Chemical labelling of active serum thioester proteins for quantification

Protein therapeutics and their lessons: Expect the unexpected when inhibiting the multi-protein cascade of the complement system

Over a century after the discovery of the complement system, the first complement therapeutic was approved for the treatment of paroxysmal nocturnal hemoglobinuria (PNH). It was a long-acting monoclonal antibody (aka 5G1-1, 5G1.1, h5G1.1, and now known as eculizumab) that targets C5, specifically preventing the generation of C5a, a potent anaphylatoxin, and C5b, the first step in the eventual formation of membrane attack complex. The enormous clinical and financial success of eculizumab across four diseases (PNH, atypical hemolytic uremic syndrome (aHUS), myasthenia gravis (MG), and anti-aquaporin-4 (AQP4) antibody-positive neuromyelitis optica spectrum disorder (NMOSD)) has fueled a surge in complement therapeutics, especially targeting diseases with an underlying complement pathophysiology for which anti-C5 therapy is ineffective. Intensive research has also uncovered challenges that arise from C5 blockade. For example, PNH patients can still face extravascular hemolysis or pharmacodynamic breakthrough of complement suppression during complement-amplifying conditions. These "side" effects of a stoichiometric inhibitor like eculizumab were unexpected and are incompatible with some of our accepted knowledge of the complement cascade. And they are not unique to C5 inhibition. Indeed, "exceptions" to the rules of complement biology abound and have led to unprecedented and surprising insights. In this review, we will describe initial, present and future aspects of protein inhibitors of the complement cascade, highlighting unexpected findings that are redefining some of the mechanistic foundations upon which the complement cascade is organized.

LncRNA RP11-116G8.5 promotes the progression of lung squamous cell carcinoma through sponging miR-3150b-3p/miR-6870-5p to upregulate PHF12/FOXP4

BACKGROUND

Lung squamous cell carcinoma (LUSC) is one of the commonest malignancies worldwide. Long noncoding RNAs (lncRNAs) have been revealed to engage in cancer development. LncRNA RP11-116G8.5 is a new founded lncRNA that has not been clearly elucidated in LUSC.

MATERIALS AND METHODS

Expression levels of RNAs in LUSC cells were measured through qRT-PCR. To identify the functions of RP11-116G8.5, CCK-8 assay, colony formation assay and EdU assay were conducted in indicated LUSC cells. Mechanism experiments, including RNA pull down assay, Ago2-RIP assay and luciferase reporter assay were performed to demonstrate the interaction between RP11-116G8.5 and miR-3150b-3p/miR-6870-5p. Meanwhile, the interaction between miR-3150b-3p/miR-6870-5p and their downstream targets PHD finger protein 12 (PHF12), and forkhead box P4 (FOXP4) were also proven in the same methods.

RESULTS

RP11-116G8.5 was expressed at high level in LUSC cell lines. Down-regulated RP11-116G8.5 repressed cell proliferation, migration and invasion, but accelerated apoptosis. Furthermore, it was proven that RP11-116G8.5 could act as sponges for miR-3150b-3p and miR-6870-5p these miRNAs were found to act as cancer suppressors in LUSC cells. PHF12 and FOXP4 were verified as the target gene of miR-3150b-3p and miR-6870-5p separately. Overexpression of PHF12 and FOXP4 could reverse the repressive effect of RP11-116G8.5 knockdown on LUSC progression. Additionally, Paired Box 5 (PAX-5) was proven to be the transcription factor for RP11-116G8.5 in LUSC cells.

CONCLUSIONS

LncRNA RP11-116G8.5 promotes malignant behaviors of LUSC through sponging miR-3150b-3p/miR-6870-5p to upregulate PHF12/FOXP4 expression.

AVAILABILITY OF DATA

The research data is confidential.

The Carbohydrate-linked Phosphorylcholine of the Parasitic Nematode Product ES-62 Modulates Complement Activation

Parasitic nematodes manufacture various carbohydrate-linked phosphorylcholine (PCh)-containing molecules, including ES-62, a protein with an N-linked glycan terminally substituted with PCh. The PCh component is biologically important because it is required for immunomodulatory effects. We showed that most ES-62 was bound to a single protein, C-reactive protein (CRP), in normal human serum, displaying a calcium-dependent, high-avidity interaction and ability to form large complexes. Unexpectedly, CRP binding to ES-62 failed to efficiently activate complement as far as the C3 convertase stage in comparison with PCh-BSA and PCh-containing Streptococcus pneumoniae cell wall polysaccharide. C1q capture assays demonstrated an ES-62-CRP-C1q interaction in serum. The three ligands all activated C1 and generated C4b to similar extents. However, a C2a active site was not generated following ES-62 binding to CRP, demonstrating that C2 cleavage was far less efficient for ES-62-containing complexes. We proposed that failure of C2 cleavage was due to the flexible nature of carbohydrate-bound PCh and that reduced proximity of the C1 complex was the reason that C2 was poorly cleaved. This was confirmed using synthetic analogues that were similar to ES-62 only in respect of having a flexible PCh. Furthermore, ES-62 was shown to deplete early complement components, such as the rate-limiting C4, following CRP interaction and thereby inhibit classical pathway activation. Thus, flexible PCh-glycan represents a novel mechanism for subversion of complement activation. These data illustrate the importance of the rate-limiting C4/C2 stage of complement activation and reveal a new addition to the repertoire of ES-62 immunomodulatory mechanisms with possible therapeutic applications.

Studying weak and dynamic interactions of posttranslationally modified proteins using expressed protein ligation

Many cellular processes are regulated by posttranslational modifications that are recognized by specific domains in protein binding partners. These interactions are often weak, thus allowing a highly dynamic and combinatorial regulatory network of protein-protein interactions. We report an efficient strategy that overcomes challenges in structural analysis of such a weak transient interaction between the Tudor domain of the Survival of Motor Neuron (SMN) protein and symmetrically dimethylated arginine (sDMA). The posttranslational modification is chemically introduced and covalently linked to the effector module by a one-pot expressed protein ligation (EPL) procedure also enabling segmental incorporation of NMR-active isotopes for structural analysis. Covalent coupling of the two interacting moieties shifts the equilibrium to the bound state, and stoichiometric interactions are formed even for low affinity interactions. Our approach should enable the structural analysis of weak interactions by NMR or X-ray crystallography to better understand the role of posttranslational modifications in dynamic biological processes.