MPP5 binds SARS-CoV-2 E pentamer

This SARS-CoV-2 event was manually inferred from the interaction of homologous SARS-CoV-1 E protein with human MAGUK p55 subfamily member 5 (MPP5, also known as PALS1).<p>MPP5 (PALS1), a tight junction-associated protein, is a member of the CRUMBS3:MPP5:PATJ polarity complex, which is crucial for the establishment and maintenance of epithelial polarity in mammals. MPP5 has multiple protein-protein interaction domains including a PSD-95/Dlg/ZO-1 (PDZ) domain. A functional PDZ domain-binding motif has been identified at the carboxy-terminus end of SARS-CoV-1 E (Teoh KT et al. 2010; Jimenez-Guardeño JM et al. 2014) and SARS-CoV-2 E (Caillet-Saguy C et al. 2021; Chai J et al. 2021; Shepley-McTaggart A et al. 2021). SARS-CoV-2 E and SARS-CoV-1 E are abundantly expressed inside the infected cell and actively involved in the pathogenic viral mechanisms (Venkatagopalan P et al. 2015; Wong NA & Saier MH Jr 2021). The viral E localizes to the endoplasmic reticulum-Golgi intermediate compartment (ERGIC) for viral assembly and budding. NMR spectroscopy identified the pentameric structure of transmembrane domain of SARS‐CoV‐2 E protein in lipid bilayers (Mandala VS et al. 2020). Infection with recombinant SARS-CoV-1 lacking an E protein PDZ domain-binding motif was attenuated in mice, which was accompanied by a decreased expression of inflammatory cytokines during infection, and a substantial increase of survival (Jimenez-Guardeño JM et al. 2014). SARS-CoV-1 E was found to interfere with host PDZ‐dependent interactions of MPP5 affecting cellular mechanisms thus favoring viral replication (Teoh KT et al. 2010). Coimmunoprecipitation and pull-down assays showed that the viral E protein interacted with MPP5 in human embryonic kidney 293T (HEK293T) and African green monkey kidney Vero E6 cells (Teoh KT et al. 2010). The last four carboxy-terminal amino acids (DLLV) of E interacted with the PDZ domain of MPP5 (Teoh KT et al. 2010). Immunofluorescence assay showed that MPP5 was mainly localized at cell-cell junctions in monolayers of non infected Vero E6 cells, while the binding of SARS-CoV-1 E to MPP5 (PALS1) redistributed MPP5 from the tight junctions of the lung epithelium to the ER-Golgi intermediate compartment (ERGIC) where E assembles in SARS-CoV-1-infected Vero E6 cells (Teoh KT et al. 2010). Ectopic expression of E in madin-darby canine kidney II (MDCKII) epithelial cells significantly altered cyst morphogenesis and, furthermore, delayed formation of tight junctions, affected polarity, and modifies the subcellular distribution of MPP5, in a PDZ-binding motif-dependent manner (Teoh KT et al. 2010). Altogether, these findings suggest that SARS-CoV-1 E interacts with MPP5 (PALS1) and most likely retains MPP5 at the virus assembly site in mammalian cells. However, the relevance of this interaction during virus infection and its impact on virulence in vivo was not tested.<p>A sequence comparison of the E proteins of the pathogenic human CoVs, SARS-CoV-1, MERS-CoV, and SARS-CoV-2, demonstrated a very high sequence similarity between SARS-CoV-1 E and SARS-CoV-2 E (Grifoni A et al. 2020; Schoeman D & Fielding BC 2020; Hassan SS et al. 2020). This similarity is not shared with the MERS-CoV E protein (Schoeman D & Fielding BC 2020). In silico structural modelling and analyses of E proteins suggested a strengthened binding of SARS-CoV-2 E protein with MPP5 (De Maio F et al. 2020). Equilibrium and kinetic binding experiments of peptides mimicking the E protein of SARS-CoV-1 and SARS-CoV-2 to the PDZ domain of MPP5 further support the hypothesis that the increased virulence of SARS-CoV-2 compared to SARS-CoV-1 may rely on the increased affinity of its E protein for MPP5 (Toto A et al. 2020). However, these binding affinity measurements (Toto A et al. 2020) differ from the findings that the C-terminal PDZ binding motifs of SARS-CoV-1 and SARS-CoV-2 E proteins bind the MPP5 PDZ domain with comparable affinities (Javorsky A et al. 2021). Further, structural studies of the SARS-CoV-2 E:MPP5 complex revealed that the C-terminal DLLV motif of E recognizes a pocket formed by hydrophobic residues from the PDZ and SH3 domains of MPP5 (PALS1) (Chai J et al. 2021; Javorsky A et al. 2021). Similar structural data were reported for the SARS-CoV-1 E protein (Javorsky A et al. 2021).<p>This Reactome event shows interaction between SARS-CoV-2 E pentamer and human MPP5.

