Anti-serpin antibody-mediated regulation of proteases in autoimmune diabetes

Autoantibodies against PIP4K2B and AKT3 Are Associated with Skin and Lung Fibrosis in Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is a rare autoimmune systemic disease that leads to decreased survival and quality of life due to fibrosis, inflammation, and vascular damage in the skin and/or vital organs. Early diagnosis is crucial for clinical benefit in SSc patients. Our study aimed to identify autoantibodies in the plasma of SSc patients that are associated with fibrosis in SSc. Initially, we performed a proteome-wide screening on sample pools from SSc patients by untargeted autoantibody screening on a planar antigen array (including 42,000 antigens representing 18,000 unique proteins). The selection was complemented with proteins reported in the literature in the context of SSc. A targeted antigen bead array was then generated with protein fragments representing the selected proteins and used to screen 55 SSc plasma samples and 52 matched controls. We found eleven autoantibodies with a higher prevalence in SSc patients than in controls, eight of which bound to proteins associated with fibrosis. Combining these autoantibodies in a panel could lead to the subgrouping of SSc patients with fibrosis. Anti-Phosphatidylinositol-5-phosphate 4-kinase type 2 beta (PIP4K2B)- and anti-AKT Serine/Threonine Kinase 3 (AKT3)-antibodies should be further explored to confirm their association with skin and lung fibrosis in SSc patients.

The Role of Proteases and Serpin Protease Inhibitors in β-Cell Biology and Diabetes

Regulation of the equilibrium between proteases and their inhibitors is fundamental to health maintenance. Consequently, developing a means of targeting protease activity to promote tissue regeneration and inhibit inflammation may offer a new strategy in therapy development for diabetes and other diseases. Specifically, recent efforts have focused on serine protease inhibitors, known as serpins, as potential therapeutic targets. The serpin protein family comprises a broad range of protease inhibitors, which are categorized into 16 clades that are all extracellular, with the exception of Clade B, which controls mostly intracellular proteases, including both serine- and papain-like cysteine proteases. This review discusses the most salient, and sometimes opposing, views that either inhibition or augmentation of protease activity can bring about positive outcomes in pancreatic islet biology and inflammation. These potential discrepancies can be reconciled at the molecular level as specific proteases and serpins regulate distinct signaling pathways, thereby playing equally distinct roles in health and disease development.

SerpinB13 antibodies promote β cell development and resistance to type 1 diabetes

Pancreatic endocrine cell development is dependent on the rescue of the neurogenin3 (Ngn3) transcription factor from repression by Notch. The signals that prevent Notch signaling, thereby allowing the formation of pancreatic endocrine cells, remain unclear. We show that inhibiting serpinB13, a cathepsin L (CatL) protease inhibitor expressed in the pancreatic epithelium, caused in vitro and in vivo cleavage of the extracellular domain of Notch1. This was followed by a twofold increase in the Ngn3⁺ progenitor cell population and enhanced conversion of these cells to express insulin. Conversely, both recombinant serpinB13 protein and CatL deficiency down-regulated pancreatic Ngn3⁺ cell output. Mouse embryonic exposure to inhibitory anti-serpinB13 antibody resulted in increased islet cell mass and improved outcomes in streptozotocin-induced diabetes at 8 weeks of age. Moreover, anti-serpinB13 autoantibodies stimulated Ngn3⁺ endocrine progenitor formation in the pancreas and were associated with delayed progression to type 1 diabetes (T1D) in children. These data demonstrate long-term impact of serpinB13 activity on islet biology and suggest that promoting protease activity by blocking this serpin may have prophylactic potential in T1D.

