Formins (FHOS) in CD21-mediated signaling & virus entry

CD21 介导的信号传导中的福尔明 (FHOS)

• 批准号: 6870631
• 负责人: JOYCE DIANE FINGEROTH
• 金额: $ 38.25万
• 依托单位: BETH ISRAEL DEACONESS MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2010-02-28
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6870631
• 关键词: CD19 molecule; Epstein Barr virus; actin binding protein; aminoacid; autoimmune disorder; binding proteins; biological signal transduction; human tissue; immunologic receptors; immunoregulation; infection; intermolecular interaction; laboratory rabbit; neoplasm /cancer; polymerization; protein structure function; receptor binding; receptor expression; virus infection mechanism

DESCRIPTION (provided by applicant): Human CD21 is an innate immune system receptor (C3dg receptor or complement receptor type 2, CR2) and is a key modulator of the acquired immune response. CD21 is also the high affinity receptor for EBV. CD21 plays a direct role in the pathogenesis of a broad spectrum of human disease, including autoimmune disease, infectious disease (EBV and HIV) and cancer. On B cells, CD21 complexes with the major signal transduction regulator CD19, and it is controversial whether CD21 can signal independently of CD19. Although CD21 was identified more than 20 years ago and distinct roles as an attachment protein for C3dg, CD23 and EBV have been discovered, the precise mechanisms enabling CD21 to directly relay information between the exterior and the interior of the cell are unresolved. In Preliminary Studies, FHOS/FHQD a member of the formin family, was found to bind the cytoplasmic domain of human CD21 both in vitro and in vivo. When expressed in epithelial cells (CD19 negative), EGFP-FHOS localized to the cytoplasm and accumulated with actin in membrane protrusions. Remarkably, when CD21 on epithelial cells was ligated with either EBV or anti-CD21, FHOS translocated to the plasma membrane, where it co-localized in aggregates with CD21. Formins are scaffolding proteins that regulate cell polarity and morphogenesis by linking signal transduction to cytoskeletal rearrangement and gene transcription. Recently, formins were discovered to directly nucleate actin by a pathway distinct from the classic Arp 2,3 complex. Based on these observations it is proposed that ligand stimulation of CD21-FHOS interaction transduces intracellular signals through a pathway directed by formin (FHOSV-mediated cytoskeletal reorganization). The goals of Aim I are to identify the amino acid residues that mediate interaction between CD21 and FHOS and to screen for novel FHOS/CD21-binding proteins as potential downstream effectors of this pathway. Aim II is focused on determining whether FHOS directly nucleates actin, and assessing the role of CD21 in FHOS activation, actin polymerization, and signaling. The goals of Aim III are to isolate and characterize the splenic littoral cell, a specialized cell abundant in human red pulp that highly expresses FHOS, CD21 and is believed to function in antigen filtration. Achievement of these Aims will provide important new knowledge about how CD21 signals and will elucidate the role(s) of the recently discovered formin protein, FHOS, in the immune system. These investigations may lead to identification of novel targets for treatment of autoimmune disease and cancer, for development of vaccines and for eradication of persistent viral and bacterial pathogens that are sequestered by CD21.

描述(申请人提供)：人CD21是一种先天性免疫系统受体(C3dg受体或补体受体2型，CR2)，是获得性免疫反应的关键调节器。CD21也是EBV的高亲和力受体。CD21在包括自身免疫性疾病、感染性疾病(EBV和HIV)和癌症在内的多种人类疾病的发病机制中发挥着直接作用。在B细胞上，CD21与主要的信号转导调节因子CD19形成复合体，CD21是否能独立于CD19发出信号尚存争议。虽然CD21早在20多年前就被发现，并且已经发现了CD21作为C3dg、CD23和EBV的不同附着蛋白的作用，但使CD21直接在细胞外部和内部之间传递信息的确切机制尚未解决。初步研究发现，FHOS/FHQD是Forin家族的一员，在体外和体内都能与人CD21的胞浆结构域结合。当在上皮细胞(CD19阴性)中表达时，EGFP-FHOS定位于细胞质，并与肌动蛋白一起聚集在膜突起中。值得注意的是，当上皮细胞上的CD21与EBV或抗CD21连接时，FHOS移位到质膜，在那里它与CD21共同定位在聚集体中。Formins是一种支架蛋白，通过将信号转导与细胞骨架重排和基因转录联系起来，调节细胞的极性和形态发生。最近，人们发现福尔马林通过一条不同于经典的Arp 2，3复合体的途径直接使肌动蛋白成核。基于这些观察结果，提出了CD21-FHOS相互作用的配体刺激通过Forin(FHOSV介导的细胞骨架重组)途径传递细胞内信号。目标I的目的是确定介导CD21和FHOS相互作用的氨基酸残基，并筛选新的FHOS/CD21结合蛋白作为这一途径的潜在下游效应蛋白。目的研究FHOS是否直接核化肌动蛋白，以及CD21在FHOS激活、肌动蛋白聚合和信号转导中的作用。AIM III的目标是分离和鉴定脾沿岸细胞，这是一种特殊的细胞，丰富地存在于人的红髓中，高表达FHOS和CD21，被认为具有抗原过滤功能。这些目标的实现将为CD21如何发出信号提供重要的新知识，并将阐明最近发现的形成蛋白FhoS在免疫系统中的作用(S)。这些研究可能导致确定治疗自身免疫性疾病和癌症的新靶点，开发疫苗，根除被CD21隔离的持久性病毒和细菌病原体。