Modulation of the proteolytic activity of the complement protease C1s by polyanions: implications for polyanion-mediated acceleration of interaction between C1s and SERPING1

Identification of the common differentially expressed genes and pathogenesis between neuropathic pain and aging

Background

Neuropathic pain is a debilitating disease caused by damage or diseases of the somatosensory nervous system. Previous research has indicated potential associations between neuropathic pain and aging. However, the mechanisms by which they are interconnected remain unclear. In this study, we aim to identify the common differentially expressed genes (co-DEGs) between neuropathic pain and aging through integrated bioinformatics methods and further explore the underlying molecular mechanisms.

Methods

The microarray datasets GSE24982, GSE63442, and GSE63651 were downloaded from Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) and co-DEGs were first identified. Functional enrichment analyses, protein-protein Interaction (PPI) network, module construction and hub genes identification were performed. Immune infiltration analysis was conducted. Targeted transcription factors (TFs), microRNAs (miRNAs) and potential effective drug compounds for hub genes were also predicted.

Results

A total of 563 and 1,250 DEGs of neuropathic pain and aging were screened, respectively. 16 genes were further identified as co-DEGs. The functional analysis emphasizes the vital roles of the humoral immune response and complement and coagulation cascades in these two diseases. Cxcl14, Fblim1, RT1-Da, Serping1, Cfd, and Fcgr2b were identified as hub genes. Activated B cell, mast cell, activated dendritic cell, CD56 bright natural killer cell, effector memory CD8 + T cell, and type 2 T helper cell were significantly up-regulated in the pain and aging condition. Importantly, hub genes were found to correlate with the activated B cell, activated dendritic cell, Gamma delta T cell, central memory CD4 + T cell and mast cell in pain and aging diseases. Finally, Spic, miR-883-5p, and miR-363-5p et al. were predicted as the potential vital regulators for hub genes. Aldesleukin, Valziflocept, MGD-010, Cinryze, and Rhucin were the potential effective drugs in neuropathic pain and aging.

Conclusion

This study identified co-DEGs, revealed molecular mechanisms, demonstrated the immune microenvironment, and predicted the possible TFs, miRNAs regulation networks and new drug targets for neuropathic pain and aging, providing novel insights into further research.

Mapping the binding site of C1-inhibitor for polyanion cofactors

The serpin, C1-inhibitor (also known as SERPING1), plays a vital anti-inflammatory role in the body by controlling pro-inflammatory pathways such as complement and coagulation. The inhibitor's action is enhanced in the presence of polyanionic cofactors, such as heparin and polyphosphate, by increasing the rate of association with key enzymes such as C1s of the classical pathway of complement. The cofactor binding site of the serpin has never been mapped. Here we show that residues Lys284, Lys285 and Arg287 of C1-inhibitor play key roles in binding heparin and delivering the rate enhancement seen in the presence of polyanions and thus most likely represent the key cofactor binding residues for the serpin. We also show that simultaneous binding of the anion binding site of C1s by the polyanion is required to deliver the rate enhancement. Finally, we have shown that it is unlikely that the two positively charged zones of C1-inhibitor and C1s interact in the encounter complex between molecules as ablation of the charged zones did not in itself deliver a rate enhancement as might have been expected if the zones interacted. These insights provide crucial information as to the mechanism of action of this key serpin in the presence and absence of cofactor molecules.

NF-κB p50 activation associated with immune dysregulation confers poorer survival for diffuse large B-cell lymphoma patients with wild-type p53

