期刊
FRONTIERS IN CELLULAR NEUROSCIENCE
卷 14, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/fncel.2020.00180
关键词
neuronal polarity; protein compartmentalization; axon initial segment; correlative imaging; super-resolution; fluorescence loss in photobleaching; computational modeling
资金
- Max Planck Society
- European Research Council
- DFG [CRC 902, 1080]
- DFG Cluster of Excellence for Macromolecular Complexes
- Inserm
- Universite de Paris
- NRJ Foundation
- Agence Nationale de la Recherche [ANR-16-CE16-0009-01]
- Agence Nationale de la Recherche (ANR) [ANR-16-CE16-0009] Funding Source: Agence Nationale de la Recherche (ANR)
By limiting protein exchange between the soma and the axon, the axon initial segment (AIS) enables the segregation of specific proteins and hence the differentiation of the somatodendritic compartment and the axonal compartment. Electron microscopy and super-resolution fluorescence imaging have provided important insights in the ultrastructure of the AIS. Yet, the full extent of its filtering properties is not fully delineated. In particular, it is unclear whether and how the AIS opposes the free exchange of soluble proteins. Here we describe a robust framework to combine whole-cell photobleaching and retrospective high-resolution imaging in developing neurons. With this assay, we found that cytoplasmic soluble proteins that are not excluded from the axon upon expression over tens of hours exhibit a strong mobility reduction at the AIS - i.e., are indeed compartmentalized - when monitored over tens of minutes. This form of compartmentalization is developmentally regulated, requires intact F-actin and may be correlated with the composition and ultrastructure of the submembranous spectrin cytoskeleton. Using computational modeling, we provide evidence that both neuronal morphology and the AIS regulate this compartmentalization but act on distinct time scales, with the AIS having a more pronounced effect on fast exchanges. Our results thus suggest that the rate of protein accumulation in the soma may impact to what extent and over which timescales freely moving molecules can be segregated from the axon. This in turn has important implications for our understanding of compartment-specific signaling in neurons.
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