Eupatilin Promotes Cell Death by Calcium Influx through ER-Mitochondria Axis with SERPINB11 Inhibition in Epithelial Ovarian Cancer

Ovarian cancer is the leading cause of gynecological cancer-related mortality. The anticancer effect of eupatilin, a family of flavonoids, is known in many cancer types, but it is unclear what mechanism it plays in ovarian cancer. In this study, eupatilin promoted cell death of ovarian cancer cells by activating caspases, cell cycle arrest, reactive oxygen species (ROS) generation, calcium influx, disruption of the endoplasmic reticulum (ER)–mitochondria axis with SERPINB11 inhibition, and downregulation of phosphoinositide 3-kinase (PI3K) and mitogen activated protein kinase (MAPK) pathways. Additionally, eupatilin-reduced SERPINB11 expression enhanced the effect of conventional chemotherapeutic agents against ovarian cancer cell progression. Cotreatment with siSERPINB11 and eupatilin increased calcium-ion-dependent apoptotic activity in ovarian cancer cells. Although there were no significant toxic effects of eupatilin on embryos, eupatilin completely inhibited tumorigenesis in a zebrafish xenograft model. In addition, eupatilin suppressed angiogenesis in zebrafish transgenic models. Collectively, downregulating SERPINB11 with eupatilin against cancer progression may improve therapeutic activity.

Cellular proliferation in mouse and human pancreatic islets is regulated by serpin B13 inhibition and downstream targeting of E-cadherin by cathepsin L

AIMS/HYPOTHESIS

We previously reported that exposure to antibodies neutralising serpin B13, a protease inhibitor expressed in exocrine pancreatic ducts, promotes beta cell proliferation, underscoring the importance of a functional relationship between exocrine and endocrine pancreas. The aim of the present study was to identify the molecular events that link inhibition of serpin B13 to islet cell proliferation.

METHODS

We used an in vitro culture system consisting of isolated pancreatic islets, an extract of pancreatic ductal epithelium and a monoclonal antibody (mAb) to serpin B13 or IgG isotype control. In vivo studies involved treatment of mice with these mAbs.

RESULTS

The catalytic activity of cathepsin L (CatL), a cysteine protease target of serpin B13, was augmented in the pancreas of mice injected with serpin B13 mAb. Furthermore, the addition of serpin B13 mAb to the islets, together with the pancreatic ductal epithelium lysate, caused CatL-dependent cleavage of E-cadherin and concomitant upregulation of REG genes, ultimately leading to beta cell proliferation. Direct blockade of E-cadherin with mAb also markedly enhanced REG gene induction, while chemical inhibition of β-catenin, a binding target of E-cadherin, prevented the serpin B13 mAb-induced upregulation of REG genes.

CONCLUSIONS/INTERPRETATION

Our work implicates the CatL-E-cadherin-REG pathway in the regulation of islet cell proliferation in response to signals generated in exocrine pancreatic tissue and demonstrates that protease activity may promote adaptive changes in the islets.

DATA AVAILABILITY

Microarray data that support the findings of this study have been deposited in Gene Expression Omnibus (GEO) with the accession no. GSE125151.

Functional characterization of the clade B serine protease inhibitor SerpinB3 in the pacific white shrimp Litopenaeus vannamei

The clade B serpins contain predominantly intracellular proteins and were reported to be involved in multiple biological functions, especially in inflammation and immune system function. However, studies about the role of the invertebrate intracellular serpins in immune responses were still deficient. Therefore, this paper focused on the functional characterization of LvserpinB3 in white shrimp Litopenaeus vannamei. The pAc5.1-LvserpinB3-EGFP vector was transfected into Drosophila Schneider 2 (S2) cells to analyze the subcellular localization of LvserpinB3, and fluorescent imaging showed that LvserpinB3 were mainly localized to the mitochondria. Knockdown LvserpinB3 significantly increased the mRNA expression of LvSpätzle4 (LvSpz4) and LvPenaeidin4 (LvPen4) upon Vibrio anguillarum infection. Moreover, GST-Pull down analysis showed that LvserpinB3 could interact with serine protease 1 (LvSP1). The recombinant LvserpinB3 (rLvserpinB3) protein exhibited inhibitory roles on the proteolytic activity of trypsin, whereas, mutation at the P1 residue led to the disfunction of the inhibitor. Furthermore, the LvserpinB3 and trypsin mixture were incubated with Anti-SERPINB3 antibodies, and a peptide band with an apparent molecular weight of 30 kDa were detected by western blot analysis. These findings might be valuable in understanding the potential role for LvserpinB3 in inhibiting the target proteases during shrimp immune defences.

