Light- and electron-microscopical study of phosphoprotein B-50 following denervation and reinnervation of the rat soleus muscle.
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.
Verhaagen
J
J
Department of Neurology, University Hospital, Utrecht, The Netherlands.
Oesteicher
A B
AB
Edwards
P M
PM
Veldman
H
H
Jennekens
F G
FG
Gispen
W H
WH
D000110:Acetylcholinesterase / Q000378:metabolism; D000818:Animals; D005260:Female; D019922:GAP-43 Protein; D006614:Hindlimb; D007150:Immunohistochemistry; D007158:Immunologic Techniques; D008854:Microscopy, Electron; D009121:Muscle Denervation; D009132:Muscles / Q000201:enzymology / Q000294:innervation*; D009416:Nerve Regeneration; D010750:Phosphoproteins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D019922:GAP-43 Protein; D010750:Phosphoproteins; D000110:Acetylcholinesterase