Journal of Neuroscience, Vol 12, 1602-1615, Copyright © 1992 by Society for Neuroscience
Developmental and neural regulation of a subsarcolemmal component of the rat neuromuscular junction
SH Astrow, LA Sutton and WJ Thompson
Center for Developmental Biology, University of Texas, Austin 78712.
We have generated a monoclonal antibody, designated mAb 3G2, which reacts
with a subsarcolemmal component of the neuromuscular junction in adult
rats. mAb 3G2 immunoreactivity lies beneath and between the ACh
receptor-rich synaptic gutters, around the sole plate nuclei, and at/near
sarcomeric Z-disks in the vicinity of the synapse. Localization of mAb 3G2
immunoreactivity to neuromuscular junctions begins postnatally and
gradually increases to adult levels. The establishment of this synaptic
localization is neurally regulated, as neonatal denervation prevents its
occurrence. In adults, denervation results in a loss of synaptic
immunoreactivity that returns upon reinnervation. The antigen is also found
at the myotendinous junction; its localization here is innervation
independent. mAb 3G2 recognizes a 41 kDa protein on immunoblots of extracts
of newborn muscle. Based on its distribution within muscle fibers, its
developmental and neural regulation, and its molecular weight, the protein
recognized by mAb 3G2 can be distinguished from other known postsynaptic
proteins. Its neural dependence and developmental regulation suggest that
it may participate in synaptic stabilization, perhaps as the intracellular
component in a chain of proteins that serve to tether the nerve terminal to
the perijunctional region of the muscle fiber.