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Table 1 Studies and findings on the uptake and release of a-Syn by neurons, glia, and brain barrier cell types

From: Brain disposition of α-Synuclein: roles of brain barrier systems and implications for Parkinson’s disease

Cell type

a-Syn transport

References

Blood–brain barrier (BBB)

1) Astrocytes: Endogenously expresses a-Syn. Astrocytes take up a-Syn by endocytosis; inflammatory activation occurs upon uptake of a-Syn aggregates. Astrocytes also secrete free a-Syn.

Braak et al., 2007 [3]

2) Endothelia: endothelia of cerebral blood vessels express a-Syn endogenously. No detectable expression of a-Syn was found in BBB endothelia.

Kim et al., 2008 [23]

3) Perictyes: Unknown

Lee et al., 2010a [35]

4) Basal Lamina: Unknown

Lee et al., 2010b [36]

Kim et al., 2013 [37]

Tamo et al., 2002 [38]

Blood-CSF barrier (BCSFB)

Choroid Epithelia: Immortalized Z310 cells express a-Syn endogenously. Z310 cells uptake free a-Syn; clathrin is upregulated during a-Syn exposure. Primary CP epithelia from rat express a-Syn endogenously and take up free a-Syn.

Bates et al., 2012 [46]

Bates et al., 2013 [49]

Neurons

Neurons are capable of both the uptake and secretion of a-Syn. Free and aggregated a-Syn can be secreted and taken up by neurons. Cell-to-cell transmission can occur between neurons or with multiple glial types (e.g. astrocytes, microglia, etc.)

Lee et al., 2005 [15]

Lee et al., 2013 [17

Desplats et al., 2009 [28]

Lee et al., 2008a [30]

Freeman et al., 2013 [31

Büchel et al., 2013 [32]

Glia (excl. astrocytes)

1) Microglia: Microglia take up free and toxic a-Syn aggregates from interstitial fluid. Inflammatory activation upon uptake of a-Syn.

Wakabayashi et al., 2000 [33]

2) Oligodendrocytes: Uptake of aggregated a-Syn was shown to be clathrin-dependent. Consequently, intracellular inclusions containing a-Syn can occur

Kisos et al., 2012 [55]

Lee et al., 2008b [56]