PDF(Pubmed)
Abstract：
Endocannabinoid signalling mediated by cannabinoid receptor 1 (CB1R, also known as CNR1) is critical for homeostatic neuromodulation of both excitatory and inhibitory synapses. This requires highly polarised axonal surface expression of CB1R, but how this is achieved remains unclear. We previously reported that the α-helical H9 domain in the intracellular C terminus of CB1R contributes to axonal surface expression by an unknown mechanism. Here, we show in rat primary neuronal cultures that the H9 domain binds to the endocytic adaptor protein SGIP1 to promote CB1R expression in the axonal membrane. Overexpression of SGIP1 increases CB1R axonal surface localisation but has no effect on CB1R lacking the H9 domain (CB1RΔH9). Conversely, SGIP1 knockdown reduces axonal surface expression of CB1R but does not affect CB1RΔH9. Furthermore, SGIP1 knockdown diminishes CB1R-mediated inhibition of presynaptic Ca2+ influx in response to neuronal activity. Taken together, these data advance mechanistic understanding of endocannabinoid signalling by demonstrating that SGIP1 interaction with the H9 domain underpins axonal CB1R surface expression to regulate presynaptic responsiveness.
摘要：
大麻素受体1（CB1R，也称为CNR1）对于兴奋性和抑制性突触的稳态神经调节至关重要。这需要CB1R的高度极化轴突表面表达，但这是如何实现的还不清楚。我们先前报道了CB1R细胞内C末端的α-螺旋H9结构域通过未知机制促进轴突表面表达。这里,我们在大鼠原代神经元培养物中显示，H9结构域与内吞衔接蛋白SGIP1结合，以促进CB1R在轴突膜中的表达。SGIP1的过表达会增加CB1R轴突表面定位，但对缺少H9结构域的CB1R（CB1RΔH9）没有影响。相反，SGIP1敲低降低CB1R的轴突表面表达，但不影响CB1RΔH9。此外，SGIP1敲低减少CB1R介导的响应于神经元活性的突触前Ca2+内流的抑制。一起来看,这些数据通过证明SGIP1与H9结构域的相互作用支持轴突CB1R表面表达来调节突触前反应性,从而促进了对内源性大麻素信号传导的机制理解.
