Preclinical exploration of combined glucagon inhibition and liver-preferential insulin for treatment of diabetes using in vitro assays and rat and mouse models.

Aims/hypothesis: Normalisation of blood glucose in individuals with diabetes is recommended to reduce development of diabetic complications. However, risk of severe hypoglycaemia with intensive insulin therapy is a major obstacle that prevents many individuals with diabetes from obtaining the recommended reduction in HbA. Inhibition of glucagon receptor signalling and liver-preferential insulin action have been shown individually to have beneficial effects in preclinical models and individuals with diabetes (i.

Structural Investigations of Full-Length Insulin Receptor Dynamics and Signalling.

Insulin regulates glucose homeostasis via binding and activation of the insulin receptor dimer at two distinct pairs of binding sites 1 and 2. Here, we present cryo-EM studies of full-length human insulin receptor (hIR) in an active state obtained at non-saturating, physiologically relevant insulin conditions. Insulin binds asymmetrically to the receptor under these conditions, occupying up to three of the four possible binding sites.

Crystal structure and functional characterization of the complement regulator mannose-binding lectin (MBL)/ficolin-associated protein-1 (MAP-1).

The human lectin complement pathway activation molecules comprise mannose-binding lectin (MBL) and ficolin-1, -2, and -3 in complex with associated serine proteases MASP-1, -2, and -3 and the non-enzymatic small MBL associated protein or sMAP. Recently, a novel plasma protein named MBL/ficolin-associated protein-1 (MAP-1) was identified in humans. This protein is the result of a differential splicing of the MASP1 gene and includes the major part of the heavy chain but lacks the serine protease domain.

The interaction pattern of murine serum ficolin-A with microorganisms.

The ficolins are soluble pattern recognition molecules in the lectin pathway of complement, but the spectrum and mode of interaction with pathogens are largely unknown. In this study, we investigated the binding properties of the murine serum ficolin-A towards a panel of different clinical relevant microorganisms (N = 45) and compared the binding profile with human serum ficolin-2 and ficolin-3. Ficolin-A was able to bind Gram-positive bacteria strains including E.

Allelic lineages of the ficolin genes (FCNs) are passed from ancestral to descendant primates.

The ficolins recognize carbohydrates and acetylated compounds on microorganisms and dying host cells and are able to activate the lectin pathway of the complement system. In humans, three ficolin genes have been identified: FCN1, FCN2 and FCN3, which encode ficolin-1, ficolin-2 and ficolin-3, respectively. Rodents have only two ficolins designated ficolin-A and ficolin-B that are closely related to human ficolin-1, while the rodent FCN3 orthologue is a pseudogene.

Functional analysis of Ficolin-3 mediated complement activation.

The recognition molecules of the lectin complement pathway are mannose-binding lectin and Ficolin -1, -2 and -3. Recently deficiency of Ficolin-3 was found to be associated with life threatening infections. Thus, we aimed to develop a functional method based on the ELISA platform for evaluating Ficolin-3 mediated complement activation that could be applicable for research and clinical use.

Serum concentration and interaction properties of MBL/ficolin associated protein-1.

Recently, a novel protein named MBL/ficolin associated protein-1 (MAP-1) derived from the MASP1 gene through differential splicing was identified. In the present study, we established biochemical characteristics, determined the serum level and assessed the interactions between the lectin complement pathway (LCP) recognition molecules and MAP-1. We expressed recombinant MAP-1 in CHO DG44 cells, developed a quantitative ELISA assay based on a MAP-1 specific monoclonal capture antibody and measured the serum levels in 100 Danish blood donors.

Tethering of Ficolin-1 to cell surfaces through recognition of sialic acid by the fibrinogen-like domain.

Three Ficolins have been identified in humans: Ficolin-1 (M-Ficolin), Ficolin-2 (L-Ficolin), and Ficolin-3 (H-Ficolin). Ficolin-1 is the least-described of the Ficolins and is expressed by monocytes, granulocytes, and in the lungs. Ficolin-1 is found circulating at low concentrations in serum but is regarded primarily as a secretory molecule that exerts its function locally in inflamed tissues.

The genetics of ficolins.

Ficolins constitute a family of proteins whose biological role has been an enigma for many years. Over the past few years it has become evident that ficolins are part of the innate immune system and function as recognition molecules in the complement system. The 3 human ficolins, ficolin-1 (M-ficolin), ficolin-2 (L-ficolin) and ficolin-3 (H-ficolin or Hakata antigen) are encoded by the FCN1, FCN2 and FCN3 genes, respectively.

A novel mannose-binding lectin/ficolin-associated protein is highly expressed in heart and skeletal muscle tissues and inhibits complement activation.

The human lectin complement pathway involves circulating complexes consisting of mannose-binding lectin (MBL) or three ficolins (ficolin-1, -2, and -3) in association with three MBL/ficolin-associated serine proteases (MASP) (MASP-1, -2, and -3) and a nonenzymatic sMAP. MASP-1 and MASP-3 (MASP1 isoforms 1 and 2, respectively) are splice variants of the MASP1 gene, whereas MASP-2 and sMAP are splice variants of the MASP2 gene. We have identified a novel serum protein of 45 kDa that is associated with MBL and the ficolins.

Synergy between ficolin-2 and pentraxin 3 boosts innate immune recognition and complement deposition.

The long pentraxin 3 (PTX3) is a multifunctional soluble pattern recognition molecule that is crucial in innate immune protection against opportunistic fungal pathogens such as Aspergillus fumigatus. The mechanisms that mediate downstream effects of PTX3 are largely unknown. However, PTX3 interacts with C1q from the classical pathway of the complement.

