title: Mercury decreases the frequency of induced but not spontaneous clustering of acetylcholine receptors.
abstract: Studies with environmental levels of various metals typically focus on observable neurological symptoms in newborns and adults. Use of the C2C12 skeletal muscle cell line as a developmental model enabled us to test whether environmental insults prevented myotube formation or the assembly of the postsynaptic component of the neuromuscular synapse. Specifically, we asked whether the inorganic metal mercury interfered with the fusion of myoblasts into myotubes, acetylcholine receptor (AChR) clustering, or the agrin signaling events that precede AChR clustering. C2C12 myotubes grown in culture medium containing 10 microM mercuric chloride were morphologically indistinguishable from control myotubes at the light-microscopic level, and myoblasts fused into myotubes normally. However, myotubes pretreated with mercury demonstrated a decreased frequency of AChR clustering induced by agrin and other experimental manipulations. Furthermore, mercury pretreatment decreased the agrin-induced tyrosine phosphorylation of the AChR beta subunit, thus inhibiting the agrin signal transduction pathway. In contrast, mercury failed to decrease the frequency of spontaneous AChR clustering, suggesting that spontaneous AChR clustering differs from agrin-induced AChR clustering in some significant way.
authors.affiliation: Department of Anatomy, Arizona College of Osteopathic Medicine, Midwestern University, 19555 N. 59th Avenue, Glendale, AZ 85308, USA.
authors.forename: Tyrone J
authors.initials: TJ
authors.lastname: Miller
authors.forename: Wade A
authors.initials: WA
authors.lastname: Grow
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D008628:Mercury / Q000633:toxicity*; D051379:Mice; D018485:Muscle Fibers, Skeletal; D032446:Myoblasts / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011940:Receptor Aggregation / Q000187:drug effects* / Q000502:physiology; D011950:Receptors, Cholinergic / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D011950:Receptors, Cholinergic; D014443:Tyrosine; D008628:Mercury