New insights into the role of a-synuclein in the regulation of lipid metabolism and signaling pathways in neurons

CONDE, M.; ALZA, N.P.; SANCHEZ CAMPOS, S.; IGLESIAS GONZÁLEZ, P.A.; SCODELARO BILBAO, P.G.; URANGA, R.; SALVADOR, G.

Chamonix

Conferencia; International Conference on the Bioscience of Lipids; 2016

Alpha-synuclein (α-syn) is a neuronal presynaptic protein whose main function is still unknown. Its most characterized role has been associated withits overexpression and oligomerization in dopaminergic neurons in Parkinson?sdisease (PD) patients. An intriguing and less characterized property of this protein is its lipid binding affinity. Our purpose in this work was to characterize the role of α-syn variants,wild-type and A53T mutant, in neuronal lipid metabolism and signaling. To this end, we worked witha N27 dopaminergic neuronal cell line stably transfected with A53T α-syn(a variant overexpressed in early-onset PD) and IMR-32 human neuroblastoma cells stably expressing human wild type α-syn (WT). Both cell lines were used to evaluate the status of lipid metabolism and signaling with respect to untransfected cells.Neurons stably transfected with both variants of α-syn (A53T and WT) displayed increased levels ofα-syn protein. The expression of α-synmainly co-localized with the neuronal marker choline acetyltransferase, whereas the phosphorylated form was mainly located in the nucleus in WT α-syn neurons. Overexpression of both α-synvariants also triggered anincrease in fatty acid synthase (FAS) expression. In line with this, A53Tα-syn overexpressing neurons displayed increased fatty acids (FA)content and exhibited high resistance to cerulenin and triacsin, both potent inhibitors of FAS and acyl-CoA synthase. As a consequence of the increased FA availability, both α-syn-overexpressingcell lines showed increased acylation in the triacylglycerol (TAG) fraction and A53Tα-synneurons displayed higher TAG content than non-transfected neurons.We also characterized the role of α-syn in lipid signaling by evaluating phosphatidic acid (PA) and phosphatidylinositol (PI) signaling in neurons that overexpressed WT α-syn. PA is a lipid second messenger that transiently peaks in response to multiple stimuli. Phospholipase D (PLD) and diacylglycerol kinase (DAGK) are responsible for the transient increase of PA during cell signaling. Previous evidences described an inhibitory role of α-syn for PLDs. In our experimental model, WT α-syn overexpressingneurons displayed diminished DAGKζ expression and decreased viability in the presence of PLD2 inhibitor EVJ. Regarding PI-derived signaling, we also checked the role of PI-phospholipase C and PI3-kinase. The blockage of PI3-kinase signaling enhanced cell death in WT α-synoverexpressingneurons.Our results clearly show that α-syn is not only a key modulator of lipid metabolism by promoting an increase in FA availability but also a regulator of PA-derived signaling. Based on thisexperimental evidence, we postulate that the above-mentionedlipid pathways could become an emerging therapeutic target crucial tothe determination of neuronal fate during neurodegeneration in PD.