Recognition Of HIV Envelope gp120 by Siglec and C-type Lectin Receptors

Siglec 和 C 型凝集素受体对 HIV 包膜 gp120 的识别

• 批准号: 8745382
• 负责人: PETER D. SUN
• 金额: $ 52.38万
• 依托单位: NATIONAL INSTITUTE OF ALLERGY AND INFECTIOUS DISEASES
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8745382
• 关键词: Adhesions; Affinity; Antibody Affinity; Antigen Presentation; Antigens; Binding; Biological Assay; C Type Lectin Receptors; CD209 gene; CD4 Positive T Lymphocytes; Cancer cell line; Carbohydrates; Cattle; Cell Adhesion Molecules; Cell surface; Cells; Colo205; Complex; Confocal Microscopy; Data; Dendritic Cells; Dose; Extracellular Matrix Proteins; Family; Genome; Glycoproteins; HIV; HIV Envelope Protein gp120; HIV Infections; HIV-1; Human Genome; Human Virus; Infection; Intercellular Adhesion Molecule 2; Lead; Lectin; Ligand Binding Domain; Ligands; Lymphocyte antigen CD50; Mannans; Modeling; Molecular; Molecular Conformation; Molecular Models; Mucin-1 Staining Method; Mucins; N-terminal; Oligosaccharides; Pathogenesis; Phase; Physiological; Protein Family; Proteins; RNA Viruses; Receptor Signaling; Recombinant Proteins; Resolution; Roentgen Rays; Role; SELL gene; Scheme; Sialic Acids; Solutions; Specificity; Structure; T-Cell Activation; T-Lymphocyte; Translations; Tumor Markers; Viral; base; biphenyl hydrolase-related protein; carbohydrate receptor; disulfide bond; env Gene Products; extracellular; human SIGLEC5 protein; insight; member; molecular modeling; receptor; receptor binding; receptor internalization; research study; sialic acid binding Ig-like lectin; transmission process; tumor

DC-SIGN, a dendritic cell surface C-type lectin receptor, has been proposed to enhance HIV-1 infection of T cells in trans. The physiological role of DC-SIGN was thought to bind adhesion molecules, ICAM-2 and ICAM-3, to initiate a dendritic cell and T cell contact to facilitate the T cell activation and priming by dendritic cells. We expressed various extracellular truncations of DC-SIGN and DC-SIGNR as recombinant proteins and showed that 1) DC-SIGN/R forms a tetramer through the extracellular repeat region; 2) the receptor-gp120 binding affinity depends on the oligomerization of the receptor; 3) DC-SIGN/R recognition of gp120 is pH dependent such that the affinity reduced drastically under the endosomal pH condition; and 4) DC-SIGN recognizes ICAM-3 with much lower affinity than it does gp120. The structural study of DC-SIGN/R has resulted in a 1.5 E resolution crystal structure for DC-SIGN R8 and a molecular model for the tetrameric extracellular DC-SIGN/R. Based on the model, a prediction scheme was developed to evaluate potential ligands for DC-SIGN. A ligand search among the sequences of the human genome and genomes of human viruses revealed a diverse list of potential host and viral ligands of the receptor. The host ligands include not only adhesion molecules but also a family of mucin-like proteins, the extracellular matrix proteins and some tumor markers. Most of the enveloped RNA viruses appear to have ligands for the receptor. Using a bovine submaxillary mucin as the example, we showed both in solution and on the cell surface that DC-SIGN and DC-SIGNR recognize the mucin family of proteins with sub-micromolar affinity. The receptor binding to mucin competes with the receptor binding to HIV-1 gp120. Using FACS analysis and confocal microscopy, we showed that DC-SIGN preferentially recognizes MUC1-transfected cells as well as an MUC1-expressing cancer cell line Colo205. The binding of DC-SIGN/R to Colo205 cells can be blocked with mannan in a dose-dependent manner. Thus, we propose that DC-SIGN functions as an antigen- capturing receptor for both viral glycoprotein and cellular tumor and mucin-associated antigens. The receptor internalization would lead to the degradation and antigen presentation. SIGLECs (sialic-acid Ig-like binding lectins) are a family of adhesion and signaling receptors that specifically recognize sialylated carbohydrate moieties. The potential involvement of members of SIGLEC family receptors in HIV pathogenesis remain to be determined. To understand the molecular basis for the sialic acid-dependent adhesion implemented by SIGLECs and to get an insight into receptor specificity, structural studies have been carried out using two Ig-like N-terminal domains of SIGLEC-5. X-ray structure solution using molecular replacement with phased translation function uncovered unparalleled features not seen in other one-domain structures of related SIGLECs, including unusual conformation of variable loop C-C of the ligand-binding domain and a unique interdomain disulfide bond. To get an insight into receptor specificity, we have crystallized several receptor-ligand complexes using sialylated oligosaccharides commonly found at cell surfaces and in the extracellular milieu. In combination with binding assays, these structural studies have given us an insight into what governs ligand recognition and receptor specificity in SIGLEC family of lectins. In addition to Siglec receptors, we recently began to investigate the potential interaction between C-type lectin receptor, CD62L, and HIV-1 envelope protein gp120. Our preliminary data showed that gp120 binds CD62L with nM affinity and antibody against CD62L inhibited HIV-1 infection of CD4 T cells.

