Scorpion toxins to unravel the conundrum of ion channel structure and functioning

The consequences of scorpion stings on the affected victims, including humans, have been known since ancient times. The effects of the venom, first on neurotransmission and thereafter on many physiological processes at the organism, tissue, cellular or molecular levels, have been the subject of intense research. It is, therefore, not surprising that a large number of toxins acting on a variety of ion channels have been isolated and described to date. Many of these toxins show high specificities and affinities towards their natural targets. Along with their own biochemical and biophysical characterization, scorpion toxins have been used as invaluable tools for studies regarding the structure and function of ion channels. They have also become important leads in drug development aiming at diagnosing, targeting or direct treatment of channelopathies caused by the improper function of those channels they recognize, as well as other anomalous physiological conditions, including autoimmune diseases and cancer. The main families of scorpion toxins are reviewed here, among which are those specific for Na⁺, K⁺ and ryanodine-sensitive Ca²⁺ channels. The focus is placed on the historical events that led to their discovery and their use in the identification and characterization of the structure and function of ion channels. Their potential use in medicine is also presented.