Antibody Response to Serpin B13 Induces Adaptive Changes in Mouse Pancreatic Islets and Slows Down the Decline in the Residual Beta Cell Function in Children with Recent Onset of Type 1 Diabetes Mellitus

Type 1 diabetes mellitus (T1D) is characterized by a heightened antibody (Ab) response to pancreatic islet self-antigens, which is a biomarker of progressive islet pathology. We recently identified a novel antibody to clade B serpin that reduces islet-associated T cell accumulation and is linked to the delayed onset of T1D. As natural immunity to clade B arises early in life, we hypothesized that it may influence islet development during that time. To test this possibility healthy young Balb/c male mice were injected with serpin B13 mAb or IgG control and examined for the number and cellularity of pancreatic islets by immunofluorescence and FACS. Beta cell proliferation was assessed by measuring nucleotide analog 5-ethynyl-2'-deoxyuridine (5-EdU) incorporation into the DNA and islet Reg gene expression was measured by real time PCR. Human studies involved measuring anti-serpin B13 autoantibodies by Luminex. We found that injecting anti-serpin B13 monoclonal Ab enhanced beta cell proliferation and Reg gene expression, induced the generation of ∼80 pancreatic islets per animal, and ultimately led to increase in the beta cell mass. These findings are relevant to human T1D because our analysis of subjects just diagnosed with T1D revealed an association between baseline anti-serpin activity and slower residual beta cell function decline in the first year after the onset of diabetes. Our findings reveal a new role for the anti-serpin immunological response in promoting adaptive changes in the endocrine pancreas and suggests that enhancement of this response could potentially help impede the progression of T1D in humans.

Update of the human and mouse SERPIN gene superfamily

The serpin family comprises a structurally similar, yet functionally diverse, set of proteins. Named originally for their function as serine proteinase inhibitors, many of its members are not inhibitors but rather chaperones, involved in storage, transport, and other roles. Serpins are found in genomes of all kingdoms, with 36 human protein-coding genes and five pseudogenes. The mouse has 60 Serpin functional genes, many of which are orthologous to human SERPIN genes and some of which have expanded into multiple paralogous genes. Serpins are found in tissues throughout the body; whereas most are extracellular, there is a class of intracellular serpins. Serpins appear to have roles in inflammation, immune function, tumorigenesis, blood clotting, dementia, and cancer metastasis. Further characterization of these proteins will likely reveal potential biomarkers and therapeutic targets for disease.

Simulating an infection growth model in certain healthy metabolic pathways of Homo sapiens for highlighting their role in Type I Diabetes mellitus using fire-spread strategy, feedbacks and sensitivities

Disease Systems Biology is an area of life sciences, which is not very well understood to date. Analyzing infections and their spread in healthy metabolite networks can be one of the focussed areas in this regard. We have proposed a theory based on the classical forest fire model for analyzing the path of infection spread in healthy metabolic pathways. The theory suggests that when fire erupts in a forest, it spreads, and the surrounding trees also catch fire. Similarly, when we consider a metabolic network, the infection caused in the metabolites of the network spreads like a fire. We have constructed a simulation model which is used to study the infection caused in the metabolic networks from the start of infection, to spread and ultimately combating it. For implementation, we have used two approaches, first, based on quantitative strategies using ordinary differential equations and second, using graph-theory based properties. Furthermore, we are using certain probabilistic scores to complete this task and for interpreting the harm caused in the network, given by a 'critical value' to check whether the infection can be cured or not. We have tested our simulation model on metabolic pathways involved in Type I Diabetes mellitus in Homo sapiens. For validating our results biologically, we have used sensitivity analysis, both local and global, as well as for identifying the role of feedbacks in spreading infection in metabolic pathways. Moreover, information in literature has also been used to validate the results. The metabolic network datasets have been collected from the Kyoto Encyclopedia of Genes and Genomes (KEGG).