PDF(Pubmed)
Abstract：
GDP-mannose pyrophosphorylase B (GMPPB) loss-of-function is associated with muscular dystrophy and variable additional neurological symptoms. GMPPB facilitates the catalytic conversion of mannose-1-phosphate and GTP to GDP-mannose, which serves as a mannose donor for glycosylation. The activity of GMPPB is regulated by its non-catalytic paralogue GMPPA, which can bind GDP-mannose and interact with GMPPB, thereby acting as an allosteric feedback inhibitor of GMPPB. Using pulldown, immunoprecipitation, turnover experiments as well as immunolabeling and enzyme activity assays, we provide first direct evidence that GMPPB activity is regulated by ubiquitination. We further show that the E3 ubiquitin ligase TRIM67 interacts with GMPPB and that knockdown of TRM67 reduces ubiquitination of GMPPB, thus reflecting a candidate E3 ligase for the ubiquitination of GMPPB. While the inhibition of GMPPB ubiquitination decreases its enzymatic activity, its ubiquitination neither affects its interaction with GMPPA nor its turnover. Taken together, we show that the ubiquitination of GMPPB represents another level of regulation of GDP-mannose supply.
摘要：
GDP-甘露糖焦磷酸化酶B（GMPPB）功能丧失与肌营养不良和其他神经系统症状有关。GMPPB促进甘露糖-1-磷酸和GTP催化转化为GDP-甘露糖,作为糖基化的甘露糖供体。GMPPB的活性受其非催化旁系同源物GMPPA的调控,它可以结合GDP-甘露糖并与GMPPB相互作用，从而充当GMPPB的变构反馈抑制剂。使用下拉，免疫沉淀,周转实验以及免疫标记和酶活性测定，我们提供了GMPPB活性受泛素化调节的第一个直接证据。我们进一步表明E3泛素连接酶TRIM67与GMPPB相互作用，并且TRM67的敲低降低了GMPPB的泛素化，因此反映了GMPPB泛素化的候选E3连接酶。虽然抑制GMPPB的泛素化会降低其酶活性，其泛素化既不影响其与GMPPA的相互作用，也不影响其周转。一起来看,我们表明GMPPB的泛素化代表了GDP-甘露糖供应的另一个调节水平。
