Aberrant somatic calcium channel function in cNurr1 and LRRK2-G2019S mice

Area of Science:

• Neuroscience
• Neurodegenerative Diseases
• Molecular Biology

Background:

• Parkinson's disease (PD) involves the degeneration of dopaminergic (DA) neurons, with axon loss preceding somatic cell death.
• Calcium influx through voltage-gated calcium channels (VGCCs) is implicated in neuronal function and potential loss.
• The specific roles of T-type and L-type VGCCs in DA neuron somata and axon terminals in PD pathogenesis remain unclear.

Purpose of the Study:

• To investigate the function of T-type and L-type VGCCs in the substantia nigra pars compacta (SNc) DA neurons of two distinct PD mouse models.
• To determine if VGCC dysfunction contributes to neuronal deficits in these PD models.
• To explore the potential impact of oxidative stress and specific inhibitors on VGCC function in PD.

Main Methods:

• Electrophysiological recordings were performed on SNc-DA neurons from adult cNurr1 knockout mice and middle-aged G2019S LRRK2 mutation knock-in mice.
• Intrinsic membrane properties, pacemaker firing, and the contribution of T-type and L-type VGCCs to firing were analyzed.
• Effects of a LRRK2 kinase inhibitor and an antioxidant flavonoid were assessed on VGCC function.

Main Results:

• While overall neuronal properties were largely preserved, L-type VGCCs uniquely contributed to pacemaker firing in G2019S mice.
• T-type VGCC contribution to firing was reduced in cNurr1 mice, alongside desensitized somatic dopamine-D2 autoreceptors.
• Altered VGCC contributions were normalized by the antioxidant flavonoid, suggesting a role for oxidative stress, but not the LRRK2 inhibitor.

Conclusions:

• Opposite alterations in T-type and L-type VGCC function occur in the somata of SNc-DA neurons in different PD models.
• These VGCC changes are linked to oxidative stress and affect neuronal firing, but not dopamine release from axon terminals.
• The findings highlight cell-body-specific VGCC dysregulation as a potential factor in PD pathogenesis, independent of LRRK2 kinase activity.