Immunoglobulins G from patients with sporadic amyotrophic lateral sclerosis affects cytosolic Ca2+ homeostasis in cultured rat astrocytes

Abstract

Astrocytes are considered essential in the etiopathogenesis of amyotrophic lateral sclerosis (ALS). We have demonstrated previously that immunoglobulins G (IgG) isolated from patients with ALS enhance the mobility of acidic vesicles in cultured astrocytes in a Ca2+-dependent manner. Here we directly examined the impact of purified sporadic ALS IgG on cytosolic [Ca2+] ([Ca2+]i) in astrocytes. Confocal time-lapse images were acquired and fluorescence of a non-ratiometric Ca2+ indicator was recorded before and after the application of IgG. ALS IgG (0.1mg/ml) from 7 patients evoked transient increases in [Ca2+]i in ~50% of tested astrocytes. The probability of observing a response was independent of extracellular Ca2+. The peak increase in [Ca2+]i developed ~3 times faster and the time integral of evoked transients was ~2-fold larger; the peak amplitude itself was not affected by extracellular Ca2+. Application of pharmacological inhibitors revealed that activation of inositol-1,4,5-triphosphate receptors is necessary and sufficient to initiate transients in [Ca2+]i; the Ca2+ influx through store-operated calcium entry prolongs the transient increase in [Ca2+]i. Thus, ALS IgG acutely affect [Ca2+]i by mobilizing both, intra- and extracellular Ca2+ into the cytosol of cultured astrocytes.