Steric-Deficient Oligoglycine Surrogates Facilitate Multivalent and Bifunctional Nanobody Synthesis via Combined Sortase A Transpeptidation and Click Chemistry

Conferring multifunctional properties to proteins via enzymatic approaches has greatly facilitated recent progress in protein nanotechnology. In this regard, sortase (Srt) A transpeptidation has facilitated many of these developments due to its exceptional specificity, mild reaction conditions, and complementation with other bioorthogonal techniques, such as click chemistry. In most of these developments, Srt A is used to seamlessly tether oligoglycine-containing molecules to a protein of interest that is equipped with the enzyme's recognition sequence, LPXTG. However, the dependence on oligoglycine attacking nucleophiles and the associated cost of certain derivatives (e.g., cyclooctyne) limit the utility of this approach to lab-scale applications only. Thus, the quest to identify appropriate alternatives and understand their effectiveness remains an important area of research. This study identifies that steric and nucleophilicity-associated effects influence Srt A transpeptidation when two oligoglycine surrogates were examined. The approach was further used in complementation with click chemistry to synthesize bivalent and bifunctional nanobody conjugates for application in epithelial growth factor receptor targeting. The overall technique and tools developed here may facilitate the advancement of future nanotechnologies.

Rapid whole cell imaging reveals a calcium-APPL1-dynein nexus that regulates cohort trafficking of stimulated EGF receptors

The endosomal system provides rich signal processing capabilities for responses elicited by growth factor receptors and their ligands. At the single cell level, endosomal trafficking becomes a critical component of signal processing, as exemplified by the epidermal growth factor (EGF) receptors. Activated EGFRs are trafficked to the phosphatase-enriched peri-nuclear region (PNR), where they are dephosphorylated and degraded. The details of the mechanisms that govern the movements of stimulated EGFRs towards the PNR, are not completely known. Here, exploiting the advantages of lattice light-sheet microscopy, we show that EGFR activation by EGF triggers a transient calcium increase causing a whole-cell level redistribution of Adaptor Protein, Phosphotyrosine Interacting with PH Domain And Leucine Zipper 1 (APPL1) from pre-existing endosomes within one minute, the rebinding of liberated APPL1 directly to EGFR, and the dynein-dependent translocation of APPL1-EGF-bearing endosomes to the PNR within ten minutes. The cell spanning, fast acting network that we reveal integrates a cascade of events dedicated to the cohort movement of activated EGF receptors. Our findings support the intriguing proposal that certain endosomal pathways have shed some of the stochastic strategies of traditional trafficking and have evolved processes that provide the temporal predictability that typify canonical signaling.

Human Plasminogen Exacerbates Clostridioides difficile Enteric Disease and Alters the Spore Surface

BACKGROUND & AIMS

The protease plasmin is an important wound healing factor, but it is not clear how it affects gastrointestinal infection-mediated damage, such as that resulting from Clostridioides difficile. We investigated the role of plasmin in C difficile-associated disease. This bacterium produces a spore form that is required for infection, so we also investigated the effects of plasmin on spores.

METHODS

C57BL/6J mice expressing the precursor to plasmin, the zymogen human plasminogen (hPLG), or infused with hPLG were infected with C difficile, and disease progression was monitored. Gut tissues were collected, and cytokine production and tissue damage were analyzed by using proteomic and cytokine arrays. Antibodies that inhibit either hPLG activation or plasmin activity were developed and structurally characterized, and their effects were tested in mice. Spores were isolated from infected patients or mice and visualized using super-resolution microscopy; the functional consequences of hPLG binding to spores were determined.

RESULTS

hPLG localized to the toxin-damaged gut, resulting in immune dysregulation with an increased abundance of cytokines (such as interleukin [IL] 1A, IL1B, IL3, IL10, IL12B, MCP1, MP1A, MP1B, GCSF, GMCSF, KC, TIMP-1), tissue degradation, and reduced survival. Administration of antibodies that inhibit plasminogen activation reduced disease severity in mice. C difficile spores bound specifically to hPLG and active plasmin degraded their surface, facilitating rapid germination.

