The neuropathic potential of anti-GM1 autoantibodies is regulated by the local glycolipid environment in mice
Kay N. Greenshields, … , Jaap J. Plomp, Hugh J. Willison
Kay N. Greenshields, … , Jaap J. Plomp, Hugh J. Willison
Published February 16, 2009
Citation Information: J Clin Invest. 2009;119(3):595-610. https://doi.org/10.1172/JCI37338.
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Research Article Neuroscience

The neuropathic potential of anti-GM1 autoantibodies is regulated by the local glycolipid environment in mice

Abstract

Anti-GM1 ganglioside autoantibodies are used as diagnostic markers for motor axonal peripheral neuropathies and are believed to be the primary mediators of such diseases. However, their ability to bind and exert pathogenic effects at neuronal membranes is highly inconsistent. Using human and mouse monoclonal anti-GM1 antibodies to probe the GM1-rich motor nerve terminal membrane in mice, we here show that the antigenic oligosaccharide of GM1 in the live plasma membrane is cryptic, hidden on surface domains that become buried for a proportion of anti-GM1 antibodies due to a masking effect of neighboring gangliosides. The cryptic GM1 binding domain was exposed by sialidase treatment that liberated sialic acid from masking gangliosides including GD1a or by disruption of the live membrane by freezing or fixation. This cryptic behavior was also recapitulated in solid-phase immunoassays. These data show that certain anti-GM1 antibodies exert potent complement activation-mediated neuropathogenic effects, including morphological damage at living terminal motor axons, leading to a block of synaptic transmission. This occurred only when GM1 was topologically available for antibody binding, but not when GM1 was cryptic. This revised understanding of the complexities in ganglioside membrane topology provides a mechanistic account for wide variations in the neuropathic potential of anti-GM1 antibodies.

Authors

Kay N. Greenshields, Susan K. Halstead, Femke M.P. Zitman, Simon Rinaldi, Kathryn M. Brennan, Colin O’Leary, Luke H. Chamberlain, Alistair Easton, Jennifer Roxburgh, John Pediani, Koichi Furukawa, Keiko Furukawa, Carl S. Goodyear, Jaap J. Plomp, Hugh J. Willison

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Figure 2

Pathophysiological effects of anti-GM1 antibodies in living nerve-muscle preparations ex vivo.

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Pathophysiological effects of anti-GM1 antibodies in living nerve-muscle...
(A) Reconstructed confocal images of triangularis sterni NMJs from GD3s–/– mice, following ex vivo incubation in CTB, DG2, and DG1. For CTB and DG2, axonal staining is present along with staining of the parajunctional fibroblast. DG1 binding is undetectable. (B) Electrophysiology in ex vivo hemidiaphragm of WT and GD3s–/– mice. mAbs were applied, followed by a source of complement, and under such conditions only DG2 caused an increase in MEPP frequency of each strain. Con, control. (C) DG1 effect in ex vivo hemidiaphragm (WT and GD3s–/–). Following ex vivo muscle nerve incubations in mAb (or Ringer’ s medium alone [R] as control), tissue was snap-frozen and sectioned for quantitative analysis. Graphs show IgG, C3c, and MAC deposition (quantified as the signal intensity over the NMJ). Neurofilament (NF) loss is quantified as area coverage over the NMJ. DG1 binding is undetectable in the WT NMJ and only weakly present in the GD3s–/– NMJ under maximal detection settings. MAC and C3c deposition do not translate into neurofilament loss. (D) The experiment was performed as described for C, but with the mAb DG2. DG2 is detectable in WT and GD3s–/– NMJs and activates complement to cause a neurofilament loss compared with Ringer’s medium alone–incubated control tissue. For both C and D, note that the y axes have been adjusted for clarity. *P < 0.05 compared with the Ringer’s control. Scale bars: 20 μm.