KLOSE, M.K.*; ROBERTSON, R.M.; Queen’s University: Heat Shock-Mediated Thermoprotection of Insect Neuromuscular Junctions

Protection of cells and circuits from the deleterious effects of various environmental stresses can be induced after a brief initial stressful insult such as a heat shock or anoxic shock. The goal of this project is to understand the mechanisms involved in mediating stress protection. The first step is to determine the site(s) at which protection is conferred. A post-synaptic site of heat-shock induced protection has been suggested by experiments in which miniture excitatory junctional currents were recorded. A more reliable way to confirm post-synaptic involvement in protection would be to examine the stress tolerance of potentials induced by iontophoresis of L-glutamate directly onto post-synaptic receptors. During iontophoresis desensitization of glutamate receptors can be prevented with concanavalin A (Con A). To ensure that Con A would not alter heat shock induced protection or induce protection itself, control experiments were performed. Surprisingly, Con A induced thermoprotection which mimicked protection induced by heat shock. Con A stabilizes receptors on cell surfaces by cross-linkage, anchoring them in place. Stress can alter structural elements within cells and the cytoskeleton is one of the most sensitive targets. Experiments using the cytoskeletal disrupting agents cytochalasin B and colchicine, which interfere with Con A-induced anchoring of receptors, revealed effects on thermoprotection. This suggests that structural stabilization of receptor in the membrane could be involved in mediating thermoprotection. Concanavalin A-induced thermoprotection may provide a valuable model for uncovering mechanisms of stress-induced thermoprotection at synapses.