Dysregulated NF-κB signaling is critical for lymphomagenesis, however, the expression and clinical relevance of NF-κB subunit p50 in diffuse large B-cell lymphoma have not been evaluated. In this study, we analyzed the prognostic significance and gene expression signatures of p50 nuclear expression as a surrogate for p50 activation in 465 patients with de novo diffuse large B-cell lymphoma. We found that p50⁺ nuclear expression, observed in 34.6% of diffuse large B-cell lymphoma, predominantly composed of activated B-cell-like subtype, was an independent adverse prognostic factor in patients with activated B-cell-like diffuse large B-cell lymphoma. It was also an adverse prognostic factor in patients with wild-type TP53 independent of the activated B-cell-like and germinal center B-cell-like subtypes, even though p50 activation correlated with significantly lower levels of Myc, PI3K, phospho-AKT, and CXCR4 expression and less frequent BCL2 translocations. In contrast, in germinal center B-cell-like diffuse large B-cell lymphoma patients with TP53 mutations, p50⁺ nuclear expression correlated with significantly better clinical outcomes, and decreased p53, Bcl-2, and Myc expression. Gene expression profiling revealed multiple signaling pathways potentially upstream the p50 activation through either canonical or noncanonical NF-κB pathways, and suggested that immune suppression, including that by the immune checkpoint TIM-3 and that through leukocyte immunoglobulin-like receptors, but not antiapoptosis and proliferation, may underlie the observed poorer survival rates associated with p50⁺ nuclear expression in diffuse large B-cell lymphoma. In conclusion, these data show that p50 is important as a unique mechanism of R-CHOP-resistance in activated B-cell-like diffuse large B-cell lymphoma and in patients without TP53 mutations. The results also provide insights into the regulation and function of p50 in diffuse large B-cell lymphoma and its cross talk with the p53 pathway with important therapeutic implications.

Regulation of Complement and Contact System Activation via C1 Inhibitor Potentiation and Factor XIIa Activity Modulation by Sulfated Glycans - Structure-Activity Relationships

The serpin C1 inhibitor (C1-INH) is the only regulator of classical complement activation as well as the major regulator of the contact system. Its importance is demonstrated by hereditary angioedema (HAE), a severe disease with potentially life-threatening attacks due to deficiency or dysfunction of C1-INH. C1-INH replacement is the therapy of choice in HAE. In addition, C1-INH showed to have beneficial effects in other diseases characterized by inappropriate complement and contact system activation. Due to some limitations of its clinical application, there is a need for improving the efficacy of therapeutically applied C1-INH or to enhance the activity of endogenous C1-INH. Given the known potentiating effect of heparin on C1-INH, sulfated glycans (SG) may be such candidates. The aim of this study was to characterize suitable SG by evaluating structure-activity relationships. For this, more than 40 structurally distinct SG were examined for their effects on C1-INH, C1s and FXIIa. The SG turned out to potentiate the C1s inhibition by C1-INH without any direct influence on C1s. Their potentiating activity proved to depend on their degree of sulfation, molecular mass as well as glycan structure. In contrast, the SG had no effect on the FXIIa inhibition by C1-INH, but structure-dependently modulated the activity of FXIIa. Among the tested SG, β-1,3-glucan sulfates with a Mr ≤ 10 000 were identified as most promising lead candidates for the development of a glycan-based C1-INH amplifier. In conclusion, the obtained information on structural characteristics of SG favoring C1-INH potentiation represent an useful elementary basis for the development of compounds improving the potency of C1-INH in diseases and clinical situations characterized by inappropriate activation of complement and contact system.

Polyphosphate is a novel cofactor for regulation of complement by a serpin, C1 inhibitor

The complement system plays a key role in innate immunity, inflammation, and coagulation. The system is delicately balanced by negative regulatory mechanisms that modulate the host response to pathogen invasion and injury. The serpin, C1-esterase inhibitor (C1-INH), is the only known plasma inhibitor of C1s, the initiating serine protease of the classical pathway of complement. Like other serpin-protease partners, C1-INH interaction with C1s is accelerated by polyanions such as heparin. Polyphosphate (polyP) is a naturally occurring polyanion with effects on coagulation and complement. We recently found that polyP binds to C1-INH, prompting us to consider whether polyP acts as a cofactor for C1-INH interactions with its target proteases. We show that polyP dampens C1s-mediated activation of the classical pathway in a polymer length- and concentration-dependent manner by accelerating C1-INH neutralization of C1s cleavage of C4 and C2. PolyP significantly increases the rate of interaction between C1s and C1-INH, to an extent comparable to heparin, with an exosite on the serine protease domain of the enzyme playing a major role in this interaction. In a serum-based cell culture system, polyP significantly suppressed C4d deposition on endothelial cells, generated via the classical and lectin pathways. Moreover, polyP and C1-INH colocalize in activated platelets, suggesting that their interactions are physiologically relevant. In summary, like heparin, polyP is a naturally occurring cofactor for the C1s:C1-INH interaction and thus an important regulator of complement activation. The findings may provide novel insights into mechanisms underlying inflammatory diseases and the development of new therapies.

