Friday 7th June 11:00
Sir Neil Chalmers seminar room, Darwin Centre LG16 (below Attenborough studio)
A mouse that snacks on scorpions: evolution of venom resistance in a desert-dwelling murine predator
Depts. of Neurobiology & Integrative Biology, The University of Texas, Austin
The Grasshopper mouse (Onychomys torridus) lives in the Sonoran desert of the American Southwest and is sympatric with the most dangerous scorpion in the USA, the Arizona bark scorpion (Centruroides sculpturatus). Onychomys has evolved resistance to the venom of this scorpion and readily exploits it as a food source. Scorpion venoms are composed of many peptides some of which activate voltage-sensitive sodium channels thereby causing hyperexcitability in their insect prey or vertebrate predators. We have uncovered a novel mechanism by which this mouse has evolved resistance to the pain-inducing peptides of scorpion venom: a single amino acid substitution in the pore of a sodium channel that is expressed selectively in pain-sensing neurons paradoxically co-opts a component of the scorpion venom into a channel pore blocker. In other words, it takes a pain-causing venom peptide and "turns the tables" on the scorpion, by using it as an analgesic to block the pain system.
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