CONCLUSIONS

We found that hPLG is recruited to the damaged gut, exacerbating C difficile disease in mice. hPLG binds to C difficile spores, and, upon activation to plasmin, remodels the spore surface, facilitating rapid spore germination. Inhibitors of plasminogen activation might be developed for treatment of C difficile or other infection-mediated gastrointestinal diseases.

Adhesion G-protein-coupled receptor, GPR56, is required for Müllerian duct development in the chick

The embryonic Müllerian ducts give rise to the female reproductive tract (fallopian tubes, uterus and upper vagina in humans, the oviducts in birds). Embryonic Müllerian ducts initially develop in both sexes, but later regress in males under the influence of anti-Müllerian hormone. While the molecular and endocrine control of duct regression in males have been well studied, early development of the ducts in both sexes is less well understood. Here, we describe a novel role for the adhesion G protein-coupled receptor, GPR56, in development of the Müllerian ducts in the chicken embryo. GPR56 is expressed in the ducts of both sexes from early stages. The mRNA is present during the elongation phase of duct formation, and it is restricted to the inner Müllerian duct epithelium. The putative ligand, Collagen III, is abundantly expressed in the Müllerian duct at the same developmental stages. Knockdown of GPR56 expression using in ovo electroporation results in variably truncated ducts, with a loss of expression of both epithelial and mesenchymal markers of duct development. Over-expression of GPR56 in vitro results in enhanced cell proliferation and cell migration. These results show that GPR56 plays an essential role in avian Müllerian duct development through the regulation of duct elongation.

Non-resective ablation and liver transplantation in patients with cirrhosis and hepatocellular carcinoma (HCC): safety and efficacy

We investigated the efficacy of nonresective ablation techniques and the tumor-free survival of cirrhotic patients undergoing liver transplantation for hepatocellular carcinoma (HCC). In group 1, 11 HCC patients were treated with these techniques and transplanted. On the waiting list, patients were treated to complete ablation, judged by gadolinium-enhanced MRI and alpha-fetoprotein (AFP) levels. Group 1 was compared with a concurrent group of 10 liver transplant patients (group 2) with incidental HCC (stages T1 three patients, T2 seven patients). The group 1 patients received 36 procedures (4 alcohol ablations, 14 trans -hepatic artery chemo-embolizations, 15 trans -hepatic chemo-infusions, and 3 radio frequency ablations) for treatment of 13 liver masses. Tumor-node-metastasis (TNM) stage was reduced in eight patients (72.7%), unchanged in two patients and increased in one patient before transplantation. The mean waiting time for transplantation was 12.9 7.6 months. Both groups had a tumor-free survival of 100%, at 30 12 months post transplant. On pathology, 54.5% of explanted livers had residual viable HCC after tumor treatment, and 36.4% (4/11) explants had synchronous lesions. Non-resective ablation therapy is safe and effective in reducing the HCC progression in cirrhotic patients awaiting liver transplantation. The cancer-free survival rate in this treatment group is equal to that for incidental T1-T2 HCCs.

Aneurysms of the portal vein and superior mesenteric vein

Only scattered reports of portal vein and superior mesenteric vein aneurysms appear in the literature. Case reports of three patients with portal vein and superior mesenteric vein aneurysms diagnosed by computed tomography (CT) and gray-scale, color Doppler, and duplex Doppler sonography are presented. In one case, an isolated portal vein aneurysm was demonstrated. In the second case, an aneurysm of the portal vein and superior mesenteric vein resulting in biliary ductal dilatation was observed. In the third case, an isolated superior mesenteric vein aneurysm was found. None of the patients had a history or clinical evidence of underlying liver disease, pancreatitis, or other disease states that would predispose them to the development of aneurysms. The clinical presentations, possible etiologies, and imaging features of portal vein and superior mesenteric vein aneurysms are reviewed. The value of CT and sonography in the detection and characterization of these rare aneurysms is discussed.