Genetics and mechanisms of hepatic cystogenesis

Polycystic liver disease (PLD) is a heterogeneous genetic condition. PKD1 and PKD2 germline mutations are found in patients with autosomal dominant polycystic kidney disease (ADPKD). Autosomal dominant polycystic liver disease (ADPLD) is associated with germline mutations in PRKCSH, SEC63, LRP5, and recently ALG8 and SEC61. GANAB mutations are found in both patient groups. Loss of heterozygosity of PLD-genes in cyst epithelium contributes to the development of hepatic cysts. A genetic interaction network is implied in hepatic cystogenesis that connects the endoplasmic glycoprotein control mechanisms and polycystin expression and localization. Wnt signalling could be the major downstream signalling pathway that results in hepatic cyst growth. PLD in ADPLD and ADPKD probably results from changes in one common final pathway that initiates cyst growth. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.     

CD47分子与抗肿瘤免疫

肿瘤进展与人免疫系统间的联系已经被广泛研究,有许多免疫分子已被证实参与其中。CD47（整合素相关蛋白）为一种免疫球蛋白超家族成员,在人免疫系统中发挥着重要功能。研究表明CD47在肿瘤细胞表面也有高表达,其高表达与肿瘤的生长、转移及复发等密切相关。肿瘤细胞表面的CD47与巨噬细胞表面的SIRPα相互作用,并发出“别吃我”的免疫抑制性信号,从而保护肿瘤细胞免受巨噬细胞吞噬。因此,开发以CD47为靶点的拮抗剂可阻断此抑制性信号,从而增强巨噬细胞的吞噬效应,以达到增强抗肿瘤免疫反应的目的。最新研究证实,CD47拮抗剂在T细胞介导的抗肿瘤免疫反应中也发挥了重要作用。本文将对CD47分子的结构功能、在抗肿瘤免疫反应中的作用及以其为靶点的拮抗剂研究进展进行综述,以期为进一步的药物开发及临床研究等提供参考。     

Brain Shuttle Antibody for Alzheimer’s Disease with Attenuated Peripheral Effector Function due to an Inverted Binding Mode

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Extending human IgG half-life using structure-guided design

Engineering of antibodies for improved pharmacokinetics through enhanced binding to the neonatal Fc receptor (FcRn) has been demonstrated in transgenic mice, non-human primates and humans. Traditionally, such approaches have largely relied on random mutagenesis and display formats, which fail to address related critical attributes of the antibody, such as effector functions or biophysical stability. We have developed a structure- and network-based framework to interrogate the engagement of IgG with multiple Fc receptors (FcRn, C1q, TRIM21, FcγRI, FcγRIIa/b, FcγRIIIa) simultaneously. Using this framework, we identified features that govern Fc-FcRn interactions and identified multiple distinct pathways for enhancing FcRn binding in a pH-specific manner. Network analysis provided a novel lens to study the allosteric impact of half-life-enhancing Fc mutations on FcγR engagement, which occurs distal to the FcRn binding site. Applying these principles, we engineered a panel of unique Fc variants that enhance FcRn binding while maintaining robust biophysical properties and wild type-like binding to activating receptors. An antibody harboring representative Fc designs demonstrates a half-life improvement of > 9 fold in transgenic mice and > 3.5 fold in cynomolgus monkeys, and maintains robust effector functions such as antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity.     

Wheat PR‐1 proteins are targeted by necrotrophic pathogen effector proteins

Recent studies have identified that proteinaceous effectors secreted by Parastagonospora nodorum are required to cause disease on wheat. These effectors interact in a gene‐for‐gene manner with host‐dominant susceptibilty loci, resulting in disease. However, whilst the requirement of these effectors for infection is clear, their mechanisms of action remain poorly understood. A yeast‐two‐hybrid library approach was used to search for wheat proteins that interacted with the necrotrophic effector SnTox3. Using this strategy we indentified an interaction between SnTox3 and the wheat pathogenicity‐related protein TaPR‐1‐1, and confirmed it by in‐planta co‐immunprecipitation. PR‐1 proteins represent a large family (23 in wheat) of proteins that are upregulated early in the defence response; however, their function remains ellusive. Interestingly, the P. nodorum effector SnToxA has recently been shown to interact specifically with TaPR‐1‐5. Our analysis of the SnTox3–TaPR‐1 interaction demonstrated that SnTox3 can interact with a broader range of TaPR‐1 proteins. Based on these data we utilised homology modeling to predict, and validate, regions on TaPR‐1 proteins that are likely to be involved in the SnTox3 interaction. Precipitating from this work, we identified that a PR‐1‐derived defence signalling peptide from the C‐terminus of TaPR‐1‐1, known as CAPE1, enhanced the infection of wheat by P. nodorum in an SnTox3‐dependent manner, but played no role in ToxA‐mediated disease. Collectively, our data suggest that P. nodorum has evolved unique effectors that target a common host‐protein involved in host defence, albeit with different mechanisms and potentially outcomes.     

Identification of pathogenicity‐related genes in Fusarium oxysporum f. sp. cepae

Pathogenic isolates of Fusarium oxysporum, distinguished as formae speciales (f. spp.) on the basis of their host specificity, cause crown rots, root rots and vascular wilts on many important crops worldwide. Fusarium oxysporum f. sp. cepae (FOC) is particularly problematic to onion growers worldwide and is increasing in prevalence in the UK. We characterized 31 F. oxysporum isolates collected from UK onions using pathogenicity tests, sequencing of housekeeping genes and identification of effectors. In onion seedling and bulb tests, 21 isolates were pathogenic and 10 were non‐pathogenic. The molecular characterization of these isolates, and 21 additional isolates comprising other f. spp. and different Fusarium species, was carried out by sequencing three housekeeping genes. A concatenated tree separated the F. oxysporum isolates into six clades, but did not distinguish between pathogenic and non‐pathogenic isolates. Ten putative effectors were identified within FOC, including seven Secreted In Xylem (SIX) genes first reported in F. oxysporum f. sp. lycopersici. Two highly homologous proteins with signal peptides and RxLR motifs (CRX1/CRX2) and a gene with no previously characterized domains (C5) were also identified. The presence/absence of nine of these genes was strongly related to pathogenicity against onion and all were shown to be expressed in planta. Different SIX gene complements were identified in other f. spp., but none were identified in three other Fusarium species from onion. Although the FOC SIX genes had a high level of homology with other f. spp., there were clear differences in sequences which were unique to FOC, whereas CRX1 and C5 genes appear to be largely FOC specific.