The neuronal protein Neurexin directly interacts with the Scribble–Pix complex to stimulate F-actin assembly for synaptic vesicle clustering

Abstract

Synaptic vesicles (SVs) form distinct pools at synaptic terminals, and this well-regulated separation is necessary for normal neurotransmission. However, how the SV cluster, in particular synaptic compartments, maintains normal neurotransmitter release remains a mystery. The presynaptic protein Neurexin (NRX) plays a significant role in synaptic architecture and function, and some evidence suggests that NRX is associated with neurological disorders, including autism spectrum disorders. However, the role of NRX in SV clustering is unclear. Here, using the neuromuscular junction at the 2–3 instar stages of Drosophila larvae as a model and biochemical imaging and electrophysiology techniques, we demonstrate that Drosophila NRX (DNRX) plays critical roles in regulating synaptic terminal clustering and release of SVs. We found that DNRX controls the terminal clustering and release of SVs by stimulating presynaptic F-actin. Furthermore, our results indicate that DNRX functions through the scaffold protein Scribble and the GEF protein DPix to activate the small GTPase Ras-related C3 Botulinum toxin substrate 1 (Rac1). We observed a direct interaction between the C-terminal PDZ-binding motif of DNRX and the PDZ domains of Scribble and that Scribble bridges DNRX to DPix, forming a DNRX–Scribble–DPix complex that activates Rac1 and subsequently stimulates presynaptic F-actin assembly and SV clustering. Taken together, our work provides important insights into the function of DNRX in regulating SV clustering, which could help inform further research into pathological neurexin-mediated mechanisms in neurological disorders such as autism.

Local adaptation across a complex bioclimatic landscape in two montane bumble bee species

“…In insects generally, loss of neuromuscular function at cold temperatures can lead to the loss of coordinated movement and, ultimately, "chill coma" (Kelty & Lee, 2001;MacMillan & Sinclair, 2011;Overgaard & MacMillan, 2017 Path encoding genes in D. melanogaster (e.g., the LOC100747727-LOC100747447 region with beat-III, LOC100746249 and a second gene LOC100740312 with sidestep genes), which is worth further investigation because these proteins directly interact at the motor neuron synapse (Arzan Zarin & Labrador, 2019;Carrillo et al, 2015;Inaki, Yoshikawa, Thomas, Aburatani, & Nose, 2007;Li et al, 2017;Pipes, Lin, Riley, & Goodman, 2001). Finally, a few more general neural genes also contain outliers in both species, such as the neurexin family loci that plays a role in synapse architecture and function (Menon, Carrillo, & Zinn, 2013;Rui et al, 2017).…”

Choline Transporter in α/β core neurons of Drosophila mushroom body non-canonically regulates pupal eclosion and maintains neuromuscular junction integrity

“…Proteins like Drosophila neurexins (DNRx), Scribble and RanBPM have been shown to be present in MB and are also associated with NMJ phenotype (Rui et al, 2017; Scantlebury et al, 2010). Therefore, we determined if the locomotor defect caused by downregulation of ChT in α/βc neurons could be due to alteration in NMJ morphology.…”

“…The underlying mechanism of how ChT in α/βc neurons affects NMJ morphology is currently unclear. However, like ChT, several other proteins, namely; Drosophila Neurexins, Scribble, adaptor protein DRK and Wallenda have also been reported to have localisation in MB and play a role in maintaining structural plasticity at NMJs via different signalling cascades (Moressis et al, 2009; Rui et al, 2017; Shin and DiAntonio, 2011). Previous reports also describe that MB physiology regulates locomotor activity rhythms in Drosophila (Gorostiza et al, 2014; Mabuchi et al, 2016).…”

The calcium channel subunit α2δ-3 organizes synapses via a novel activity-dependent, autocrine BMP signaling pathway

“…Together, these findings argue that presynaptic, autocrine Gbb signaling regulates SSV distribution. Interestingly, LOF mutations in the conserved synaptic adhesion molecule Neurexin-1 display the same phenotype (Rui et al, 2017), suggesting that large-scale spatial organization of SSVs within boutons could be a common function of synapse organizing pathways.…”