Presenilin-1 and its N-terminal and C-terminal fragments are transported in the sciatic nerve of rat

Abstract

The axonal transport of presenilin-1 was investigated in a spinal cord-sciatic nerve-neuromuscular junction model system in the rat. The technique of unilateral sciatic nerve ligation, using double ligatures, was combined with immunohistochemical staining and Western blotting to examine the axonal transport of the protein. Immunohistochemical studies involving the use of polyclonal antibodies for either the N-terminal or the C-terminal domain of presenilin-1 furnished evidence that both fragments may be present not only in the neuronal cell bodies, but also in the motoric and sensory axons and the motoric axon terminals at the neuromuscular junctions. After double ligation of the sciatic nerve for 6, 12 or 24 h, progressive immunostaining of presenilin-1 occurred above the upper ligature and to a lesser extent below the lower ligature. Double staining of the sciatic nerve for presenilin-1 and for amyloid precursor protein revealed overlapping immunoreactivity. Western blotting confirmed the accumulation of the approximately 20-kDa C-terminal and approximately 25-kDa N-terminal fragments and the full-length 45-kDa holoprotein of presenilin-1 both above and below the ligature. It is concluded that besides the larger amounts of C-terminal and N-terminal fragments, a smaller quantity of intact presenilin-1 may be present and conveyed bidirectionally in the sciatic nerve of the rat. These results lend further support to the suggestion that presenilin-1 may leave the trans-Golgi network and be found in the axons and axon terminals of the various neurons.