PDF(Pubmed)
Abstract：
Ectonucleotide pyrophosphatase/phosphodiesterase 1 (ENPP1) codes for a type 2 transmembrane glycoprotein which hydrolyzes extracellular phosphoanhydrides into bio-active molecules that regulate, inter alia, ectopic mineralization, bone formation, vascular endothelial proliferation, and the innate immune response. The clinical phenotypes produced by ENPP1 deficiency are disparate, ranging from life-threatening arterial calcifications to cutaneous hypopigmentation. To investigate associations between disease phenotype and enzyme activity we quantified the enzyme velocities of 29 unique ENPP1 pathogenic variants in 41 patients enrolled in an NIH study along with 33 other variants reported in literature. We correlated the relative enzyme velocities with the presenting clinical diagnoses, performing the catalytic velocity measurements simultaneously in triplicate using a high-throughput assay to reduce experimental variation. We found that ENPP1 variants associated with autosomal dominant phenotypes reduced enzyme velocities by 50 % or more, whereas variants associated with insulin resistance had non-significant effects on enzyme velocity. In Cole disease the catalytic velocities of ENPP1 variants associated with AD forms trended to lower values than those associated with autosomal recessive forms - 8-32 % vs. 33 % of WT, respectively. Additionally, ENPP1 variants leading to life-threatening vascular calcifications in GACI patients had widely variable enzyme activities, ranging from no significant differences compared to WT to the complete abolishment of enzyme velocity. Finally, disease severity in GACI did not correlate with the mean enzyme velocity of the variants present in affected compound heterozygotes but did correlate with the more severely damaging variant. In summary, correlation of ENPP1 enzyme velocity with disease phenotypes demonstrate that enzyme velocities below 50 % of WT levels are likely to occur in the context of autosomal dominant disease (due to a monoallelic variant), and that disease severity in GACI infants correlates with the more severely damaging ENPP1 variant in compound heterozygotes, not the mean velocity of the pathogenic variants present.
摘要：
核苷酸焦磷酸酶/磷酸二酯酶1（ENPP1）编码2型跨膜糖蛋白，该蛋白将细胞外磷酸酐水解为调节生物活性分子，除其他外,异位矿化，骨形成,血管内皮增生,和先天免疫反应。ENPP1缺乏症产生的临床表型是不同的，从危及生命的动脉钙化到皮肤色素沉着不足。为了研究疾病表型与酶活性之间的关联，我们量化了NIH研究中41例患者中29种独特ENPP1致病变体的酶速度以及文献中报道的33种其他变体。我们将相对酶速度与目前的临床诊断相关联，使用高通量测定法一式三份同时进行催化速度测量，以减少实验差异。我们发现与常染色体显性表型相关的ENPP1变异将酶速度降低了50%或更多，而与胰岛素抵抗相关的变异体对酶速度无显著影响.在Cole病中，与AD形式相关的ENPP1变体的催化速度倾向于低于与常染色体隐性形式相关的值-8-32％33%的WT，分别。此外,在GACI患者中导致危及生命的血管钙化的ENPP1变体具有广泛变化的酶活性，从与WT相比没有显着差异到酶速度的完全消除。最后,GACI的疾病严重程度与受影响的复合杂合子中存在的变体的平均酶速度无关,但确实与损伤更严重的变体相关.总之,ENPP1酶速度与疾病表型的相关性表明，低于WT水平的50％的酶速度可能发生在常染色体显性疾病的背景下（由于单等位基因变异），GACI婴儿的疾病严重程度与复合杂合子中损伤更严重的ENPP1变体相关，不是存在的致病变体的平均速度。
