Characterization of the interplay between SEC23A and the MAPK signaling pathway

SEC23A 和 MAPK 信号通路之间相互作用的表征

• 批准号: 8224772
• 负责人: Jinoh Kim
• 金额: $ 23.09万
• 依托单位: UNIVERSITY OF CALIFORNIA AT DAVIS
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-05-17 至 2014-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8224772
• 关键词: Accounting; Affect; Biological Assay; COPII-Coated Vesicles; Cataract; Cell Line; Cells; Congenital Abnormality; Craniosynostosis; Defect; Development; Disease; Dysplasia; Elements; Embryo; Endoplasmic Reticulum; Epidermal Growth Factor; Epidermal Growth Factor Receptor; Face; Fibroblast Growth Factor Receptors; Fibroblasts; Golgi Apparatus; Growth; Human; In Vitro; Joint structure of suture of skull; Link; MAPK3 gene; Mediating; Membrane; Membrane Proteins; Microscopy; Missense Mutation; Mitogen-Activated Protein Kinases; Modeling; Molecular; Monitor; Mus; Mutation; PDGFRB gene; Pathway interactions; Patients; Pattern; Phenotype; Phosphorylation; Play; Procollagen; Protein Export Pathway; Proteins; RNA Interference; Receptor Protein-Tyrosine Kinases; Role; Screening procedure; Signal Pathway; Signal Transduction; Site; Surgical sutures; Testing; Translating; Transport Vesicles; Vesicle; Yeasts; craniofacial; design; inhibitor/antagonist; insight; interest; malformation; premature; protein transport; secretory protein; skeletal; suture fusion; trafficking; treatment strategy

DESCRIPTION (provided by applicant): Cranio-lenticulo-sutural-dysplasia (CLSD) is a congenital autosomal recessive disease characterized by facial dysmorphisms, skeletal defects, late-closing fontanels, and cataracts. Missense mutations (F382L and M702V) in SEC23A have been linked to CLSD. SEC23A is an essential component of the COPII-coated vesicles that transport secretory and membrane proteins from the endoplasmic reticulum (ER) to the ER-Golgi intermediate compartment (ERGIC) or cis-Golgi. COPII proteins (SAR1, SEC13/31, and SEC23/24) deform the ER membrane into a small transport vesicle. During this vesicle assembly, the COPII proteins load cargo molecules into a budding vesicle. Defects in COPII proteins cause inefficient export of cargo proteins from the ER, resulting in gross dilation of the ER in yeast. Fibroblasts derived from CLSD patients also show distention of the ER, clearly demonstrating an ER export defect. Surprisingly, however, most cargo molecules traffic normally in M702V fibroblasts. This result suggests that M702V SEC23A blocks ER export in a cargo specific manner and that a trafficking defect of a specific set of cargo proteins is the underlying cause of this disease. Remarkably, we recently observed that the mitogen-activated protein kinase (MAPK) signaling is down regulated in the M702V fibroblasts. This is interesting because the MAPK pathway relays signals from receptor tyrosine kinases (RTKs) to downstream effectors. Constitutive hyperactivation of a RTK, fibroblast growth factor receptor (FGFR), accounts for most cases of familial craniosynostosis (CS), the premature fusion of the cranial sutures. Lessening this aberrant MAPK signaling by an inhibitor of this pathway was sufficient to rescue CS phenotypes in mice. Because excessive FGFR-MAPK signaling leads to premature closure of craniofacial sutures, deficient MAPK signaling in the M702V cells likely contributes to delayed closure of craniofacial sutures in CLSD. Thus, M702V SEC23A may specifically inhibit trafficking of RTKs. A recent study has revealed that activation of extracellular signal-regulated kinase 2 (a MAPK) by epidermal growth factor enhances formation of ER exit sites, indicating an efficient assembly of COPII vesicles. Considering the notion that hyperactivation of the MAPK signaling contributes to CS, the premature fusion of cranial sutures may be mediated by an increased efficiency of ER export. Thus, understanding the interplay between the RTK signaling and the COPII vesicle assembly via the MAPK pathway can provide a fundamentally critical insight into CLSD, CS, and other related diseases. We hypothesize that the MAPK pathway connects signaling from RTKs to the ER export machinery. This model predicts that in CLSD, deficiency of SEC23A causes inefficient trafficking of RTKs, resulting in reduced MAPK signaling and that in CS, enhanced FGFR-MAPK signaling causes excessively increased ER export. To test these predictions, we will test if a SEC23A deficit blocks ER export of RTKs and influences the MAPK signaling (CLSD case) and we will test whether the overactive FGFR-MAPK signaling causes an excessive assembly of COPII vesicles (CS case). PUBLIC HEALTH RELEVANCE: Cranio-lenticulo-sutural dysplasia (CLSD) is caused by mutations (F382L or M702V) in SEC23A, a component of COPII machinery that is critical for protein export from the endoplasmic reticulum (ER). We recently discovered that the ER export defect in M702V fibroblasts cells is cargo specific and that the MAPK signaling pathway is subdued possibly because of a trafficking defect of receptor tyrosine kinases including FGFR. By using Sec23a-deficient human and murine cell lines, we will characterize the interplay between ER export machinery and the MAPK signaling pathway in the context of craniofacial development, which will allow us to decipher the significance of protein transport on craniofacial development and to design new strategies for treatment of craniofacial defects.

