PT  - JOURNAL ARTICLE
AU  - E Lasser-Katz
AU  - A Simchovitz
AU  - W-H Chiu
AU  - WH Oertel
AU  - R Sharon
AU  - H Soreq
AU  - J Roeper
AU  - JA Goldberg
TI  - Mutant α-Synuclein overexpression induces stressless pacemaking in vagal motoneurons at risk in Parkinson's disease
AID  - 10.1523/JNEUROSCI.1079-16.2016
DP  - 2016 Nov 09
TA  - The Journal of Neuroscience
PG  - 1079-16
4099  - http://www.jneurosci.org/content/early/2016/11/09/JNEUROSCI.1079-16.2016.short
4100  - http://www.jneurosci.org/content/early/2016/11/09/JNEUROSCI.1079-16.2016.full
AB  - α-Synuclein overexpression (ASOX) drives the formation of toxic aggregates in neurons that are vulnerable in Parkinson disease (PD), including dopaminergic neurons of the substantia nigra (SN) and cholinergic neurons of the dorsal motor nucleus of the vagus (DMV). Just as these populations differ in when they exhibit α-Synucleinopathies during PD pathogenesis, they could also differ in their physiological responses to ASOX. An ASOX-mediated hyperactivity of SN dopamine neurons, which was caused by oxidative dysfunction of Kv4.3 potassium channels, was recently identified in transgenic (A53T-SNCA) mice overexpressing mutated human α-Synuclein. As DMV neurons display extensive α-Synucleinopathies earlier than SN dopamine neurons while exhibiting milder cell loss in PD, we aimed to define their electrophysiological properties in A53T-SNCA mice. We found that DMV neurons maintain normal firing rates in response to ASOX. Moreover, Kv4.3 channels in DMV neurons exhibited no oxidative dysfunction in the A53T-SNCA mice, which could only be recapitulated in wild type mice by glutathione dialysis. Two-photon imaging of redox-sensitive GFP corroborated that mitochondrial oxidative stress was diminished in DMV neurons in the A53T-SNCA mice. This reduction in oxidative stress resulted from a transcriptional downregulation of voltage-activated (Cav) calcium channels in DMV neurons, which lead to a reduction in activity-dependent calcium influx via Cav channels. Thus, ASOX induces a homeostatic remodeling with improved redox signaling in DMV neurons that could explain the differential vulnerability of SN dopamine and DMV neurons in PD and could promote neuroprotective strategies that emulate endogenous homeostatic responses to ASOX (e.g., stressless pacemaking) in DMV neurons.SIGNIFICANCE STATEMENTOverexpression of mutant α-Synuclein causes Parkinson's disease, presumably by driving neurodegeneration in vulnerable neuronal target populations. However, the extent of α-Synuclein pathology (e.g. Lewy bodies) is not directly related to the degree of neurodegeneration across various vulnerable neuronal populations. Here, we show that — in contrast to dopamine neurons in the substantia nigra — vagal motoneurons do not enhance their excitability and oxidative load in response to chronic mutant α-Synuclein overexpression. Rather, by down-regulating their voltage-activated calcium channels they acquire a stressless form of pacemaking, which diminishes mitochondrial and cytosolic oxidative stress. Emulating this endogenous adaptive response to α-Synuclein overexpression could lead to novel strategies to protect dopamine neurons and perhaps delay the onset of Parkinson's disease.