Ménage à Trio during BMP-Mediated Retrograde Signaling at the NMJ

Abstract

In flies, retrograde BMP signaling is an important mechanism by which postsynaptic cells regulate the structure and function of presynaptic terminals, ostensibly through changes in gene expression. Transcriptional targets, however, have remained mysterious. In this issue of Neuron, Haghighi and colleagues begin to unravel this puzzle by identifying the cytoskeletal regulator Trio.

Figure 1. Retrograde BMP Signaling at the Drosophila Larval NMJ

Gbb is released by muscle cells, promoting the dimerization of presynaptic Wit and Tkv or Sax. The receptor then phosphorylates Mad within the motor neuron, which establish a complex with Medea. The P-Mad/Medea complex is translocated into the motor neuron nucleus, where it binds to target genes. One such target gene is the GEF Trio, a regulator of Rac, which is thought to regulate the synaptic cytoskeleton, promoting synaptic growth (see text for further details). μT, microtubule; glu, glutamate; GluR, glutamate receptor.