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: 8470619
• 负责人: Jinoh Kim
• 金额: $ 18.48万
• 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 2015-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8470619
• 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; Signal Pathway; Signal Transduction; Site; Surgical sutures; Testing; Translating; Transport Vesicles; Vesicle; Yeasts; craniofacial; design; inhibitor/antagonist; insight; interest; malformation; premature; protein transport; screening; 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).

描述（由申请人提供）：颅骨-晶状体-缝线发育不良（CLSD）是一种先天性常染色体隐性遗传疾病，其特征为面部畸形、骨骼缺陷、囟门晚闭和白内障。 SEC23A 中的错义突变（F382L 和 M702V）与 CLSD 相关。 SEC23A 是 COPII 包被囊泡的重要组成部分，可将分泌蛋白和膜蛋白从内质网 (ER) 转运至 ER-高尔基中间室 (ERGIC) 或顺式高尔基体。 COPII 蛋白（SAR1、SEC13/31 和 SEC23/24）使 ER 膜变形为小转运囊泡。在囊泡组装过程中，COPII 蛋白将货物分子装载到出芽的囊泡中。 COPII 蛋白的缺陷导致内质网中货物蛋白的输出效率低下，从而导致酵母中内质网的总体扩张。来自 CLSD 患者的成纤维细胞也显示 ER 扩张，清楚地表明 ER 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 输出，并且一组特定货物蛋白的运输缺陷是这种疾病的根本原因。值得注意的是，我们最近观察到丝裂原激活蛋白激酶 (MAPK) 信号在 M702V 成纤维细胞中下调。这很有趣，因为 MAPK 通路将信号从受体酪氨酸激酶 (RTK) 传递到下游效应器。 RTK、成纤维细胞生长因子受体 (FGFR) 的组成性过度激活是家族性颅缝早闭 (CS)（颅骨缝过早融合）病例的大部分原因。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过早闭合，因此 M702V 细胞中 MAPK 信号传导缺陷可能导致 CLSD 中颅面缝的延迟闭合。因此，M702V SEC23A 可能特异性抑制 RTK 的运输。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 (MAPK) 可增强 ER 出口位点的形成，表明 COPII 囊泡的有效组装。考虑到 MAPK 信号传导的过度激活有助于 CS，颅骨缝的过早融合可能是由 ER 输出效率增加介导的。因此，通过 MAPK 途径了解 RTK 信号传导与 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 的信号传导与 ER 输出机制连接起来。该模型预测，在 CLSD 中，SEC23A 缺陷会导致 RTK 运输效率低下，从而导致 MAPK 信号传导减少，而在 CS 中，FGFR-MAPK 信号传导增强会导致 ER 输出过度增加。为了测试这些预测，我们将测试 SEC23A 缺陷是否会阻止 RTK 的 ER 输出并影响 MAPK 信号传导（CLSD 案例），并且我们将测试过度活跃的 FGFR-MAPK 信号传导是否会导致 COPII 囊泡过度组装（CS 案例）。