Neurexin–Neuroligin 1 regulates synaptic morphology and functions via the WAVE regulatory complex in Drosophila neuromuscular junction

Abstract

Neuroligins are postsynaptic adhesion molecules that are essential for postsynaptic specialization and synaptic function. But the underlying molecular mechanisms of neuroligin functions remain unclear. We found that Drosophila Neuroligin 1 (DNlg1) regulates synaptic structure and function through WAVE regulatory complex (WRC)-mediated postsynaptic actin reorganization. The disruption of DNlg1, DNlg2, or their presynaptic partner neurexin (DNrx) led to a dramatic decrease in the amount of F-actin. Further study showed that DNlg1, but not DNlg2 or DNlg3, directly interacts with the WRC via its C-terminal interacting receptor sequence. That interaction is required to recruit WRC to the postsynaptic membrane to promote F-actin assembly. Furthermore, the interaction between DNlg1 and the WRC is essential for DNlg1 to rescue the morphological and electrophysiological defects in dnlg1 mutants. Our results reveal a novel mechanism by which the DNrx-DNlg1 trans-synaptic interaction coordinates structural and functional properties at the neuromuscular junction.

Neurexin and Neuroligins Maintain the Balance of Ghost and Satellite Boutons at the Drosophila Neuromuscular Junction

“…We did not observe satellite boutons in the dnlg2 (Figure 7A) mutants or rescued 24B-Gal4;UAS-dnlg3 ( Figure 7B) and dnlg3 (Figures 7C,C ) mutants as reported by Sun et al (2011) and Xing et al (2018). However, we frequently observed typical satellite boutons in the dnlg2;dnlg3 double mutant ( Figures 7D,E and Table 1).…”

“…The dbrat 11 and dbrat 192 strains were obtained from Dr. Zhang and were previously shown to carry a recessive lethal partial deletion of the dbrat gene (Shi et al, 2013). The following fly mutants were used: dnrx 273 (Li et al, 2007), dnlg1 ex1.9 and dnlg1 ex2.3 (Banovic et al, 2010), dnlg2 KO70 and dnlg3 KO127 (Xing et al, 2018), and dnlg4 KO10 (Zhang et al, 2017). The following w 1118 overexpression strains were used: 24B-Gal4;UAS-dnlg1, 24B-Gal4;UAS-dnlg2, MHC-Gal4;UAS-dnlg3 (Xing et al, 2014), and Ok6-Gal4;UAS-dnlg4 (Zhang et al, 2017), as well as dnlg2 KO70 ;dnlg3 KO127 , Ok6-Gal4;UAS-dnrx, and MHC-Gal4;UAS-dnlg1, which were generated in our laboratory.…”

“…Dissection and fixation were based on standard procedures (Xing et al, 2018). In brief, the wandering late third-instar larvae were dissected with standard techniques in Jan solution (128 mM NaCl, 2 mM KCl, 4 mM MgCl 2 , 35 mM sucrose, 5 mM HEPES, pH 7.4) and fixed at 4 • C overnight in a mixture of 2% glutaraldehyde and 2% formaldehyde in 0.1 M sodium cacodylate buffer (pH 7.4), followed by several rinses with cacodylate buffer.…”

Synapse development and maturation at the drosophila neuromuscular junction

“…Loss of either Neurexins or Neuroligins results in severe, or even lethal, defects in synapse formation and function in multiple systems [88][89][90][91][92], reflecting their central role in promoting the formation of stable junctions between pre-and postsynaptic components across organisms [88,[93][94][95][96][97][98]. Work at the Drosophila NMJ indicates that the postsynaptic targets of Nrx-1-Nlg1 include neurotransmitter receptors [93] and the WAVE regulatory complex, which modulates actin cytoskeletal dynamics [99]; downstream presynaptic targets of Nrx-1-Nlg1 include core AZ components [93] and BMP pathway receptors and effectors [94]. Further evidence for the bidirectional nature of Nrx-1-Nlg1 complex-mediated interactions include the finding that the presynaptic AZ component Syd-1 binds Nrx-1 directly to act via Nrx-1-Nlg1 to regulate GluRs composition and clustering [93]; this illustrates one mechanism by which the core AZ machinery can organize their postsynaptic counterparts.…”

Neurexin and Neuroligins Jointly Regulate Synaptic Degeneration at the Drosophila Neuromuscular Junction based on TEM Studies

“…However, there was obvious synaptic degeneration in the dnlg2;dnlg3 and dnrx 83 /dnlg2 double mutants, which further con rms that there is a synergistic function between dnrx and dnlgs and between dnlg2 and dnlg3. dnrx and dnlgs mutation interfered with the BMP and Wnt signaling pathways by disrupting spectin [59], actin [58], and microtubules [60], all of which are essential cytoskeleton components necessary for synapse formation and development. Mutations in members of the BMP pathway, such as wit and gbb [50,61], have been shown to cause abnormal presynaptic ru es that were similar to those observed in dnrx and dnlgs mutants [40,43,60] and caused presynaptic shedding of T-bars [50], similar to that observed in dnrx 273 mutants (Fig.…”