Mutation for Nonsyndromic Mental Retardation in the trans-2-Enoyl-CoA Reductase TER Gene Involved in Fatty Acid Elongation Impairs the Enzyme Activity and Stability, Leading to Change in Sphingolipid Profile
Mutation for Nonsyndromic Mental Retardation in the trans-2-Enoyl-CoA Reductase TER Gene Involved in Fatty Acid Elongation Impairs the Enzyme Activity and Stability, Leading to Change in Sphingolipid Profile
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DOI：
10.1074/jbc.m113.493221
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发表时间：
2013-12-20
影响因子：
4.8
通讯作者：
Kihara, Akio
中科院分区：
文献类型：
--
作者：
Abe, Kensuke;Ohno, Yusuke;Kihara, Akio
背景：超长链脂肪酸（VLCFA）合成所需的反式2-烯基辅酶a还原酶（TER）基因P182L突变导致非综合征性智力迟钝。结果：该突变降低了TER酶的活性和稳定性。结论：TER功能受损影响VLCFA合成，从而改变细胞鞘脂谱。意义：维持适当的VLCFA水平可能对神经功能很重要。甚长链脂肪酸（VLCFAs，链长b> C20）存在于全身组织中，是由四个连续的酶促反应组成的脂肪酸（FA）延伸循环的重复合成。在哺乳动物中，TER基因是唯一编码反式2-烯基辅酶a还原酶的基因，该酶催化FA延伸周期的第四个反应。TER P182L突变是非综合征性智力低下的致病突变。这种突变用亮氨酸代替了TER酶182号氨基酸上的脯氨酸残基。目前，TER P182L突变导致非综合征性智力低下的机制尚不清楚。为了了解该突变对TER酶和VLCFA合成的影响，我们利用转染TERP182L突变基因的酵母和哺乳动物细胞对TERP182L突变酶进行了生化表征，并分析了纯合子TERP182L突变的b淋巴母细胞样细胞系（TERP182L/P182L b淋巴母细胞样细胞系）FA伸长周期。我们发现，TERP182L突变酶表现出反式2-烯酰辅酶a还原酶活性和蛋白质稳定性降低，从而损害VLCFA合成，进而改变TERP182L/P182L b淋巴母细胞样细胞系的鞘脂谱（即C24鞘磷脂和C24神经酰胺水平降低）。我们还发现，除了TER酶催化的第4个反应外，FA延伸周期中的第3个反应也受到TER P182L突变的影响。这些发现为与这种基因突变相关的生化缺陷提供了新的见解。
Background: The P182L mutation in the trans-2-enoyl-CoA reductase (TER) gene required for very long-chain fatty acid (VLCFA) synthesis causes nonsyndromic mental retardation. Results: This mutation reduces the activity and stability of the TER enzyme. Conclusion: The impaired TER function affects VLCFA synthesis and thereby alters the cellular sphingolipid profile. Significance: Maintenance of a proper VLCFA level may be important for neural function.Very long-chain fatty acids (VLCFAs, chain length >C20) exist in tissues throughout the body and are synthesized by repetition of the fatty acid (FA) elongation cycle composed of four successive enzymatic reactions. In mammals, the TER gene is the only gene encoding trans-2-enoyl-CoA reductase, which catalyzes the fourth reaction in the FA elongation cycle. The TER P182L mutation is the pathogenic mutation for nonsyndromic mental retardation. This mutation substitutes a leucine for a proline residue at amino acid 182 in the TER enzyme. Currently, the mechanism by which the TER P182L mutation causes nonsyndromic mental retardation is unknown. To understand the effect of this mutation on the TER enzyme and VLCFA synthesis, we have biochemically characterized the TER P182L mutant enzyme using yeast and mammalian cells transfected with the TER P182L mutant gene and analyzed the FA elongation cycle in the B-lymphoblastoid cell line with the homozygous TER P182L mutation (TERP182L/P182L B-lymphoblastoid cell line). We have found that TER P182L mutant enzyme exhibits reduced trans-2-enoyl-CoA reductase activity and protein stability, thereby impairing VLCFA synthesis and, in turn, altering the sphingolipid profile (i.e. decreased level of C24 sphingomyelin and C24 ceramide) in the TERP182L/P182L B-lymphoblastoid cell line. We have also found that in addition to the TER enzyme-catalyzed fourth reaction, the third reaction in the FA elongation cycle is affected by the TER P182L mutation. These findings provide new insight into the biochemical defects associated with this genetic mutation.