Neto-α Controls Synapse Organization and Homeostasis at the Drosophila Neuromuscular Junction

Highlights

• Neto-α functions in both pre- and postsynaptic compartments at the Drosophila NMJ

• Postsynaptic Neto-α limits the size of the postsynaptic density

• Presynaptic Neto-α in conjunction with KaiRID regulates basal neurotransmission

• Neto-α enables presynaptic homeostasis via its intracellular domain

Summary

Glutamate receptor auxiliary proteins control receptor distribution and function, ultimately controlling synapse assembly, maturation, and plasticity. At the Drosophila neuromuscular junction (NMJ), a synapse with both pre- and postsynaptic kainate-type glutamate receptors (KARs), we show that the auxiliary protein Neto evolved functionally distinct isoforms to modulate synapse development and homeostasis. Using genetics, cell biology, and electrophysiology, we demonstrate that Neto-α functions on both sides of the NMJ. In muscle, Neto-α limits the size of the postsynaptic receptor field. In motor neurons (MNs), Neto-α controls neurotransmitter release in a KAR-dependent manner. In addition, Neto-α is both required and sufficient for the presynaptic increase in neurotransmitter release in response to reduced postsynaptic sensitivity. This KAR-independent function of Neto-α is involved in activity-induced cytomatrix remodeling. We propose that Drosophila ensures NMJ functionality by acquiring two Neto isoforms with differential expression patterns and activities.