown. In this study we tested the effect of sera from sporadic ALS patients on NMDA receptors (NMDAR). We hypothesize that an endogenous seric factor is implicated in neuronal death in ALS, mediated by the modulation of NMDAR. Sera from ALS patients and from healthy subjects were pretreated to inactivate complement pathways and dialyzed to remove glutamate and glycine. IgGs from ALS patients and healthy subjects were obtained by affinity chromatography and dialyzed against phosphate-buffered saline. Human NMDAR were expressed in Xenopus laevis oocytes, and ionic currents were recorded using the two-electrode voltage clamp technique. Sera from sporadic ALS patients induced transient oscillatory currents in oocytes expressing NMDAR with a significantly higher total electrical charge than that induced by sera from healthy subjects. Sera from patients with other neuromuscular diseases did not exert this effect. The currents were inhibited by MK-801, a noncompetitive blocker of NMDAR. The PLC inhibitor, U-73122, and the IP(3) receptor antagonist, 2-APB, also inhibited the sera-induced currents. The oscillatory signal recorded was due to internal calcium mobilization. Isolated IgGs from ALS patients significantly affected the activity of oocytes injected with NMDAR, causing a 2-fold increase over the response recorded for IgGs from healthy subjects. Our data support the notion that ALS sera contain soluble factors that mobilize intracellular calcium, not opening directly the ionic conductance, but through the non-canonical activation of NMDAR.
authors.affiliation: Laboratory of Cellular and Molecular Neurobiology, Department of Pathology and Experimental Therapeutics, Medical School-Bellvitge Campus, University of Barcelona, C/Feixa Llarga s/n, L'Hospitalet de Llobregat, E-08907 Barcelona, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Texidó
authors.forename: Sara
authors.initials: S
authors.lastname: Hernández
authors.forename: Mireia
authors.initials: M
authors.lastname: Martín-Satué
authors.forename: Mònica
authors.initials: M
authors.lastname: Povedano
authors.forename: Anna
authors.initials: A
authors.lastname: Casanovas
authors.forename: Josep
authors.initials: J
authors.lastname: Esquerda
authors.forename: Jordi
authors.initials: J
authors.lastname: Marsal
authors.forename: Carles
authors.initials: C
authors.lastname: Solsona
mesh_terms: D000328:Adult; D000368:Aged; D000690:Amyotrophic Lateral Sclerosis / Q000097:blood* / Q000503:physiopathology*; D000818:Animals; D001798:Blood Proteins / Q000633:toxicity*; D020013:Calcium Signaling / Q000187:drug effects* / Q000502:physiology; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005260:Female; D018698:Glutamic Acid / Q000502:physiology / Q000633:toxicity; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009410:Nerve Degeneration / Q000139:chemically induced / Q000503:physiopathology; D009498:Neurotoxins / Q000633:toxicity; D009865:Oocytes; D016194:Receptors, N-Methyl-D-Aspartate / Q000819:agonists* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D014982:Xenopus laevis
chemical_list: D001798:Blood Proteins; D018690:Excitatory Amino Acid Agonists; D009498:Neurotoxins; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid