Acyl-CoA synthetase activity links wild-type but not mutant α-synuclein to brain arachidonate metabolism
Acyl-CoA synthetase activity links wild-type but not mutant α-synuclein to brain arachidonate metabolism
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DOI：
10.1021/bi0600289
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发表时间：
2006-06-06
期刊：
影响因子：
2.9
通讯作者：
Murphy, Eric J.
中科院分区：
文献类型：
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作者：
Golovko, Mikhail Y.;Rosenberger, Thad A.;Murphy, Eric J.
由于α-突触核蛋白（Snca）在脑脂质代谢中起作用，我们使用Snca（-/-）小鼠体内测定了α-突触核蛋白的丢失对脑花生四烯酸（20：4 n-6）代谢的影响。我们测量[1-C-14]20：4 n-6掺入和周转动力学脑磷脂使用一个既定的稳态动力学模型。肝脏用作阴性对照，组间未观察到变化。在Snca-/-脑中，20：4 n-6-CoA质量和微粒体酰基辅酶A合成酶（Acsl）活性向20：4 n-6显著降低。微粒体Acsl活性在添加外源性野生型小鼠或人α-突触核蛋白后完全恢复，但A30 P、E46 K和A53 T形式的α-突触核蛋白不能恢复。Acsl和酰基辅酶A水解酶的表达在组间没有差异。20：4 n-6进入脑磷脂池的掺入和周转明显减少。稀释系数I（表明酰基-CoA池和脑磷脂之间的20：4 n-6再循环）增加了3.3倍，表明相对于从磷脂再循环的20：4 n-6，更多的20：4 n-6从血浆进入20：4 n-6-CoA池。这与在Snca-/-小鼠中观察到的Acsl活性降低一致。使用滴定微量热法，我们确定α-突触核蛋白结合游离的20：4 n-6（Kd = 3.7 μ M），但不结合20：4 n-6-CoA。这些数据表明α-突触核蛋白参与底物呈递至Acsl，而不是产物去除。总之，我们的数据表明，α-突触核蛋白在脑20：4 n-6代谢中具有重要作用，通过其调节内质网定位的酰基辅酶A合成酶的活性，虽然突变形式的α-突触核蛋白不能恢复这种活性。
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-C-14]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 I, 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 (K-d = 3.7 mu M) 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.