Glycosylation of a disintegrin and metalloprotease 17 affects its activity and inhibition

The Biochemistry and Physiology of A Disintegrin and Metalloproteinases (ADAMs and ADAM-TSs) in Human Pathologies

Metalloproteinases are a group of proteinases that plays a substantial role in extracellular matrix remodeling and its molecular signaling. Among these metalloproteinases, ADAMs (a disintegrin and metalloproteinases) and ADAM-TSs (ADAMs with thrombospondin domains) have emerged as highly efficient contributors mediating proteolytic processing of various signaling molecules. ADAMs are transmembrane metalloenzymes that facilitate the extracellular domain shedding of membrane-anchored proteins, cytokines, growth factors, ligands, and their receptors and therefore modulate their biological functions. ADAM-TSs are secretory, and soluble extracellular proteinases that mediate the cleavage of non-fibrillar extracellular matrix proteins. ADAMs and ADAM-TSs possess pro-domain, metalloproteinase, disintegrin, and cysteine-rich domains in common, but ADAM-TSs have characteristic thrombospondin motifs instead of the transmembrane domain. Most ADAMs and ADAM-TSs are activated by cleavage of pro-domain via pro-protein convertases at their N-terminus, hence directing them to various signaling pathways. In this article, we are discussing not only the structure and regulation of ADAMs and ADAM-TSs, but also the importance of these metalloproteinases in various human pathophysiological conditions like cardiovascular diseases, colorectal cancer, autoinflammatory diseases (sepsis/rheumatoid arthritis), Alzheimer's disease, proliferative retinopathies, and infectious diseases. Therefore, based on the emerging role of ADAMs and ADAM-TSs in various human pathologies, as summarized in this review, these metalloproteases can be considered as critical therapeutic targets and diagnostic biomarkers.

Immunomodulatory role of metalloproteinase ADAM17 in tumor development

ADAM17 is a member of the a disintegrin and metalloproteinase (ADAM) family of transmembrane proteases involved in the shedding of some cell membrane proteins and regulating various signaling pathways. More than 90 substrates are regulated by ADAM17, some of which are closely relevant to tumor formation and development. Besides, ADAM17 is also responsible for immune regulation and its substrate-mediated signal transduction. Recently, ADAM17 has been considered as a major target for the treatment of tumors and yet its immunomodulatory roles and mechanisms remain unclear. In this paper, we summarized the recent understanding of structure and several regulatory roles of ADAM17. Importantly, we highlighted the immunomodulatory roles of ADAM17 in tumor development, as well as small molecule inhibitors and monoclonal antibodies targeting ADAM17.

N-glycosylation modulates enzymatic activity of Trypanosoma congolense trans-sialidase

Trypanosomes cause the devastating disease trypanosomiasis, in which the action of trans-sialidase (TS) enzymes harbored on their surface is a key virulence factor. TS enzymes are N-glycosylated, but the biological functions of their glycans have remained elusive. In this study, we investigated the influence of N-glycans on the enzymatic activity and structural stability of TconTS1, a recombinant TS from the African parasite Trypanosoma congolense. We expressed the enzyme in Chinese hamster ovary Lec1 cells, which produce high-mannose type N-glycans similar to the TS N-glycosylation pattern in vivo. Our MALDI-TOF mass spectrometry data revealed that up to eight putative N-glycosylation sites were glycosylated. In addition, we determined that N-glycan removal via endoglycosidase H_f treatment of TconTS1 led to a decrease in substrate affinity relative to the untreated enzyme but had no impact on the conversion rate. Furthermore, we observed no changes in secondary structure elements of hypoglycosylated TconTS1 in CD experiments. Finally, our molecular dynamics simulations provided evidence for interactions between monosaccharide units of the highly flexible N-glycans and some conserved amino acids located at the catalytic site. These interactions led to conformational changes, possibly enhancing substrate accessibility and enzyme–substrate complex stability. The here-observed modulation of catalytic activity via N-glycans represents a so-far-unknown structure–function relationship potentially inherent in several members of the TS enzyme family.

Molecular switch in human diseases-disintegrin and metalloproteinases, ADAM17

The ADAMs (a disintegrin and metalloproteinase) are a family of cell surface proteins with crucial roles in the regulation of cell adhesion, cell proliferation to migration, proteolysis and cell signaling transduction pathways. Among these enzymes, the ADAM17 shows significant effects in the “ectodomain shedding” of its substrates such as cytokines (e.g., tumor necrosis factor α, TNFα), growth factors (e.g., epidermal growth factor, EGF), adhesion proteins (e.g., L-selectin), and their receptors (e.g., IL-6R and TNFα). Several studies focus on the underlying molecular mechanisms of ADAM17 in diseased conditions. Here, we took several different approaches to elucidate the function of ADAM17, the participation of ADAM17 in several human diseases, and the potential as targeted therapy reagents. As more and more studies verify the miRNA-mediated expression variation of ADAM17, the specific regulation network of miRNAs and ADAM17 was exploited in this review as well.

