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Originally published In Press as doi:10.1074/jbc.M208664200 on October 23, 2002
J. Biol. Chem., Vol. 277, Issue 52, 50457-50462, December 27, 2002
MuSK Glycosylation Restrains MuSK Activation and Acetylcholine
Receptor Clustering*
Anke
Watty and
Steven J.
Burden§
From the Molecular Neurobiology Program, Skirball Institute of
Biomolecular Medicine, New York University Medical School, New
York, New York 10016
MuSK, a muscle-specific receptor tyrosine kinase
that is activated by agrin, has a critical role in neuromuscular
synapse formation. In cultured myotubes, agrin stimulates the rapid
phosphorylation of MuSK, leading to MuSK activation and tyrosine
phosphorylation and clustering of acetylcholine receptors. Agrin,
however, fails to stimulate tyrosine phosphorylation of MuSK that is
force-expressed in myoblasts and fibroblasts, indicating that myotubes
contain an additional activity that is required for agrin to stimulate MuSK. Certain glycosyltransferases are expressed selectively at synaptic sites in skeletal muscle, raising the possibility that carbohydrate modifications of MuSK, catalyzed by glycosyltransferases expressed selectively in myotubes, may be essential for agrin to bind
and activate MuSK. We identifed two N-linked glycosylation sites in MuSK, and we expressed MuSK mutants lacking one or both N-linked sites into MuSK mutant myotubes to
determine whether N-linked carbohydrate modifications of
MuSK have a role in MuSK activation. We found that N-linked
glycosylation restrains ligand-independent tyrosine phosphorylation of
MuSK and downstream signaling but is not necessary for agrin to
stimulate MuSK.
*
This work was supported in part by National Institutes of
Health Grant NS36193 (to S. J. B.).The costs of publication of this article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
Supported by a postdoctoral fellowship from the Deutsche
Forschungsgemeinschaft. Present address: Mojave Therapeutics, 19 Bradhurst Ave., Hawthorne, NY 10532.
§
To whom correspondence should be addressed: Skirball Institute of
Biomolecular Medicine, NYU Medical School, 540 First Ave., New York, NY
10016. Tel.: 212-263-7341; Fax: 212-263-2842; E-mail: burden@saturn.med.nyu.edu.
Copyright © 2002 by The American Society for Biochemistry and Molecular Biology, Inc.

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