此SARS-CoV-2事件系通过手动推断同源SARS-CoV-1 E蛋白与人类MAGUK p55亚家族成员5（MPP5，亦称PALS1）的相互作用而得出。<p>MPP5（PALS1），一种紧密连接相关蛋白，是CRUMBS3:MPP5:PATJ极性复合体的一员，该复合体对于哺乳动物上皮极性的建立与维持至关重要。MPP5具有多个蛋白-蛋白相互作用结构域，包括PSD-95/Dlg/ZO-1（PDZ）结构域。在SARS-CoV-1 E（Teoh KT 等人，2010年）和SARS-CoV-2 E（Caillet-Saguy C 等人，2021年；Chai J 等人，2021年；Shepley-McTaggart A 等人，2021年）的羧基末端已鉴定出一种功能性的PDZ结合基序。SARS-CoV-2 E和SARS-CoV-1 E在感染细胞内大量表达，并积极参与致病性病毒机制（Venkatagopalan P 等人，2015年；Wong NA & Saier MH Jr，2021年）。病毒E蛋白定位于内质网-高尔基体中间区域（ERGIC）以进行病毒组装和芽生。核磁共振光谱识别了SARS-CoV-2 E蛋白跨膜结构域在脂质双分子层中的五聚体结构（Mandala VS 等人，2020年）。感染缺失E蛋白PDZ结合基序的重组SARS-CoV-1在小鼠中的致病性减弱，伴随感染期间炎症细胞因子表达降低，存活率显著提高（Jimenez-Guardeño JM 等人，2014年）。研究发现SARS-CoV-1 E蛋白与宿主PDZ依赖性相互作用影响MPP5的细胞机制，从而有利于病毒复制（Teoh KT 等人，2010年）。共免疫沉淀和下拉实验表明，病毒E蛋白与人类胚胎肾293T（HEK293T）细胞和非洲绿猴肾Vero E6细胞中的MPP5相互作用（Teoh KT 等人，2010年）。E蛋白的末四个羧基末端氨基酸（DLLV）与MPP5的PDZ结构域相互作用（Teoh KT 等人，2010年）。免疫荧光实验显示，MPP5主要定位于未感染Vero E6细胞层间的细胞连接处，而SARS-CoV-1 E与MPP5（PALS1）的结合则将MPP5从肺上皮的紧密连接处转移至E在SARS-CoV-1感染Vero E6细胞中组装的内质网-高尔基体中间区域（ERGIC）。在犬肾上皮细胞MDCKII中过表达E蛋白显著改变了囊肿形态发生，进一步地，延迟了紧密连接的形成，影响了极性，并以PDZ结合基序依赖的方式改变了MPP5的亚细胞分布（Teoh KT 等人，2010年）。总之，这些发现表明SARS-CoV-1 E与MPP5（PALS1）相互作用，且很可能在哺乳动物细胞中将MPP5保留在病毒组装位点。然而，这种相互作用在病毒感染过程中的相关性及其对体内致病性的影响尚未得到测试。<p>对致病性人类冠状病毒SARS-CoV-1、MERS-CoV和SARS-CoV-2的E蛋白序列进行比较，发现SARS-CoV-1 E与SARS-CoV-2 E之间具有极高的序列相似性（Grifoni A 等人，2020年；Schoeman D & Fielding BC，2020年；Hassan SS 等人，2020年）。这种相似性并未与MERS-CoV E蛋白共享（Schoeman D & Fielding BC，2020年）。对E蛋白进行计算机辅助的结构建模和分析表明，SARS-CoV-2 E蛋白与MPP5的结合能力增强（De Maio F 等人，2020年）。模拟SARS-CoV-1和SARS-CoV-2 E蛋白的肽段与MPP5 PDZ结构域的平衡和动力学结合实验进一步支持了假设，即与SARS-CoV-1相比，SARS-CoV-2的病毒致病性增加可能依赖于其E蛋白对MPP5的亲和力增加（Toto A 等人，2020年）。然而，这些结合亲和力测量结果（Toto A 等人，2020年）与SARS-CoV-1和SARS-CoV-2 E蛋白的羧基末端PDZ结合基序与MPP5 PDZ结构域以相似亲和力结合的发现不同（Javorsky A 等人，2021年）。此外，SARS-CoV-2 E:MPP5复合物的结构研究揭示了E蛋白的羧基末端DLLV基序识别由MPP5（PALS1）的PDZ和SH3结构域形成的疏水性残基形成的口袋（Chai J 等人，2021年；Javorsky A 等人，2021年）。类似的结构数据也报道了SARS-CoV-1 E蛋白（Javorsky A 等人，2021年）。<p>本Reactome事件展示了SARS-CoV-2 E五聚体与人类MPP5之间的相互作用。