RETROGRADE AXONAL-TRANSPORT OF THE ALPHA-SUBUNIT OF THE GTP-BINDING PROTEIN G(Z) IN MOUSE SCIATIC-NERVE - A POTENTIAL PATHWAY FOR SIGNAL-TRANSDUCTION IN NEURONS

We have utilized antibodies against the a subunit of G(z) in fluorescence immunohistochemistry to determine whether this GTP-binding protein can translocate along nerves by intra-axonal transport. After ligation of the mouse sciatic nerve we found an increase in G(z)-like immunoreactivity on the proximal and distal side with time, suggesting that the alpha subunit undergoes orthograde axonal transport and also returns to the cell body by retrograde axonal transport in the sciatic nerve. Unlike the retrograde transport of G(i alpha), shown in a previous study to be present in most sciatic axons, G(z alpha) only accumulated in a subpopulation of axons, suggesting that different G-proteins could convey information specific to neuronal subtypes. These results support our proposal that G(z) may play a second messenger role in communicating information from the terminals back to cell bodies. G(i alpha) and G(z alpha) may be representative of relatively stable signalling molecules by which the signal from some neurotrophic molecules can be translocated from the neuronal periphery to the cell body without the need for the retrograde transport of the neurotrophic factor itself.