Assembly and regulation of acetylcholinesterase at the vertebrate neuromuscular junction

R. L. Rotundo, C. A. Ruiz, E. Marrero, L. M. Kimbell, S. G. Rossi, T. Rosenberry, A. Darr, P. Tsoulfas

Research output: Contribution to journalArticle

19 Scopus citations

Abstract

The collagen-tailed form of acetylcholinesterase (ColQ-AChE) is the major if not unique form of the enzyme associated with the neuromuscular junction (NMJ). This enzyme form consists of catalytic and non-catalytic subunits encoded by separate genes, assembled as three enzymatic tetramers attached to the three-stranded collagen-like tail (ColQ). This synaptic form of the enzyme is tightly attached to the basal lamina associated with the glycosaminoglycan perlecan. Fasciculin-2 is a snake toxin that binds tightly to AChE. Localization of junctional AChE on frozen sections of muscle with fluorescent Fasciculin-2 shows that the labeled toxin dissociates with a half-life of about 36 h. The fluorescent toxin can subsequently be taken up by the muscle fibers by endocytosis giving the appearance of enzyme recycling. Newly synthesized AChE molecules undergo a lengthy series of processing events before final transport to the cell surface and association with the synaptic basal lamina. Following co-translational glycosylation the catalytic subunit polypeptide chain interacts with several molecular chaperones, glycosidases and glycosyltransferases to produce a catalytically active enzyme that can subsequently bind to one of two non-catalytic subunits. These molecular chaperones can be rate limiting steps in the assembly process. Treatment of muscle cells with a synthetic peptide containing the PRAD attachment sequence and a KDEL retention signal results in a large increase in assembled and exportable AChE, providing an additional level of post-translational control. Finally, we have found that Pumilio2, a member of the PUF family of RNA-binding proteins, is highly concentrated at the vertebrate neuromuscular junction where it plays an important role in regulating AChE translation through binding to a highly conserved NANOS response element in the 3′-UTR. Together, these studies define several new levels of AChE regulation in electrically excitable cells.

Original languageEnglish (US)
Pages (from-to)26-29
Number of pages4
JournalChemico-Biological Interactions
Volume175
Issue number1-3
DOIs
StatePublished - Sep 25 2008

Keywords

  • AChE assembly
  • AChE turnover
  • Fasciculin-2
  • Molecular chaperones
  • Protein folding
  • RNA-binding protein
  • Synapse
  • Translational regulation

ASJC Scopus subject areas

  • Toxicology

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    Rotundo, R. L., Ruiz, C. A., Marrero, E., Kimbell, L. M., Rossi, S. G., Rosenberry, T., Darr, A., & Tsoulfas, P. (2008). Assembly and regulation of acetylcholinesterase at the vertebrate neuromuscular junction. Chemico-Biological Interactions, 175(1-3), 26-29. https://doi.org/10.1016/j.cbi.2008.05.025