Journal of Neuroscience, Vol 3, 2670-2680, Copyright © 1983 by Society for Neuroscience
Acetylcholine receptor clustering in rat myotubes: requirement for CA2+ and effects of drugs which depolymerize microtubules
RJ Bloch
The acetylcholine receptor (AChR) clusters which form in the plasma
membranes of cultured rat myotubes disappear when the myotubes are exposed
to medium depleted of Ca2+. This loss of receptor clusters is reversible
and depends both on extracellular Ca2+ concentrations and on temperature.
Other divalent cations (Mg2+, Ba2+, Sr2+, Co2+, Mn2+) do not maintain
receptor clusters when Ca2+ is absent. Extracellular Na+, which promotes
Ca2+ efflux from myotube cultures, is necessary for cluster loss to occur
in Ca2+-depleted medium. Experiments using colchicine and other drugs which
depolymerize microtubules suggest that the cytoskeleton is involved in AChR
clustering. At submicromolar concentrations, these drugs afford partial
protection against cluster loss caused by Ca2+ depletion. Colchicine also
alters the organization of vinculin in the vicinity of AChR clusters. It is
concluded that receptor clustering probably depends on intracellular Ca2+
and on a structure or mechanism indirectly affected by colchicine.