Localization of the RNA-binding proteins Staufen1 and Staufen2 at the mammalian neuromuscular junction.
Staufen is an RNA-binding protein, first identified for its role in oogenesis and CNS development in Drosophila. Two mammalian homologs of Staufen have been identified and shown to bind double-stranded RNA and tubulin, and to function in the somatodendritic transport of mRNA in neurons. Here, we examined whether Staufen proteins are expressed in skeletal muscle in relation to the neuromuscular junction. Immunofluorescence experiments revealed that Staufen1 (Stau1) and Staufen2 (Stau2) accumulate preferentially within the postsynaptic sarcoplasm of muscle fibers as well as at newly formed ectopic synapses. Western blot analyses showed that the levels of Stau1 and Stau2 are greater in slow muscles than in fast-twitch muscles. Muscle denervation induced a significant increase in the expression of Stau1 and Stau2 in the extrasynaptic compartment of both fast and slow muscles. Consistent with these observations, we also demonstrated that expression of Stau1 and Stau2 is increased during myogenic differentiation and that treatment of myotubes with agrin and neuregulin induces a further increase in the expression of both Staufen proteins. We propose that Stau1 and Stau2 are key components of the postsynaptic apparatus in muscle, and that they contribute to the maturation and plasticity of the neuromuscular junction.
Bélanger
Guy
G
Department of Cellular and Molecular Medicine, and Center for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada.
Stocksley
Mark A
MA
Vandromme
Marie
M
Schaeffer
Laurent
L
Furic
Luc
L
DesGroseillers
Luc
L
Jasmin
Bernard J
BJ
D018171:Agrin / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D051379:Mice; D008810:Mice, Inbred C57BL; D009121:Muscle Denervation; D018656:Muscle Fibers, Fast-Twitch / Q000737:chemistry / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D018657:Muscle Fibers, Slow-Twitch / Q000737:chemistry / Q000378:metabolism; D018482:Muscle, Skeletal / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000096:biosynthesis*; D020880:Neuregulins / Q000494:pharmacology; D009469:Neuromuscular Junction / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000032:analysis / Q000096:biosynthesis*
D018171:Agrin; D009419:Nerve Tissue Proteins; D020880:Neuregulins; D016601:RNA-Binding Proteins; C492187:Stau1 protein, mouse; C471845:stau2 protein, mouse; C117884:staufen protein, mammalian