Centro de Diagnóstico de Enfermedades Moleculares, Centro de Biología Molecular-SO UAM-CSIC, Universidad Autónoma de Madrid, Campus de Cantoblanco, 28049 Madrid / Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.
J Inherit Metab Dis. 2011 Aug;34(4):929-39. doi: 10.1007/s10545-011-9328-2. Epub 2011 May 4.
Deficiency of phosphomannomutase (PMM2, MIM#601785) is the most common congenital disorder of glycosylation. Herein we report the genetic analysis of 22 Spanish PMM2 deficient patients and the functional analysis of 14 nucleotide changes in a prokaryotic expression system in order to elucidate their molecular pathogenesis. PMM2 activity assay revealed the presence of six protein changes with no enzymatic activities (p.R123Q, p.R141H, p.F157S, p.P184T, p.F207S and p.D209G) and seven mild protein changes with residual activities ranging from 16 to 54% (p.L32R, p.V44A p.D65Y, p.P113L p.T118S, p.T237M and p.C241S) and also one variant change with normal activity (p.E197A). The results obtained from Western blot analysis, degradation time courses of 11 protein changes and structural analysis of the PMM2 protein, suggest that the loss-of-function of most mutant proteins is based on their increased susceptibility to degradation or aggregation compared to the wild type protein, considering PMM2 deficiency as a conformational disease. We have identified exclusively catalytic protein change (p.D209G), catalytic protein changes affecting protein stability (p.R123Q and p.R141H), two protein changes disrupting the dimer interface (p.P113L and p.T118S) and several misfolding changes (p.L32R, p.V44A, p.D65Y, p.F157S, p.P184T, p.F207S, p.T237M and p.C241S). Our current work opens a promising therapeutic option using pharmacological chaperones to revert the effect of the characterized misfolding mutations identified in a wide range of PMM2 deficient patients.
磷酸甘露糖变位酶（PMM2，MIM#601785）缺乏症是最常见的先天性糖基化缺陷疾病。在此，我们报告了对 22 名西班牙 PMM2 缺乏症患者进行的基因分析，以及在原核表达系统中对 14 个核苷酸变化的功能分析，以阐明其分子发病机制。PMM2 活性测定显示存在 6 种无酶活性的蛋白改变（p.R123Q、p.R141H、p.F157S、p.P184T、p.F207S 和 p.D209G）和 7 种轻度蛋白改变，残留活性范围为 16-54%（p.L32R、p.V44A、p.D65Y、p.P113L、p.T118S、p.T237M 和 p.C241S），还有一种变异改变具有正常活性（p.E197A）。Western blot 分析、11 种蛋白改变的降解时间过程和 PMM2 蛋白的结构分析结果表明，大多数突变蛋白的功能丧失是基于其与野生型蛋白相比更容易降解或聚集，考虑到 PMM2 缺乏症是一种构象疾病。我们已经确定了唯一的催化蛋白改变（p.D209G）、影响蛋白稳定性的催化蛋白改变（p.R123Q 和 p.R141H）、破坏二聚体界面的两种蛋白改变（p.P113L 和 p.T118S）以及几种错误折叠改变（p.L32R、p.V44A、p.D65Y、p.F157S、p.P184T、p.F207S、p.T237M 和 p.C241S）。我们目前的工作为使用药理学伴侣来逆转在广泛的 PMM2 缺乏症患者中鉴定出的特征性错误折叠突变的影响提供了一个有前途的治疗选择。