Immunodeficiency associated with FCN3 mutation and ficolin-3 deficiency.

Ficolin-3, encoded by the FCN3 gene and expressed in the lung and liver, is a recognition molecule in the lectin pathway of the complement system. Heterozygosity for an FCN3 frameshift mutation (rs28357092), leading to a distortion of the C-terminal end of the molecule, occurs in people without disease (allele frequency among whites, 0.01).

MBL2, FCN1, FCN2 and FCN3-The genes behind the initiation of the lectin pathway of complement.

Mannose-binding lectin (MBL) and the ficolins (Ficolin-1, Ficolin-2 and Ficolin-3) are soluble collagen-like proteins that are involved in innate immune defence. They bind sugar structures or acetylated compounds present on microorganisms and on dying host cells and they initiate activation of the lectin complement pathway in varying degrees. Common variant alleles situated both in promoter and structural regions of the human MBL gene (MBL2) influence the stability and the serum concentration of the protein.

Ficolins and Mannose-Binding Lectin in Danish patients with sarcoidosis.

Mannose-Binding Lectin (MBL) is a prognostic marker in pulmonary diseases. Ficolins, sharing many structural and functional similarities with MBL, may also be involved in the pathogenesis of pulmonary diseases. The objectives of the study were to establish whether plasma concentrations of Ficolin-2, -3, and MBL in Danish patients with sarcoidosis and control persons differed and whether they were of prognostic significance.

The innate pattern recognition molecule Ficolin-1 is secreted by monocytes/macrophages and is circulating in human plasma.

Ficolin-1 (M-Ficolin) is a pattern recognition molecule of the complement system that is expressed by myeloid cells and type II alveolar epithelial cells. Ficolin-1 has been shown to localize in the secretory granules of these cells and attached to cell surfaces, but whether Ficolin-1 exists a soluble molecule in the extracellular environment or in plasma is unknown. In this study we explored the possibility that Ficolin-1 may be secreted from monocytes, macrophages or immature dendritic cells and may exist in human plasma.

Functional SNPs in the human ficolin (FCN) genes reveal distinct geographical patterns.

The ficolin protein family comprises three different molecules encoded by the FCN1, FCN2, and FCN3 genes, respectively, that play roles in innate immunity. The FCN genes in Caucasians are polymorphic and genetic variations may have functional consequences both in relation to function and concentration. The ethnic diversity of the FCN genes is unknown.

Characterization of a polymorphism in the coding sequence of FCN3 resulting in a Ficolin-3 (Hakata antigen) deficiency state.

Ficolin-3 (Hakata antigen or H-ficolin) is a soluble pattern recognition molecule in the lectin complement pathway. We speculated whether common genetic variations in the FCN3 gene contribute to deficiency of Ficolin-3. The FCN3 gene was sequenced in 237 healthy Danish Caucasians.

Comparative study of the human ficolins reveals unique features of Ficolin-3 (Hakata antigen).

The ficolins and mannose-binding lectin (MBL) are collagen-like defence proteins that serve as recognition molecules in lectin complement pathway. Differential features that may indicate diverse functions of these proteins are poorly understood. In this study we compared important biological features of the ficolins and MBL.

The innate immune component ficolin 3 (Hakata antigen) mediates the clearance of late apoptotic cells.

Objective: Ficolin 3 (Hakata antigen), a collagen-like defense molecule, is a known autoantigen in patients with systemic lupus erythematosus (SLE). Recent studies have shown that other collagen-like defense molecules, such as C1q, mannose-binding lectin (MBL) and ficolin 2, bind to apoptotic cells and mediate their clearance by phagocytic cells. Dysfunction in this mechanism is regarded as an important contributor to the pathophysiology of SLE.

Ficolin-2 recognizes DNA and participates in the clearance of dying host cells.

Ficolin-2 is a serum opsonin, which has been shown to be a pattern recognition molecule in the lectin complement activation pathway. Because innate immune mechanisms are involved in maintaining tissue homeostasis we hypothesized that Ficolin-2 also participate in the clearance of dying host cells. We found that Ficolin-2 binds to late apoptotic cells, as well as to apoptotic bodies and necrotic cells, but not to early apoptotic cells.

Molecular organization of human Ficolin-2.

Human Ficolin-2 (L-Ficolin) is an oligomeric serum protein consisting of a collagen-like stalk and fibrinogen-like recognition domains. The protein binds to arrays of sugars present on different microorganisms, enhances phagocytosis and promotes activation of the lectin complement pathway. So far the detailed oligomeric structure and composition of human Ficolin-2 has not been determined.

A functional polymorphism in the Eta-1 promoter is associated with allele specific binding to the transcription factor Sp1 and elevated gene expression.

Early T lymphocyte activator 1 (Eta-1), also known as Osteopontin, is a cytokine produced by macrophages and T lymphocytes. It is involved in the regulation of IL-12 and IL-10 expression in macrophages and stimulates the polarization of T cells to the Th1 subset. Three promoter polymorphisms of the human Eta-1 gene, -443T/C, -156delG/G, -66T/G, were investigated for possible influence on gene expression.

Polymorphisms in the FCN2 gene determine serum variation and function of Ficolin-2.

The ficolin 1, 2 and 3 (derived from the FCN1, 2 and 3 genes, respectively) are homologous soluble pattern recognition molecules of importance for innate immunity, comprising collagen-like and fibrinogen-like domains, binding to sugar groups on different types of microorganisms. Serum concentration of Ficolin-2 varies considerably in healthy individuals. Thus, we speculated whether this could be due to variations in the FCN2 gene.