Novel patient missense mutations in the HSD17B10 gene affect dehydrogenase and mitochondrial tRNA modification functions of the encoded protein
Novel patient missense mutations in the HSD17B10 gene affect dehydrogenase and mitochondrial tRNA modification functions of the encoded protein
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DOI：
10.1016/j.bbadis.2017.09.002
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发表时间：
2017-12-01
影响因子：
6.2
通讯作者：
Yue, Wyatt W.
中科院分区：
文献类型：
--
作者：
Oerum, Stephanie;Roovers, Martine;Yue, Wyatt W.
MRPP2（也称为HSD10/SDR5C1）是一种多功能蛋白，具有催化和非催化功能。该蛋白属于短链脱氢酶/还原酶（SDR）家族，参与体内异亮氨酸的分解代谢和体外类固醇代谢。MRPP2还与MRPP1（也称为TRMT10C）蛋白共同作用于线粒体tRNA第9位嘌呤的n1甲基化，并与MRPP1和MRPP3（也称为prop）蛋白共同作用于线粒体前体tRNA的5'端加工。编码MRPP2蛋白的HSD17B10基因的遗传突变导致以进行性神经变性、心肌病或两者兼而有之为特征的儿童疾病。在这里，我们报告了两例HSD17B10基因（C . 34g > C和C . 526g > A）的新型错义突变，导致p.V12L和p.V176M的替换。Va112和Va1176是位于MRPP2结构不同区域的高度保守残基。表达重组突变蛋白并对其进行生化表征，以研究其对MRPP2及其相关复合物功能的体外影响。与野生型相比，两种突变蛋白的脱氢酶、甲基转移酶和tRNA加工活性均显著降低，这与携带p.V12L的蛋白稳定性降低有关，而携带p.V176M的蛋白则表现出动力学和复合物形成受损。因此，本研究确定了两种不同的分子机制来解释新的错义患者突变的生化缺陷。
MRPP2 (also known as HSD10/SDR5C1) is a multifunctional protein that harbours both catalytic and non catalytic functions. The protein belongs to the short-chain dehydrogenase/reductases (SDR) family and is involved in the catabolism of isoleucine in vivo and steroid metabolism in vitro. MRPP2 also moonlights in a complex with the MRPP1 (also known as TRMT10C) protein for N1-methylation of purines at position 9 of mitochondrial tRNA, and in a complex with MRPP1 and MRPP3 (also known as PRORP) proteins for 5'-end processing of mitochondrial precursor tRNA. Inherited mutations in the HSD17B10 gene encoding MRPP2 protein lead to a childhood disorder characterised by progressive neurodegeneration, cardiomyopathy or both. Here we report two patients with novel missense mutations in the HSD17B10 gene (c.34G > C and c.526G > A), resulting in the p.V12L and p.V176M substitutions. Va112 and Va1176 are highly conserved residues located at different regions of the MRPP2 structure. Recombinant mutant proteins were expressed and characterised biochemically to investigate their effects towards the functions of MRPP2 and associated complexes in vitro. Both mutant proteins showed significant reduction in the dehydrogenase, methyltransferase and tRNA processing activities compared to wildtype, associated with reduced stability for protein with p.V12L, whereas the protein carrying p.V176M showed impaired kinetics and complex formation. This study therefore identified two distinctive molecular mechanisms to explain the biochemical defects for the novel missense patient mutations.