Vision Program, Ottawa Hospital Research Institute, 501 Smyth Road, Ottawa, Ontario, Canada.
Mol Cell Neurosci. 2011 Mar;46(3):583-96. doi: 10.1016/j.mcn.2010.12.009. Epub 2010 Dec 21.
Neurons are an important source of the secreted morphogen Sonic hedgehog (Shh), however, little is known about neuron-specific regulation of Shh transport and secretion. To study this process, we investigated the subcellular distribution of Shh in primary neurons and differentiated cells of a neuroendocrine cell line by fluorescence microscopy and biochemical fractionation. In retinal ganglion cells, endogenous Shh was distributed as intra- and extracellular puncta at the soma, dendrites, axons and neurite terminals. Shh(+) puncta move bidirectionally and colocalize with markers of synaptic vesicles (SVs) and dense core granules. Lipid modification and proteolysis were required for Shh sorting to SVs and cell surface association. Finally, consistent with its association with regulated secretory vesicles, Shh secretion could be induced under depolarizing conditions. Taken together, these observations suggest that long-range Shh transport and signalling in neurons involves trafficking to the regulated secretory pathway and cell surface accumulation of Shh on axons and suggests a link between neuronal activity and Shh release.
神经元是分泌形态发生素 Sonic hedgehog（Shh）的重要来源，然而，神经元特异性调节 Shh 转运和分泌的机制知之甚少。为了研究这一过程，我们通过荧光显微镜和生化分级分离法研究了原代神经元和神经内分泌细胞系分化细胞中 Shh 的亚细胞分布。在视网膜神经节细胞中，内源性 Shh 分布在胞体、树突、轴突和神经末梢的细胞内和细胞外斑点中。Shh(+)斑点可双向移动，并与突触小泡 (SVs) 和致密核心颗粒的标志物共定位。脂质修饰和蛋白水解对于 Shh 向 SVs 和细胞表面的分选是必需的。最后，与它与受调控的分泌小泡的关联一致，Shh 的分泌可以在去极化条件下被诱导。综上所述，这些观察结果表明，神经元中长距离 Shh 转运和信号转导涉及到调节分泌途径的运输以及 Shh 在轴突上的细胞表面积累，并提示神经元活动与 Shh 释放之间存在联系。
