cDNA cloning of cholesterol 24-hydroxylase, a mediator of cholesterol homeostasis in the brain
cDNA cloning of cholesterol 24-hydroxylase, a mediator of cholesterol homeostasis in the brain
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DOI：
10.1073/pnas.96.13.7238
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发表时间：
1999-06-22
影响因子：
11.1
通讯作者：
Russell, DW
中科院分区：
文献类型：
--
作者：
Lund, EG;Guileyardo, JM;Russell, DW
脑中胆固醇的周转被认为是通过将过量的胆固醇转化为24 S-羟基胆固醇而发生的，24 S-羟基胆固醇是一种容易从中枢神经系统分泌到血浆中的osysterol。为了从分子水平深入了解胆固醇代谢途径，我们使用表达克隆技术分离编码鼠和人胆固醇24-羟化酶的cDNA。DNA序列分析表明，这两种蛋白质定位于内质网，共享95%的同一性，并代表一个新的细胞色素P450亚家族（CYP 46）。当转染到培养的细胞中时，cDNA产生将胆固醇转化为24 S-羟基胆固醇的酶活性，并且在较小程度上转化为25-羟基胆固醇。胆固醇24-羟化酶基因包含15个外显子，位于人类染色体14q32.1。通过RNA和蛋白质印迹法判断，胆固醇24-羟化酶主要在脑中表达。原位mRNA杂交和免疫组织化学将该P450的表达定位于大脑多个亚区的神经元。新生小鼠血清中24 S-羟基胆固醇的浓度较低，在出生后第12至15天达到峰值，此后下降至基线水平，相反，胆固醇24-羟化酶蛋白在出生时首先在小鼠脑中检测到，并随着年龄的增长继续积累。我们的结论是，克隆的cDNA编码的胆固醇24-羟化酶，合成氧化固醇在大脑的神经元和分泌的24 S-羟基胆固醇从这个组织在小鼠发育调节。
The turnover of cholesterol in the brain is thought to occur via conversion of excess cholesterol into 24S-hydroxycholesterol, an osysterol that is readily secreted from the central nervous system into the plasma. To gain molecular insight into this pathway of cholesterol metabolism, we used expression cloning to isolate cDNAs that encode murine and human cholesterol 24-hydroxylases. DNA sequence analysis indicates that both proteins are localized to the endoplasmic reticulum, share 95% identity, and represent a new cytochrome P450 subfamily (CYP46). When transfected into cultured cells, the cDNAs produce an enzymatic activity that converts cholesterol into 24S-hydroxycholesterol, and to a lesser extent, 25-hydroxycholesterol. The cholesterol 24-hydroxylase gene contains 15 exons and is located on human chromosome 14q32.1. Cholesterol 24-hydroxylase is expressed predominantly in the brain as judged by RNA and protein blotting. In situ mRNA hybridization and immunohistochemistry localize the expression of this P450 to neurons in multiple subregions of the brain. The concentrations of 24S-hydroxycholesterol in serum are low in newborn mice, reach a peak between postnatal days 12 and 15, and thereafter decline to baseline levels, In contrast, cholesterol 24-hydroxylase protein is first detected in the brain of mice at birth and continues to accumulate with age. We conclude that the cloned cDNAs encode cholesterol 24-hydroxylases that synthesize oxysterols in neurons of the brain and that secretions of 24S-hydroxycholesterol from this tissue in the mouse is developmentally regulated.