DC-SIGN是一种树突状细胞表面C型凝集素受体，已提出增强反式T细胞的HIV-1感染。 DC-SIGN的生理作用被认为是结合粘附分子ICAM-2和ICAM-3，以启动树突状细胞和T细胞接触，以促进T细胞的激活和树突状细胞的启动。 我们表达了DC-SIGN和DC-SIGNR作为重组蛋白的各种细胞外截断，并表明1）DC-SIGN/R通过细胞外重复区域形成四聚体； 2）受体-GP120结合亲和力取决于受体的寡聚化； 3）DC-SIGN/R识别GP120的pH值依赖性，因此亲和力在内体pH条件下大幅降低； 4）DC-SIGN识别ICAM-3的亲和力远低于GP120。 DC-SIGN/R的结构研究导致DC-SIGN R8的1.5 E分辨率晶体结构和四聚体外DC-SIGN/R的分子模型。 基于该模型，开发了一种预测方案来评估DC-SIGN的潜在配体。 在人类基因组和人类病毒基因组序列之间进行的配体搜索揭示了受体的潜在宿主和病毒配体的各种列表。 宿主配体不仅包括粘附分子，还包括粘蛋白样蛋白，细胞外基质蛋白和一些肿瘤标记的家族。 大多数包围的RNA病毒似乎具有用于受体的配体。 我们以牛超X.粘蛋白为例，我们在溶液和细胞表面上均显示了DC-SIGN和DC-SIGNR识别具有亚微摩尔亲和性的蛋白质的粘蛋白家族。 与粘蛋白结合的受体与与HIV-1 GP120的受体结合竞争。 使用FACS分析和共聚焦显微镜，我们表明DC符号优先识别了MUC1转染的细胞以及表达MUC1的癌细胞系Colo205。 DC-SIGN/R与Colo205细胞的结合可以用剂量依赖性方式阻止。因此，我们提出DC-SIGN充当病毒糖蛋白和细胞肿瘤和粘蛋白相关抗原的抗原捕获受体。 受体内在化将导致降解和抗原表现。 Siglecs（唾液酸Ig样结合凝集素）是一个粘附和信号受体家族，专门识别硫化碳水化合物部分。 SIGLEC家族受体成员参与HIV发病机理的潜在参与尚待确定。 为了了解Siglecs实现的唾液酸依赖性粘附的分子基础并深入了解受体特异性，已经使用SIGLEC-5的两个Ig样的N末端结构域进行了结构研究。 X射线结构溶液使用分子替换和阶梯平移函数发现了相关Siglecs的其他一域结构中未见的无与伦比的特征，包括配体结合域的可变环C-C的异常构象和独特的间二硫化二硫化物键。为了深入了解受体特异性，我们使用通常在细胞表面和细胞外环境中发现的硫化寡糖结晶了几种受体配体复合物。结合结合测定，这些结构性研究使我们深入了解了在Siglec凝集素家族中的配体识别和受体特异性的原因。 除Siglec受体外，我们最近开始研究C型凝集素受体，CD62L和HIV-1 Invelope蛋白GP120之间的潜在相互作用。 我们的初步数据表明，GP120与NM亲和力结合CD62L和抗体与CD62L抑制CD4 T细胞的HIV-1感染。