Light- and electron-microscopical study of phosphoprotein B-50 following denervation and reinnervation of the rat soleus muscle

Abstract

The neuron-specific phosphoprotein B-50 was originally identified as a phosphoprotein in synaptic plasma membranes isolated from adult brain tissue. In this paper we study the reinnervation of the soleus muscle, a target muscle of sciatic nerve axons, using affinity-purified anti-B-50 antibodies. Light-microscopical evaluation of the reinnervation process revealed that the period of muscle fiber reinnervation corresponds closely with the time in which high B-50 immunoreactivity was observed in the nerve fibers that invade the muscle and in the newly formed neuromuscular junctions. Upon completion of reinnervation, B-50 immunoreactivity decreased. In the newly innervating terminals, B-50 was associated with presynaptic vesicular structures and with the presynaptic plasma membrane. In intact mature neuromuscular junctions, virtually no B-50 immunoreactivity could be detected with either light- or electron-microscopic procedures. These observations corroborate the association of high levels of B-50/GAP43 during axon outgrowth and support the concept that B-50 may be a key molecule in the reconstruction of axonal structures. We also observed an unexpected transient increase in B-50 immunoreactivity in the degenerating neuromuscular junctions. This observation cannot be explained in terms of increased neuronal synthesis of B-50, since the degenerating axon processes have been completely disconnected from their cell bodies. Thus, our evidence implies that a rise of B-50 immunoreactivity can be associated with stages of neuronal degeneration as well as with those of neuronal differentiation and axon outgrowth.

Directed expression of the growth-associated protein B-50/GAP-43 to olfactory neurons in transgenic mice results in changes in axon morphology and extraglomerular fiber growth

“…Separated proteins were transferred to nitrocellulose membranes (Towbin et al, 1984). The membrane was preincubated in TBS/gelatin/TX-100 (TBS containing 0.25% gelatin and 0.5% Triton X-100) and immunostained with polyclonal antibodies (derived from antiserum #8921; Oestreicher et al, 1983) against B-50/GAP-43 (dilution 1: 1000) under standard conditions (Verhaagen et al, 1988).…”

“…It is expressed at high levels in the developing nervous system (Biffo et al, 1990;Dani et al, 1991) and is induced after nerve injury (Benowitz et al, 1981;Skene and Willard 1981a,b;Verhaagen et al, 1988). A role of B-50/ in nerve fiber outgrowth is controversial and has been the subject of intense study.…”

Expression of growth-associated protein B-50 (GAP43) in dorsal root ganglia and sciatic nerve during regenerative sprouting

“…The GAPS, like B-50, have been implicated in axonal repair processes as well (Skene and Willard 198 1;Benowitz et al, 198 1;Benowitz and Lewis, 1983). The protein is expressed in regenerating axons following mechanical damage of the sciatic nerve in the rat (Verhaagen et al, 1986) and is present in the presynaptic terminal of newly formed neuromuscular junctions (Verhaagen et al, 1988).…”

Changes in innervation of long bones after insertion of an implant: Immunocytochemical study in goats with antibodies to calcitonin gene‐related peptide and B‐50/GAP‐43

“…thus, the antibody may be of use to demonstrate axHowever, it also seems very plausible that CGRP plays onal sprouting (11,49,53). The purpose of this study was to describe the changes in the pattern of sensory innervation in bone after insertion of an implant.…”

“…Innervation may be in- (29,30,46), may be of special interest in innervavolved in trophic effects on tissues, regulation of tion studies. This antibody has been applied to detect vascularization or bone remodeling, and pain and pro prioception (2, 3,19,26), outgrowing nerve fibres (48,52,53). A high concen tration of B-50/GAP-43 has been found in axonal The present study focussed on the changes in the growth cones during embryonic (37,50) and post innervation pattern of sensory fibres associated with natal development (10,11,39).…”