September 29, 2021

Increasing palmitoylation to rescue estrogen receptor alpha-dependent synaptic deficits in 3K alpha-synuclein mice

Tim Moors, PhD

Additional Authors: Pascal Bechade, Thomas McCaffery, Maria Ericsson, Shaomin Li, Gary Ho, Silke Nuber1

Aims
Women are less vulnerable to neurodegenerative aspects of PD. We previously reported preserved alpha-synuclein (aSyn) homeostasis and reduced dopaminergic loss in female E46K-amplified (3K) aSyn transgenic mice, while estrogen treatment alleviated aSyn pathology and motor phenotypes in male 3K mice. Here, we study the underlying protective effects of estrogen receptor alpha (ERa) and impact of inhibiting the enzyme removing its membrane-stabilizing palmitoyl-tag in physiologically low 3K aSyn-expressing (3KL) mice.

Methods
Cognitive and motor performances were tested in various behavioral paradigms. We applied immunohistochemistry, (super-resolution) microscopy and immuno-EM to assess (sub)cellular localization and histopathology of aSyn and other proteins, quantitative WB/ELISA to study protein levels and biochemical distribution, and electrophysiology on hippocampal tissue slices to analyze synaptic plasticity. Estrogen receptor palmitoylation was measured using Acyl-Biotin Exchange assays.

Results
3KL female mice showed delayed onset of cognitive and motor symptoms, improved aSyn homeostasis (e.g. increased solubility/multimerization) and reduced Ser129-p aSyn cytopathology. Crowding of aSyn at vesicles was associated with impaired synaptic plasticity in 3KL males. Synaptic function was restored after estrogen treatment, which was blocked by ERa antagonists. In 3KL mice, ERa co-clustered at perinuclear and synaptic aSyn accumulations (as in the PD brain), which was associated with decreased ERa palmitoylation. We hence pharmacologically increased ERa palmitoylation using ML-348 (an APT-1 inhibitor) for 80 days, which improved synaptic plasticity and cognitive performances in 3KL (female and male) mice.

Conclusions
Increased synaptic ERa by female sex or ML-348-dependent palmitoylation preserves synaptic plasticity and aids phenotypes downstream the disturbed aSyn homeostasis in a 3KL aSyn PD mouse model.

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