Diminished neuromuscular junction immunoreactivity of Amyotrophic lateral sclerosis sera in mice lacking P/Q-type calcium channels

L. GONZALEZ; M. KOTLER; V. SANCHEZ; R. REISIN; O. UCHITEL

Chicago

Congreso; Society for Neuroscience, 2009.; 2009

Amyotrophic Lateral Sclerosis (ALS) is an invariably fatal neurodegenerative disease that is characterized by a progressive loss of both superior and inferior motoneurons. The vast majority of ALS cases (90%) belongs to a sporadic form whose etiology remains unknown.Previous results from our laboratory (J. Neurosci. 26(10):2661,2006) favor an autoimmune hypothesis as a possible cause for sporadic ALS. With the aim of gaining knowledge about the potential antigens that interact with Immunoglobulins G from sporadic ALS patients (ALS-IgG), we studied their immunoreactivity against NMJ of normal mice and those lacking P/Q- and N-type calcium channels.We isolated Immunoglobulins G (IgGs) from ALS patients’ sera by affinity chromatography and characterized them by immunofluorescence followed by confocal microscopy analysis.In approximately 50% of cases (5 out of 9), ALS-IgGs presented an important immunoreactivity against neuromuscular junctions of mouse diaphragm, colocalizing with Acetylcholine Receptor, a post-synaptic membrane marker of that structure. The representative fluorescence intensity (rfi) for ALS-IgGs was 3.97±0.76 whereas for control patients it was 1.76±0.54 (p<0.01, N=3). Additionally 4 out of 5 of these sera showed a significant decrease in their interaction with NMJ of mice lacking P/Q-type calcium channels (rfi: 2.72±0.29, p<0.001, N=2), reaching levels comparable with the isotype control (rfi: 2.31±0.38). This difference in reactivity was totally absent when N-type calcium channel wild-type and knock-out mice were compared (rfi: 16.47±1.18 for WT and 17.35±1.27 for KO, N=2).The results found in this research add evidence in favor of the autoimmune hypothesis as one of the possible causes of ALS. They also suggest that serum of some patients possesses auto-antibodies that would interact with proteins whose expression is diminished in mice lacking P/Q-type calcium channels.