Australian Scorpion Venom Fractions Show Broad Bioactivity Through Modulation of Bio-Impedance and Cytosolic Calcium.

Scorpion venoms are a rich source of bioactive molecules, but characterisation of toxin peptides affecting cytosolic Ca, central to cell signalling and cell death, is limited. We undertook a functional screening of the venom of the Australian scorpion to determine the breadth of Ca mobilisation. A human embryonic kidney (HEK293) cell line stably expressing the genetically encoded Ca reporter GCaMP5G and the rabbit type 1 ryanodine receptor (RyR1) was developed as a biosensor. Size-exclusion Fast Protein Liquid Chromatography separated the venom into 53 fractions, constituting 12 chromatographic peaks. Liquid chromatography mass spectroscopy identified 182 distinct molecules with 3 to 63 components per peak. The molecular weights varied from 258 Da-13.6 kDa, with 53% under 1 kDa. The majority of the venom chromatographic peaks (tested as six venom pools) were found to reversibly modulate cell monolayer bioimpedance, detected using the xCELLigence platform (ACEA Biosciences). Confocal Ca imaging showed 9/14 peak samples, with molecules spanning the molecular size range, increased cytosolic Ca mobilization. venom Ca activity was correlated with changes in bio-impedance, reflecting multi-modal toxin actions on cell physiology across the venom proteome.