Heat stress induces changes in protein synthesis and fast axonal transport in bullfrog sensory neurons

The effects of heat stress on protein synthesis and fast axonal transport were examined in an in vitro bullfrog primary afferent neuron preparation. The magnitude of effect was determined for individual [35S]methionine-labelled protein species separated via two-dimensional gel electrophoresis. Elevation of temperature of the preparation from 18 degrees C to 33 degrees C caused a transient inhibition of synthesis of non-heat-shock proteins, whereas the synthesis of a 74,000-dalton protein increased to 927% of controls after 4 h. Similar prolonged stress conditions had no effect on the relative abundance of 36 individual, newly synthesized proteins undergoing fast axonal transport. A dramatic exception was represented by a 55,000-dalton glycoprotein whose fast transport was increased to 291% of control. The increase in transport of this protein during a time when synthesis and transport of other non-heat-shock proteins were not enhanced suggests that it may play a unique role in the early cellular events that mediate survival or thermotolerance in the neuron.