Dorsal root ganglion axon bifurcation tolerates increased cyclic GMP levels: the role of phosphodiesterase 2A and scavenger receptor Npr3
Dorsal root ganglion axon bifurcation tolerates increased cyclic GMP levels: the role of phosphodiesterase 2A and scavenger receptor Npr3
复制标题
DOI：
10.1111/ejn.13434
复制
发表时间：
2016-11
影响因子：
3.4
通讯作者：
H. Schmidt;Stefanie Peters;Katharina Frank;Lai Wen;R. Feil;F. Rathjen
中科院分区：
文献类型：
--
作者：
H. Schmidt;Stefanie Peters;Katharina Frank;Lai Wen;R. Feil;F. Rathjen
环鸟苷酸 (cGMP) 信号通路由 C 型利钠肽 (CNP)、其鸟苷酸环化酶受体 Npr2 和 cGMP 依赖性蛋白激酶 I 组成，在分别进入小鼠脊髓和后脑时，对于背根神经节 (DRG) 和颅感觉神经节轴突的分叉至关重要。然而，在 DRG 神经元中降解 cGMP 的磷酸二酯酶 (PDE) 的身份和功能相关性尚不完全清楚。在这里，我们询问 PDE 对细胞内 cGMP 浓度的调节是否会调节感觉轴突的分支。使用基因编码的荧光 cGMP 传感器对 cGMP 进行实时成像、RT-PCR 筛选、原位杂交和免疫组织学结合突变小鼠的分析，确定 PDE2A 是胚胎 DRG 神经元中 CNP 诱导的 cGMP 降解的主要酶。对 PDE2A 缺陷的 DRG 感觉轴突的追踪与 cGMP 测量结果表明，轴突分叉可以耐受 cGMP 浓度的增加。由于我们发现利钠肽清道夫受体 Npr3 在早期发育阶段由与背根相关的细胞表达，但在 DRG 神经元本身中不表达，因此我们分析了 Npr3 缺失情况下的轴突分支。在 Npr3 缺陷小鼠中，大多数感觉轴突表现出正常分叉，但少数轴突（13%）无法形成 T 状分支，仅在头侧或尾侧方向产生转弯。综上所述，这项研究表明感觉轴突分叉对 CNP 诱导的 cGMP 水平的增加不敏感，并且 Npr3 在该轴突系统中不具有重要的清除功能。
A cyclic GMP (cGMP) signaling pathway, comprising C‐type natriuretic peptide (CNP), its guanylate cyclase receptor Npr2, and cGMP‐dependent protein kinase I, is critical for the bifurcation of dorsal root ganglion (DRG) and cranial sensory ganglion axons when entering the mouse spinal cord and the hindbrain respectively. However, the identity and functional relevance of phosphodiesterases (PDEs) that degrade cGMP in DRG neurons are not completely understood. Here, we asked whether regulation of the intracellular cGMP concentration by PDEs modulates the branching of sensory axons. Real‐time imaging of cGMP with a genetically encoded fluorescent cGMP sensor, RT‐PCR screens, in situ hybridization, and immunohistology combined with the analysis of mutant mice identified PDE2A as the major enzyme for the degradation of CNP‐induced cGMP in embryonic DRG neurons. Tracking of PDE2A‐deficient DRG sensory axons in conjunction with cGMP measurements indicated that axon bifurcation tolerates increased cGMP concentrations. As we found that the natriuretic peptide scavenger receptor Npr3 is expressed by cells associated with dorsal roots but not in DRG neurons itself at early developmental stages, we analyzed axonal branching in the absence of Npr3. In Npr3‐deficient mice, the majority of sensory axons showed normal bifurcation, but a small population of axons (13%) was unable to form T‐like branches and generated turns in rostral or caudal directions only. Taken together, this study shows that sensory axon bifurcation is insensitive to increases of CNP‐induced cGMP levels and Npr3 does not have an important scavenging function in this axonal system.