Phosphorylation of Doc2 by EphB2 modulates Munc13-mediated SNARE complex assembly and neurotransmitter release.

At the synapse, presynaptic neurotransmitter release is tightly controlled by release machinery, involving the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins and Munc13. The Ca2+ sensor Doc2 cooperates with Munc13 to regulate neurotransmitter release, but the underlying mechanisms remain unclear. In our study, we have characterized the binding mode between Doc2 and Munc13 and found that Doc2 originally occludes Munc13 to inhibit SNARE complex assembly. Moreover, our investigation unveiled that EphB2, a presynaptic adhesion molecule (SAM) with inherent tyrosine kinase functionality, exhibits the capacity to phosphorylate Doc2. This phosphorylation attenuates Doc2 block on Munc13 to promote SNARE complex assembly, which functionally induces spontaneous release and synaptic augmentation. Consistently, application of a Doc2 peptide that interrupts Doc2-Munc13 interplay impairs excitatory synaptic transmission and leads to dysfunction in spatial learning and memory. These data provide evidence that SAMs modulate neurotransmitter release by controlling SNARE complex assembly.

Cell-cell and cell-matrix adhesion regulated by Piezo1 is critical for stiffness-dependent DRG neuron aggregation.

The dorsal root ganglion (DRG) is characterized by the dense clustering of primary sensory neuron bodies, with their axons extending to target tissues for sensory perception. The close physical proximity of DRG neurons facilitates the integration and amplification of somatosensation, ensuring normal physiological functioning. However, the mechanism underlying DRG neuron aggregation was unclear. In our study, we culture DRG neurons from newborn rats on substrates with varying stiffness and observe that the aggregation of DRG neurons is influenced by mechanical signals arising from substrate stiffness. Moreover, we identify Piezo1 as the mechanosensor responsible for DRG neurons' ability to sense different substrate stiffness. We further demonstrate that the Piezo1-calpain-integrin-ß1/E-cadherin signaling cascade regulates the aggregation of DRG neurons. These findings deepen our understanding of the mechanisms involved in histogenesis and potential disease development, as mechanical signals arising from substrate stiffness play a crucial role in these processes.