Identification of a catalytic exosite for complement component C4 on the serine protease domain of C1s

The classical pathway of complement is crucial to the immune system, but it also contributes to inflammatory diseases when dysregulated. Binding of the C1 complex to ligands activates the pathway by inducing autoactivation of associated C1r, after which C1r activates C1s. C1s cleaves complement component C4 and then C2 to cause full activation of the system. The interaction between C1s and C4 involves active site and exosite-mediated events, but the molecular details are unknown. In this study, we identified four positively charged amino acids on the serine protease domain that appear to form a catalytic exosite that is required for efficient cleavage of C4. These residues are coincidentally involved in coordinating a sulfate ion in the crystal structure of the protease. Together with other evidence, this pointed to the involvement of sulfate ions in the interaction with the C4 substrate, and we showed that the protease interacts with a peptide from C4 containing three sulfotyrosine residues. We present a molecular model for the interaction between C1s and C4 that provides support for the above data and poses questions for future research into this aspect of complement activation.

Immunoprotective properties of primary Sertoli cells in mice: potential functional pathways that confer immune privilege

Primary Sertoli cells isolated from mouse testes survive when transplanted across immunological barriers and protect cotransplanted allogeneic and xenogeneic cells from rejection in rodent models. In contrast, the mouse Sertoli cell line (MSC-1) lacks immunoprotective properties associated with primary Sertoli cells. In this study, enriched primary Sertoli cells or MSC-1 cells were transplanted as allografts into the renal subcapsular area of naive BALB/c mice, and their survival in graft sites was compared. While Sertoli cells were detected within the grafts with 100% graft survival throughout the 20-day study, MSC-1 cells were rejected between 11 and 14 days, with 0% graft survival at 20 days posttransplantation. Nonetheless, the mechanism for primary Sertoli cell survival and immunoprotection remains unresolved. To identify immune factors or functional pathways potentially responsible for immune privilege, gene expression profiles of enriched primary Sertoli cells were compared with those of MSC-1 cells. Microarray analysis identified 2369 genes in enriched primary Sertoli cells that were differentially expressed at ±4-fold or higher levels than in MSC-1 cells. Ontological analyses identified multiple immune pathways, which were used to generate a list of 340 immune-related genes. Three functions were identified in primary Sertoli cells as potentially important for establishing immune privilege: suppression of inflammation by specific cytokines and prostanoid molecules, slowing of leukocyte migration by controlled cell junctions and actin polymerization, and inhibition of complement activation and membrane-associated cell lysis. These results increase our understanding of testicular immune privilege and, in the long-term, could lead to improvements in transplantation success.

Potentiation of C1-esterase inhibitor by heparin and interactions with C1s protease as assessed by surface plasmon resonance

BACKGROUND

Human C1-esterase inhibitor (C1-INH) is a multifunctional plasma protein with a wide range of inhibitory and non-inhibitory properties, mainly recognized as a key down-regulator of the complement and contact cascades. The potentiation of C1-INH by heparin and other glycosaminoglycans (GAGs) regulates a broad spectrum of C1-INH activities in vivo both in normal and disease states. SCOPE OF RESEARCH: We have studied the potentiation of human C1-INH by heparin using Surface Plasmon Resonance (SPR), circular dichroism (CD) and a functional assay. To advance a SPR for multiple-unit interaction studies of C1-INH we have developed a novel (consecutive double capture) approach exploring different immobilization and layout.

MAJOR CONCLUSIONS

Our SPR experiments conducted in three different design versions showed marked acceleration in C1-INH interactions with complement protease C1s as a result of potentiation of C1-INH by heparin (from 5- to 11-fold increase of the association rate). Far-UV CD studies suggested that heparin binding did not alter C1-INH secondary structure. Functional assay using chromogenic substrate confirmed that heparin does not affect the amidolytic activity of C1s, but does accelerate its consumption due to C1-INH potentiation.

GENERAL SIGNIFICANCE

This is the first report that directly demonstrates a significant acceleration of the C1-INH interactions with C1s due to heparin by using a consecutive double capture SPR approach. The results of this study may be useful for further C-INH therapeutic development, ultimately for the enhancement of current C1-INH replacement therapies.