Substance P plays an important role in cell adhesion molecule 1-mediated nerve–pancreatic islet α cell interaction

Decreased intracellular granule movement and glucagon secretion in pancreatic α cells attached to superior cervical ganglion neurites

Autonomic neurons innervate pancreatic islets of Langerhans and participate in the maintenance of blood glucose concentrations by controlling hormone levels through attachment with islet cells. We previously found that stimulated superior cervical ganglia (SCG) could induce Ca²⁺ oscillation in α cells via neuropeptide substance P using an in vitro co-culture model. In this study, we studied the effect of SCG neurite adhesion on intracellular secretory granule movement and glucagon secretion in α cells stimulated by low glucose concentration. Spinning disk microscopic analysis revealed that the mean velocity of intracellular granules was significantly lower in α cells attached to SCG neurites than that in those without neurites under low (2 mM), middle (10 mM), and high (20 mM) glucose concentrations. Stimulation by a low (2 mM) glucose concentration significantly increased glucagon secretion in α cells lacking neurites but not in those bound to neurites. These results suggest that adhesion to SCG neurites decreases low glucose-induced glucagon secretion in pancreatic α cells by attenuating intracellular granule movement activity.

Bidirectional communication between sensory neurons and osteoblasts in an in vitro coculture system

Recent studies have revealed that the sensory nervous system is involved in bone metabolism. However, the mechanism of communication between neurons and osteoblasts is yet to be elucidated. In this study, we investigated the signaling pathways between sensory neurons of the dorsal root ganglion (DRG) and the osteoblast-like MC3T3-E1 cells using an in vitro coculture system. Our findings indicate that signal transduction from DRG-derived neurons to MC3T3-E1 cells is suppressed by antagonists of the AMPA receptor and the NK₁ receptor. Conversely, signal transduction from MC3T3-E1 cells to DRG-derived neurons is suppressed by a P2X₇ receptor antagonist. Our results suggest that these cells communicate with each other by exocytosis of glutamate, substance P in the efferent signal, and ATP in the afferent signal.

Fine tuning the LightOn light-switchable transgene expression system

Spatiotemporal control of transgene expression in living cells provides new opportunities for the characterization of gene function in complex biological processes. We previously reported a synthetic, light-switchable transgene expression system called LightOn that can be used to control gene expression using blue light. In the present study, we modified the different promoter segments of the light switchable transcription factor GAVPO and the target gene, and assayed their effects on protein expression under dark or light conditions. The results showed that the LightOn system maintained its high on/off ratio under most modifications, but its induction efficiency and background gene expression level can be fine-tuned by modifying the core promoter, the UASG sequence number, the length of the spacer between UASG and the core promoter of the target protein, and the expression level of the GAVPO transcription factor. Thus, the LightOn gene expression system can be adapted to a large range of applications according to the requirements of the background and the induced gene expression.