描述（申请人提供）：颅透镜缝发育不良（CLSD）是一种先天性常染色体隐性遗传病，其特征为面部畸形、骨骼缺陷、迟闭囟门和白内障。SEC23A中的错义突变（F382L和M702V）与CLSD有关。SEC23A是将分泌蛋白和膜蛋白从内质网（ER）转运到ER-高尔基体中间室（ERGIC）或顺式高尔基体的copii包被囊泡的重要组成部分。COPII蛋白（SAR1， SEC13/31和SEC23/24）使内质网膜变形成一个小的运输囊泡。在这个囊泡组装过程中，COPII蛋白将货物分子装载到正在萌发的囊泡中。COPII蛋白的缺陷导致内质网货物蛋白的输出效率低下，导致酵母菌内质网的总体扩张。来自CLSD患者的成纤维细胞也显示内质网扩张，清楚地表明内质网输出缺陷。然而，令人惊讶的是，大多数货物分子在M702V成纤维细胞中正常运输。这一结果表明，M702V SEC23A以货物特异性方式阻断ER出口，一组特定货物蛋白的运输缺陷是这种疾病的潜在原因。值得注意的是，我们最近观察到丝裂原活化蛋白激酶（MAPK）信号在M702V成纤维细胞中下调。这很有趣，因为MAPK途径将来自受体酪氨酸激酶（rtk）的信号传递给下游效应器。成纤维细胞生长因子受体（FGFR） RTK的构成性过度激活是大多数家族性颅缝闭合（CS）的原因，即颅缝的过早融合。通过该途径的抑制剂减少这种异常的MAPK信号传导足以挽救小鼠的CS表型。由于过度的FGFR-MAPK信号传导导致颅面缝合线过早闭合，M702V细胞中MAPK信号传导不足可能导致CLSD颅面缝合线延迟闭合。因此，M702V SEC23A可能特异性抑制rtk的贩运。最近的一项研究表明，表皮生长因子激活细胞外信号调节激酶2 （A MAPK）可促进内质网出口位点的形成，表明COPII囊泡的有效组装。考虑到MAPK信号的过度激活有助于CS，颅缝的过早融合可能是由内质网输出效率的提高介导的。因此，通过MAPK途径了解RTK信号和COPII囊泡组装之间的相互作用可以为CLSD、CS和其他相关疾病提供根本性的关键见解。我们假设MAPK通路将rtk的信号传导连接到内质网输出机制。该模型预测，在CLSD中，SEC23A的缺乏导致rtk的低效率贩运，导致MAPK信号的减少，而在CS中，FGFR-MAPK信号的增强导致ER输出过度增加。为了验证这些预测，我们将测试SEC23A缺陷是否会阻碍rtk的ER输出并影响MAPK信号传导（CLSD病例），我们将测试过度活跃的FGFR-MAPK信号传导是否会导致COPII囊泡的过度组装（CS病例）。