Abstract Details

Title Inhibiting the Depalmitoylase APT1 Protects Against Alpha-synuclein Neurotoxicity: A Novel Target for Disease-modifying Therapy in Human Synucleinopathies

Topic Movement Disorders

Presentation(s) P4 - Poster Session 4 (5:30 PM-6:30 PM)

Poster/Presentation
Number 3-004

Objective We asked whether modulating the fundamental process of protein palmitoylation by targeting depalmitoylase enzymes benefits α-synuclein (αS)-dependent vesicle trafficking defects and cytotoxicity.

Background

Identifying neuroprotection for Parkinson disease (PD) and other synucleinopathies is hampered by limited knowledge of their molecular pathogenesis. αS-induced vesicle trafficking defects (e.g., synaptic vesicle exocytosis) likely play a key role. Palmitoylation, post-translational addition of the fatty acid palmitate to cysteines, regulates trafficking by anchoring specific proteins to vesicle membranes. αS itself is not palmitoylated, but dynamically binds membranes. We hypothesized that abnormal αS membrane-binding impairs trafficking by disrupting palmitoylation of other vesicle proteins. We asked whether modulating palmitoylation by inhibiting acyl-protein-thioesterase-1 (APT1), a key depalmitoylase, could rescue these phenotypes, and if so, via which substrate(s).

Design/Methods Our lab previously found that “amplifying” the αS E46K familial PD mutation by inserting homologous E-to-K mutations in two adjacent KTKEGV repeats (E35K+E46K+E61K = “3K”) causes neurotoxicity and αS-rich cytoplasmic inclusions. We expressed YFP-tagged-3K-αS in neural cells and quantified resultant inclusions. Induced human neurons were differentiated from iPSCs by neurogenin-2. Cytotoxicity was assessed by LDH release.

Results By EM, inclusions are clusters of 3K-αS plus many membrane vesicles indicative of disrupted trafficking. Pharmacologically inhibiting APT1 with ML348 or genetically decreasing it by dsiRNA reduced inclusions in M17D neuroblastoma cells and rat neurons. ML348 restored cell growth and an ATP deficit of the 3K cells. In human neurons, inhibiting APT1 decreased phospho-Ser129-αS (a marker of pathological αS) and neurotoxicity caused by αS viral transduction. Expression of MAP6, an APT1 substrate with microtubule- and vesicle-binding properties, overcame the effects of APT1 inhibition on inclusions in a manner dependent on MAP6 palmitoylation.

Conclusions Our findings support the hypothesis that inhibiting APT1 ameliorates αS-dependent neuropathology through actions on its substrate, the vesicle- and microtubule-binding protein MAP6. Thus, modulating palmitoylation represents an entirely novel approach for synucleinopathy drug development.

Authors/Disclosures
Gary Ho, MD, PhD (Brigham and Women's Hospital, Hale Building) PRESENTER	The institution of Dr. Ho has received research support from American Parkinson Disease Association. The institution of Dr. Ho has received research support from NINDS.
	No disclosure on file
	No disclosure on file
	No disclosure on file
	No disclosure on file
Dennis J. Selkoe, MD, F�鶹��ýӳ�� (Brigham and Women's Hospital)	Dr. Selkoe has received personal compensation in the range of $50,000-$99,999 for serving as a Consultant for Prothena Biosciences. Dr. Selkoe has received personal compensation in the range of $500-$4,999 for serving as a Consultant for EISAI.

�鶹��ýӳ��

�鶹��ýӳ��