Localization of intracellular proteins at acetylcholine receptor clusters induced by electric fields in Xenopus muscle cells

Abstract

Electric fields cause acetylcholine receptor (AChR) patches to form on the cathodal sides of cultured muscle cells. These patches are stable for several hours following cessation of an electric field treatment, indicating that the receptors are anchored to the cluster sites. Furthermore, at the ultrastructural level, AChR patches induced by electric fields are marked by an accumulation of extracellular matrix material and a sarcolemmal density. Thus, these AChR patches are similar to those induced by other stimuli, including nerve, polycation-coated beads, and the tissue culture substratum. Proteins that may be involved in anchoring AChRs have been colocalized with AChR patches induced by the latter three stimuli, but not at AChR patches induced by electric fields. In this study, we demonstrate that three putative anchoring proteins, 43K (K = 10(3) Mr) protein, 58K protein and talin, are associated with field-induced AChR patches. We also show that these proteins persist at field-induced AChR patches following removal of the field, indicating that they are stabilized at the AChR patch. Our data are consistent with the possibility that these proteins contribute to the stabilization of AChRs at patches induced by the electric field. Since 43K, 58K and talin are intracellular proteins, and therefore could not undergo field-induced lateral electrophoresis, our observations support the notion that the electric field triggers the formation of an AChR-stabilizing specialization.