- Four different subunits are essential for expressing the synaptic glutamate receptor at neuromuscular junctions of Drosophila. Qin, G., Schwarz, T., Kittel, R.J., Schmid, A., Rasse, T.M., Kappei, D., Ponimaskin, E., Heckmann, M., Sigrist, S.J. J. Neurosci. (2005)