title: Acyl-CoA synthetase activity links wild-type but not mutant alpha-synuclein to brain arachidonate metabolism.
abstract: Because alpha-synuclein (Snca) has a role in brain lipid metabolism, we determined the impact that the loss of alpha-synuclein had on brain arachidonic acid (20:4n-6) metabolism in vivo using Snca-/- mice. We measured [1-(14)C]20:4n-6 incorporation and turnover kinetics in brain phospholipids using an established steady-state kinetic model. Liver was used as a negative control, and no changes were observed between groups. In Snca-/- brains, there was a marked reduction in 20:4n-6-CoA mass and in microsomal acyl-CoA synthetase (Acsl) activity toward 20:4n-6. Microsomal Acsl activity was completely restored after the addition of exogenous wild-type mouse or human alpha-synuclein, but not by A30P, E46K, and A53T forms of alpha-synuclein. Acsl and acyl-CoA hydrolase expression was not different between groups. The incorporation and turnover of 20:4n-6 into brain phospholipid pools were markedly reduced. The dilution coefficient lambda, which indicates 20:4n-6 recycling between the acyl-CoA pool and brain phospholipids, was increased 3.3-fold, indicating more 20:4n-6 was entering the 20:4n-6-CoA pool from the plasma relative to that being recycled from the phospholipids. This is consistent with the reduction in Acsl activity observed in the Snca-/- mice. Using titration microcalorimetry, we determined that alpha-synuclein bound free 20:4n-6 (Kd = 3.7 microM) but did not bind 20:4n-6-CoA. These data suggest alpha-synuclein is involved in substrate presentation to Acsl rather than product removal. In summary, our data demonstrate that alpha-synuclein has a major role in brain 20:4n-6 metabolism through its modulation of endoplasmic reticulum-localized acyl-CoA synthetase activity, although mutant forms of alpha-synuclein fail to restore this activity.
authors.affiliation: Department of Pharmacology, Physiology, and Therapeutics, University of North Dakota, Grand Forks, North Dakota 58202-9037, USA.
authors.forename: Mikhail Y
authors.initials: MY
authors.lastname: Golovko
authors.forename: Thad A
authors.initials: TA
authors.lastname: Rosenberger
authors.forename: Nils J
authors.initials: NJ
authors.lastname: Faergeman
authors.forename: Søren
authors.initials: S
authors.lastname: Feddersen
authors.forename: Nelson B
authors.initials: NB
authors.lastname: Cole
authors.forename: Ingrid
authors.initials: I
authors.lastname: Pribill
authors.forename: Johannes
authors.initials: J
authors.lastname: Berger
authors.forename: Robert L
authors.initials: RL
authors.lastname: Nussbaum
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Murphy
mesh_terms: D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism*; D001921:Brain / Q000201:enzymology*; D003066:Coenzyme A Ligases / Q000032:analysis / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000201:enzymology; D051379:Mice; D008817:Mice, Mutant Strains; D008861:Microsomes / Q000201:enzymology; D009154:Mutation; D051844:alpha-Synuclein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051844:alpha-Synuclein; D016718:Arachidonic Acid; D003066:Coenzyme A Ligases