N-terminal residues regulate proteasomal degradation of AANAT.
N-terminal residues regulate proteasomal degradation of AANAT.
复制标题
N 末端残基调节 AANAT 的蛋白酶体降解。
DOI：
10.1111/j.1600-079x.2010.00753.x
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发表时间：
2010
影响因子：
10.3
通讯作者：
Borjigin,Jimo
中科院分区：
文献类型：
--
作者：
Huang,Zheping;Liu,Tiecheng;Borjigin,Jimo
5-羟色胺N-乙酰转移酶（AANAT）催化5-羟色胺转化为N-乙酰5-羟色胺，后者是褪黑激素形成的直接前体。虽然已知AANAT通过蛋白酶体蛋白水解降解，但详细机制尚未确定。在本文中，我们测试了在体内的作用，蛋白酶体抑制AANAT活性和褪黑激素的释放，并检查AANAT中的氨基酸残基，有助于蛋白酶体降解。我们已经证明，在体内抑制完整松果体中的蛋白酶体活性不能防止光诱导的褪黑素分泌抑制。此外，在稳定表达AANAT的细胞系中，抑制蛋白酶体蛋白水解导致AANAT蛋白大量积累，同样不能增加AANAT酶活性，与积累的蛋白量成比例。AANAT的定点突变分析显示AANAT降解不依赖于赖氨酸和两个表面半胱氨酸残基。N-末端的缺失分析鉴定了第二个氨基酸亮氨酸（L2）为有助于AANAT蛋白的蛋白酶体蛋白水解的关键残基。这些结果表明，大鼠AANAT蛋白通过蛋白酶体蛋白水解的N末端规则途径降解，N末端的亮氨酸似乎是N末端规则途径识别的关键残基。
SerotoninN‐acetyltransferase (AANAT) catalyzes the conversion of serotonin toN‐acetylserotonin, which is the immediate precursor for formation of melatonin. Although it is known that AANAT is degraded via the proteasomal proteolysis, detailed mechanisms are not defined. In this paper, we tested the in vivo role of proteasome inhibition on AANAT activity and melatonin release and examined the amino acid residues in AANAT that contribute to the proteasome degradation. We have shown that inhibition of proteasome activities in vivo in the intact pineal gland fails to prevent the light‐induced suppression of melatonin secretion. Furthermore, in cell lines stably expressing AANAT, inhibition of proteasomal proteolysis, which resulted in a large accumulation of AANAT protein, similarly failed to increase AANAT enzyme activity proportional to the amount of proteins accumulated. Site‐directed mutagenesis analysis of AANAT revealed that the AANAT degradation is independent of lysine and the two surface cysteine residues. Deletion analysis of N‐terminus identified the second amino acid leucine (L2) as the key residue that contributes to the proteasomal proteolysis of AANAT protein. These results suggest that rat AANAT protein is degraded via the N‐end rule pathway of proteasomal proteolysis and the leucine at the N‐terminus appears to be the key residue recognized by N‐end rule pathway.