Park, J.Y., Ikeda, H., Ikenaga, T., and Ono, F. (2012) Acetylcholine receptors enable the transport of rapsyn from the Golgi complex to the plasma membrane. The Journal of neuroscience : the official journal of the Society for Neuroscience. 32(21):7356-7363.
The accumulation of acetylcholine receptors (AChRs) at nerve terminals is critical for signal transmission at the neuromuscular
junction, and rapsyn is essential for this process. Previous studies suggest that AChRs might direct rapsyn self-clusters
to the synapse. In vivo experiments with fluorescently tagged AChR or rapsyn in zebrafish larvae revealed that rapsyn self-clusters separate from
AChRs did not exist before synapse formation. Examination of rapsyn in the AChR-less mutant sofa potato revealed that rapsyn in the absence of AChR was localized in the Golgi complex. Expression of muscle-type AChR in sofa potato restored synaptic clustering of rapsyn, while neuronal type AChR had no effect. To determine whether this requirement of
protein interaction is reciprocal, we examined the mutant twitch once, which has a missense mutation in rapsyn. While the AChRs distributed nonsynaptically on the plasma membrane in twitch once, mutant rapsyn was retained in the Golgi complex. We conclude that AChRs enable the transport of rapsyn from the Golgi complex
to the plasma membrane through a molecule-specific interaction.