Autoimmune recognition profile of the alpha chain of human acetylcholine receptor in myasthenia gravis

Immunoglobulins from motoneurone disease patients enhance glutamate release from rat hippocampal neurones in culture

1. The whole-cell configuration of the patch-clamp technique was used to study the effects of immunoglobulins (IgGs) from patients affected by amyotrophic lateral sclerosis (ALS) on spontaneous glutamatergic currents in rat hippocampal cells in culture. 2. Focal application of ALS IgGs (100 micrograms ml-1) to hippocampal cells induced a rise in frequency but not in amplitude of spontaneous excitatory postsynaptic currents (SEPSC) which outlasted the period of IgG application. The mean frequency ratio (ALS over control) was 3.2 +/- 0.6 (n = 19). No changes in frequency or amplitude of SEPSCs were observed after treatment with IgGs obtained from healthy donors (n = 5) or from patients with Alzheimer's disease (n = 4). 3. ALS IgGs also increased the frequency (by a factor of 2.0 +/- 0.3) but not the amplitude of miniature excitatory postsynaptic currents (mEPSC) recorded in the presence of TTX (n = 19). A rise in frequency of mEPSC was also seen in cells superfused with a calcium-free solution (n = 4). 4. In the presence of TTX, ALS IgGs did not modify the amplitude or the shape of currents evoked by AMPA (100 microM), recorded at a holding potential of -50 mV. 5. It is concluded that ALS IgGs enhance both SEPSCs and mEPSCs through a presynaptic type of action. The excessive release of glutamate from nerve endings may be the cause of motoneurone death in ALS patients.

Amyotrophic lateral sclerosis immunoglobulins increase Ca2+ currents in a motoneuron cell line

The sporadic form of amyotrophic lateral sclerosis (ALS) is an idiopathic and eventually lethal disorder causing progressive degeneration of cortical and spinal motoneurons. Recent studies have shown that the majority of patients with sporadic ALS have serum antibodies that bind to purified L-type voltage-gated calcium channels and that antibody titer correlates with the rate of disease progression. Furthermore, antibodies purified from ALS patient sera have been found to alter the physiologic function of voltage-gated calcium channels in nonmotoneuron cell types. Using whole-cell patch-clamp techniques, immunoglobulins purified from sera of 5 of 6 patients with sporadic ALS are now shown to increase calcium currents in a hybrid motoneuron cell line, VSC4.1. These calcium currents are blocked by the polyamine funnel-web spider toxin FTX, which has previously been shown to block Ca2+ currents and evoked transmitter release at mammalian motoneuron terminals. These data provide additional evidence linking ALS to an autoimmune process and suggest that antibody-induced increases in calcium entry through voltage-gated calcium channels may occur in motoneurons in this disease, with possible deleterious effects in susceptible neurons.

Amyotrophic lateral sclerosis patient antibodies label Ca2+ channel alpha 1 subunit

Sporadic amyotrophic lateral sclerosis is an idiopathic human degenerative disease of spinal cord and brain motor neurons. Prior studies demonstrated that most patients with amyotrophic lateral sclerosis possess immunoglobulins that bind to purified L-type voltage-gated calcium channels, that titers of anti-voltage-gated calcium channel antibodies correlate with disease progression rates, and that amyotrophic lateral sclerosis patient-derived antibodies (ALS IgG) produce electrophysiological changes in the function of voltage-gated calcium channels. Using Western transfer immunoblots and enzyme-linked immunosorbent assays, the calcium ionophore-forming alpha 1 subunit of the voltage-gated calcium channel is now identified as the major voltage-gated calcium channel antigen to which ALS IgG binds. Additionally, the binding of an L-type voltage-gated calcium channel alpha 1 subunit-directed monoclonal antibody, which itself mimics the effects of ALS IgG on skeletal muscle voltage-gated calcium channel currents, is selectively prevented by preaddition of ALS IgG. Voltage-gated calcium channel-binding IgG from patients with Lambert-Eaton myasthenic syndrome appears to be differentiated from ALS IgG by the reactivity of the former to both alpha 1 and beta subunits of the calcium channel. These assays provide further evidence linking amyotrophic lateral sclerosis to an autoimmune process, and suggest one means to differentiate immunoglobulins from patients with amyotrophic lateral sclerosis from those of patients with another autoimmune disease expressing calcium channel antibodies.