The effect of amyotrophic lateral sclerosis-linked exogenous SOD1-G93A on electrophysiological properties and intracellular calcium in cultured rat astrocytes

Abstract

Over 150 mutations in the SOD1 gene that encodes Cu/Zn superoxide dismutase (SOD1) cause 20–25% of familial ALS, albeit without a known gain-of-function mechanism. ALS is also non-cell-autonomous, the interactions between motor neurons and their glial neighbours being implicated in disease progression. The aim here was to investigate the biophysical effects of the exogenous human mutant SOD1-G93A on rat astrocytes in culture. Primary cortical astrocyte cultures were treated with recombinant human apo- mSOD1-G93A vs. wild-type control (wtSOD1) and recorded by patch-clamp and calcium imaging. Results showed that exogenous mSOD1 as well as wtSOD1 induced a decrease of membrane resistance, the effect being persistent (up to 13 min) only for the mutant form. Similarly, whole-cell inward currents in astrocytes were augmented by both wt and mSOD1, but the effect was twice larger and only progressed continuously for the latter. Both forms of SOD1 also induced a rise in intracellular Ca²⁺ activity, the effect being dependent on external Ca²⁺ and again only persisted with mSOD1, becoming significantly different from wtSOD1 only at longer times (14 min). In conclusion, this study points to membrane permeability and Ca²⁺ signalling as processes affected by SOD1-G93A that presents the humoral factor triggering the role of astrocytes in ALS pathophysiology.

Key words:

• ALS
• exogenous superoxide dismutase
• cultured astrocytes
• membrane resistance
• transmembrane currents
• Ca²⁺ imaging

Acknowledgements

The authors are grateful to Jean Pierre Julien for the gift of recombinant mSOD1 and to Aleksandar Bajić for help in setting up initial experiments on Ca²⁺ imaging. The study was supported by the MESTD RS grant no III41005. MESTD RS was not involved in study design; in the collection, analysis and interpretation of data; in the writing of the report; or in the decision to submit the article for publication.

Declaration of interest

The authors declare no conflicts of interest.