Department of Functional Neuroanatomy, Institute for Anatomy and Cell Biology, Heidelberg University, Im Neuenheimer Feld 307, 69120, Heidelberg, Germany.
Departments of Functional Genomics and Clinical Genetics, Center for Neurogenomics and Cognitive Research (CNCR), VU University Amsterdam and VU University Medical Center, De Boelelaan, 1087, 1081 HV Amsterdam, The Netherlands.
J Physiol. 2018 Aug;596(16):3759-3773. doi: 10.1113/JP276022. Epub 2018 Jul 1.
Despite their immense physiological and pathophysiological importance, we know very little about the biology of dense core vesicle (DCV) trafficking in the intact mammalian brain. DCVs are transported at similar average speeds in the anaesthetized and awake mouse brain compared to neurons in culture, yet maximal speed and pausing fraction of transport were higher. Microtubule plus (+)-end extension imaging visualized microtubular growth at 0.12 μm/s and revealed that DCVs were transported faster in the anterograde direction. DCV transport slowed down upon presynaptic bouton approach, possibly promoting synaptic localization and cargo release. Our work provides a basis to extrapolate DCV transport properties determined in cultured neurons to the intact mouse brain and reveals novel features such as slowing upon bouton approach and brain state-dependent trafficking directionality.
Neuronal dense core vesicles (DCVs) transport many cargo molecules like neuropeptides and neurotrophins to their release sites in dendrites or axons. The transport properties of DCVs in axons of the intact mammalian brain are unknown. We used viral expression of a DCV cargo reporter (NPY-Venus/Cherry) in the thalamus and two-photon in vivo imaging to visualize axonal DCV trafficking in thalamocortical projections of anaesthetized and awake mice. We found an average speed of 1 μm/s, maximal speeds of up to 5 μm/s and a pausing fraction of ∼11%. Directionality of transport differed between anaesthetized and awake mice. In vivo microtubule +-end extension imaging using MACF18-GFP revealed microtubular growth at 0.12 μm/s and provided positive identification of antero- and retrograde axonal transport. Consistent with previous reports, anterograde transport was faster (∼2.1 μm/s) than retrograde transport (∼1.4 μm/s). In summary, DCVs are transported with faster maximal speeds and lower pausing fraction in vivo compared to previous results obtained in vitro. Finally, we found that DCVs slowed down upon presynaptic bouton approach. We propose that this mechanism promotes synaptic localization and cargo release.
尽管致密核心囊泡 (DCV) 在完整哺乳动物大脑中的运输具有巨大的生理和病理生理学意义，但我们对其生物学知之甚少。与培养的神经元相比，在麻醉和清醒的小鼠大脑中，DCV 的平均运输速度相似，但最大速度和运输暂停分数更高。微管 + (+)-端延伸成像以 0.12 μm/s 的速度可视化微管生长，并显示 DCV 在顺行方向上的运输速度更快。当突触前末梢接近时，DCV 运输速度减慢，可能促进突触定位和货物释放。我们的工作为将在培养神经元中确定的 DCV 运输特性推断到完整的小鼠脑中提供了基础，并揭示了一些新的特征，例如在接近末梢时速度减慢以及大脑状态依赖性运输方向性。
神经元致密核心囊泡 (DCV) 将许多 cargo 分子（如神经肽和神经营养因子）运输到其在树突或轴突中的释放部位。完整哺乳动物大脑中轴突中 DCV 的运输特性尚不清楚。我们使用病毒表达 DCV 货物报告基因（NPY-Venus/Cherry）在丘脑中，并使用双光子在体成像来可视化麻醉和清醒小鼠丘脑皮质投射中的轴突 DCV 运输。我们发现平均速度为 1 μm/s，最大速度高达 5 μm/s，暂停分数约为 11%。在麻醉和清醒小鼠之间，运输的方向性不同。使用 MACF18-GFP 的体内微管 +-端延伸成像显示微管生长速度为 0.12 μm/s，并提供了顺行和逆行轴突运输的阳性鉴定。与之前的报道一致，顺行运输速度（2.1 μm/s）快于逆行运输速度（1.4 μm/s）。总的来说，与之前在体外获得的结果相比，体内 DCV 的最大速度更快，暂停分数更低。最后，我们发现 DCV 在接近突触前末梢时速度减慢。我们提出，这种机制促进了突触定位和货物释放。
