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J. Cell Biol.,
Volume 145, Number 4, May 17, 1999 911-921
* Department of Cell Biology and Anatomy and Formation of the synaptic basal lamina at
vertebrate neuromuscular junction involves the accumulation of numerous specialized extracellular matrix
molecules including a specific form of acetylcholinesterase (AChE), the collagenic-tailed form. The mechanisms responsible for its localization at sites of nerve-
muscle contact are not well understood. To understand
synaptic AChE localization, we synthesized a fluorescent conjugate of fasciculin 2, a snake Curriculum in Neurobiology, University of North Carolina, Chapel Hill, North
Carolina 27599-7090; and § University of Miami School of Medicine, Miami, Florida 33136
-neurotoxin that
tightly binds to the catalytic subunit. Prelabeling AChE on the surface of Xenopus muscle cells revealed that
preexisting AChE molecules could be recruited to form
clusters that colocalize with acetylcholine receptors at
sites of nerve-muscle contact. Likewise, purified avian
AChE with collagen-like tail, when transplanted to Xenopus muscle cells before the addition of nerves, also
accumulated at sites of nerve-muscle contact. Using exogenous avian AChE as a marker, we show that the
collagenic-tailed form of the enzyme binds to the heparan-sulfate proteoglycan perlecan, which in turn binds
to the dystroglycan complex through -dystroglycan.
Therefore, the dystroglycan-perlecan complex serves
as a cell surface acceptor for AChE, enabling it to be
clustered at the synapse by lateral migration within the
plane of the membrane. A similar mechanism may underlie the initial formation of all specialized basal lamina interposed between other cell types.
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