Acetylcholine receptors and concanavalin A-binding sites on cultured Xenopus muscle cells: electrophoresis, diffusion, and aggregation [corrected and republished article originally printed in J Cell Biol 1988 May;106(5):1723-34]

Abstract

Using digitally analyzed fluorescence videomicroscopy, we have examined the behavior of acetylcholine receptors and concanavalin A binding sites in response to externally applied electric fields. The distributions of these molecules on cultured Xenopus myoballs were used to test a simple model which assumes that electrophoresis and diffusion are the only important processes involved. The model describes the distribution of concanavalin A sites quite well over a fourfold range of electric field strengths; the results suggest an average diffusion constant of approximately 2.3 X 10(-9) cm2/s. At higher electric field strengths, the asymmetry seen is substantially less than that predicted by the model. Acetylcholine receptors subjected to electric fields show distributions substantially different from those predicted on the basis of simple electrophoresis and diffusion, and evidence a marked tendency to aggregate. Our results suggest that this aggregation is due to lateral migration of surface acetylcholine receptors, and is dependent on surface interactions, rather than the rearrangement of microfilaments or microtubules. The data are consistent with a diffusion-trap mechanism of receptor aggregation, and suggest that the event triggering receptor localization is a local increase in the concentration of acetylcholine receptors, or the electrophoretic concentration of some other molecular species. These observations suggest that, whatever mechanism(s) trigger initial clustering events in vivo, the accumulation of acetylcholine receptors can be substantially enhanced by passive, diffusion-mediated aggregation.

Local accumulation of acetylcholine receptors is neither necessary nor sufficient to induce cluster formation

“…Using a model system-cultured Xenopus muscle cells exposed to electric fields-we have shown that AChRs, concentrated at the cathode-facing cell pole, continue to aggregate there after the field is terminated (Stollberg and Fraser, 1988). These observations are consistent with the possibility that the field-induced increase in receptor concentration triggers the aggregation event.…”

Controlling Cell Behavior Electrically: Current Views and Future Potential

“…Beginning at the receptor level, a physiological EF physically moves charged receptor molecules exposed on the outer surface of the lipid bilayer and creates receptor asymmetry between cathodal-and anodal-facing membranes (89,163). An applied EF induces receptor asymmetries for the polysaccharide-binding plant lectins such as concanavalin A (conA) and for the neurotransmitter ACh on Xenopus myoblasts and on neurons (156,162,193). The epidermal growth factor (EGF) receptors on corneal epithelial cells (219) and on fibroblasts (73) also are redistributed by a physiological EF (Fig.…”

Neurophysiological basis of a new electrode configuration to potentiate the tDCS: Protocols for upper limbs

“…An important phenomenon induced by the application of direct current is electrolysis, that can alter acidbase balance, generating alkalosis or acidosis, which markedly alters cellular function. Changes in intracellular Ca2+ concentration have also been associated with direct current stimulation [46][47][48][49] . These results demonstrate that although tDCS promotes direct effects on the intrinsic electrical properties and parameters of neurotransmission, it also alters the cellular microenvironment and the molecules that compose it.…”

“…Although the effects of direct current stimulation directly influence the electrical properties of the membrane, alterations in the neuronal microenvironment may also justify the changes induced in its behavior [46][47][48][49][50] . In fact, migration and conformational change of proteins, alteration in tissue pH and incorporation of cholinergic receptors are some of the biological effects promoted by the application of exogenous continuous currents 25 .…”