RETROGRADE AXONAL-TRANSPORT OF SIGNAL-TRANSDUCTION PROTEINS IN RAT SCIATIC-NERVE

Neurons require a mechanism to transmit stable signals over the large distance from the nerve growth cone or terminal to the cell body, in o rder that information from the target tissue can be relayed to the cel l body where it is required. Nerve growth factor (NGF), a target-deriv ed neurotrophic factor, is thought to signal over this distance by rec eptor mediated internalization of NGF, followed by retrograde axonal t ransport of the NGF-receptor complex. In this paper we show, by immuno histochemistry of rat sciatic nerve, accumulation of phosphotyrosine i mmunoreactivity only on the distal side of a nerve crush, suggesting a xonal transport of tyrosine kinases and/or tyrosine phosphorylated pro teins primarily in a retrograde direction. Furthermore, we also show r etrograde axonal transport of phosphoinositide 3-kinase, ERK, MEK and MEK kinase, of which all but MEK kinase are known to be activated down stream of tyrosine receptor kinase activation. The retrograde transpor t of these proteins suggests that they may be involved in transmission of signals along the axon, relaying neurotrophic factor receptor acti vation at the nerve terminal to the nerve cell body.