Investigations on hyperphosphorylation of paratarg-7, a significant risk factor and frequent antigenic target of paraproteins in MGUS and multiple myeloma.

对 paratarg-7 过度磷酸化的研究，这是 MGUS 和多发性骨髓瘤中副蛋白的一个重要危险因素和常见抗原靶点。

• 批准号: 174774150
• 负责人: Professor Dr. Michael Pfreundschuh (†)
• 金额: --
• 依托单位: Klinik für Innere Medizin I - Onkologie, Hämatologie, Klinische Immunologie und Rheumatologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2015-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/174774150?language=en
• 关键词: Investigations; hyperphosphorylation; paratarg; significant; risk

In previous studies we had identified and characterized hyperphosphorylated paratarg-7 (pP-7) as the antigenic target of 15% of all paraproteins of the IgA and IgG type and of 11% of all IgM paraproteins. Moreover, we had shown that pP-7 carriership is the strongest risk factor to develop MGUS/MM/WM known to date and is inherited as an autosomal-dominant trait. During the first three years of DFG support for this project we showed that pP-7 is the target of >1/3 (!) of paraproteins in African-American MGUS/MM patients underlining the importance of pP-7 in the pathogenesis of these diseases. Moreover, we succeeded in identifying additional autoantigenic targets of paraproteins and demonstrated that all these autoantigenic targets were hyperphosphorylated in the respective patients compared to healthy controls (and also inherited autosomal-dominantly), demonstrating that hyperphosphorylation of autoantigenic paraprotein targets is frequent in MGUS/MM/WM patients. Investigating the mechanisms underlying the hyerphosphorylation of the paraprotein targets we demonstrated that in healthy controls P-7 is hyerphosphorylated at serine 17 after stimulation by PKCzeta, and dephosphorylated by protein phosphatase 2A, as are all other autoantigenic paratargs. In pP-7 carriers and carriers of all other hyperphosphorylated autoantigenic paraproteins targets, dephosphorylation of pP-7 is defective due to an exchange of the regulatory subunit B55delta by B56gamma3 in the trimeric PP2A enzyme complex. Sequencing of paratargs and of the for the phosphorylation state responsible PKCzeta as well as the expressed subunits of PP2A, did not reveal SNPs or mutations that were associated with the hyperphosphorylation of P-7. Similarly, whole-exome sequencing which was performed twice in cooperation with two independent cooperating partners did not identify a genetic variant responsible for P-7 hyperphosphorylation, nor did whole-genome methylation analysis. However, a single nucleotide polymorphisms and microsatellite-based genome-wide linkage analysis identified a 4.3 Mb long region of chromosome 4q35 to locate the genetic variant responsible for the hyperphosphorylation of P-7 with a LOD score of 6 (!). In the suggested second period of DFG support, we will narrow-down the DNA region using a functional approach with wtP-7 and pP-7 LCLS and investigate the pathways leading from the respective genetic variant of interest to the hyperphosphorylation of autoantigenic targets of paraproteins. Our investigations will yield important and completely novel information on the pathogenesis of MGUS/MM/WM that will go far beyond their role in paratarg-7 hyperphosphorylation.

在以前的研究中，我们已经确定并表征了高度磷酸化的paratarg-7（pP-7）作为15%的伊加和IgG型副蛋白和11%的IgM副蛋白的抗原靶标。此外，我们已经表明，pP-7携带者是迄今为止已知的发展MGUS/MM/WM的最强风险因素，并且作为常染色体显性性状遗传。在DFG对该项目的前三年支持中，我们表明pP-7是>1/3（！）非裔美国人MGUS/MM患者中副蛋白的表达，强调了pP-7在这些疾病发病机制中的重要性。此外，我们成功地鉴定了副蛋白的其他自身抗原靶点，并证明与健康对照组相比，所有这些自身抗原靶点在相应患者中均高度磷酸化（并且也遗传常染色体显性），表明自身抗原副蛋白靶点的高度磷酸化在MGUS/MM/WM患者中很常见。通过研究副蛋白靶点高度磷酸化的潜在机制，我们证明了在健康对照中，在PKCzeta刺激后，P-7在丝氨酸17处高度磷酸化，并被蛋白磷酸酶2A去磷酸化，所有其他自身抗原副蛋白也是如此。在pP-7携带者和所有其他高度磷酸化的自身抗原副蛋白靶的携带者中，由于三聚体PP 2A酶复合物中调节亚基B55 δ被B56 γ 3交换，pP-7的去磷酸化是有缺陷的。对paratargs和负责磷酸化状态的PKCzeta以及PP 2A的表达亚基进行测序，未发现与P-7过度磷酸化相关的SNP或突变。类似地，与两个独立的合作伙伴合作进行两次的全外显子组测序没有鉴定出导致P-7过度磷酸化的遗传变异，全基因组甲基化分析也没有。然而，单核苷酸多态性和基于微卫星的全基因组连锁分析确定了染色体4 q35的4.3 Mb长区域，以定位负责P-7过度磷酸化的遗传变异，LOD评分为6（！）。在建议的DFG支持的第二阶段，我们将使用wtP-7和pP-7 LCLS的功能方法缩小DNA区域，并研究从各自感兴趣的遗传变异到副蛋白自身抗原靶点过度磷酸化的途径。我们的研究将产生关于MGUS/MM/WM发病机制的重要和全新的信息，这些信息将远远超出它们在paratarg-7过度磷酸化中的作用。