An antibody-based enzymatic therapy for cancer treatment: The selective localization of D-amino acid oxidase to EDA fibronectin

In order to generate an antibody directed enzyme prodrug therapy, here we designed a chimeric protein by fusing the F8 antibody that recognizes the EDA of fibronectin (expressed on the tumor neovasculature) and an evolved variant of the ROS-generating enzyme D-amino acid oxidase (DAAO). The F8(scFv)-DAAO-Q144R recombinant protein is expressed by both CHO-S and E. coli cells. The F8(scFv)-DAAO-Q144R from E. coli cells is fully soluble, shows a high specific activity, is more thermostable in blood than the native DAAO, possesses a binding affinity for EDA well suited for efficient tumor accumulation, and localizes in tumor tissues. Notably, the F8(scFv)-DAAO-Q144R conjugate generates a stronger cytotoxicity to tumor cells than the native enzyme, especially when an inhibitor of heme oxygenase-1 (HO-1) is used, making it a promising candidate for a selective antitumor oxidative therapy controlled by the substrate addition, in the so called "activity on demand", thus sparing normal tissue from damage.

Strategies to Target ADAM17 in Disease: From its Discovery to the iRhom Revolution

For decades, disintegrin and metalloproteinase 17 (ADAM17) has been the object of deep investigation. Since its discovery as the tumor necrosis factor convertase, it has been considered a major drug target, especially in the context of inflammatory diseases and cancer. Nevertheless, the development of drugs targeting ADAM17 has been harder than expected. This has generally been due to its multifunctionality, with over 80 different transmembrane proteins other than tumor necrosis factor α (TNF) being released by ADAM17, and its structural similarity to other metalloproteinases. This review provides an overview of the different roles of ADAM17 in disease and the effects of its ablation in a number of in vivo models of pathological conditions. Furthermore, here, we comprehensively encompass the approaches that have been developed to accomplish ADAM17 selective inhibition, from the newest non-zinc-binding ADAM17 synthetic inhibitors to the exploitation of iRhom2 to specifically target ADAM17 in immune cells.

Depolarization-dependent Induction of Site-specific Changes in Sialylation on N-linked Glycoproteins in Rat Nerve Terminals

Synaptic transmission leading to release of neurotransmitters in the nervous system is a fast and highly dynamic process. Previously, protein interaction and phosphorylation have been thought to be the main regulators of synaptic transmission. Here we show that sialylation of N-linked glycosylation is a novel potential modulator of neurotransmitter release mechanisms by investigating depolarization-dependent changes of formerly sialylated N-linked glycopeptides. We suggest that negatively charged sialic acids can be modulated, similarly to phosphorylation, by the action of sialyltransferases and sialidases thereby changing local structure and function of membrane glycoproteins. We characterized site-specific alteration in sialylation on N-linked glycoproteins in isolated rat nerve terminals after brief depolarization using quantitative sialiomics. We identified 1965 formerly sialylated N-linked glycosites in synaptic proteins and found that the abundances of 430 glycosites changed after 5 s depolarization. We observed changes on essential synaptic proteins such as synaptic vesicle proteins, ion channels and transporters, neurotransmitter receptors and cell adhesion molecules. This study is to our knowledge the first to describe ultra-fast site-specific modulation of the sialiome after brief stimulation of a biological system.

Novel Approaches and Challenges of Discovery of Exosite Modulators of a Disintegrin and Metalloprotease 10

A disintegrin and metaproteinase 10 is an important target for multiple therapeutic areas, however, despite drug discovery efforts by both industry and academia no compounds have reached the clinic so far. The lack of enzyme and substrate selectivity of developmental drugs is believed to be a main obstacle to the success. In this review, we will focus on novel approaches and associated challenges in discovery of ADAM10 selective modulators that can overcome shortcomings of previous generations of compounds and be translated into the clinic.

ADAM Metalloproteinases as Potential Drug Targets

The ADAMs, together with ADAMTSs and snake venom metalloproteases (SVMPs), are members of the Adamalysin family. Differences in structural organization, functions and localization are known and their domains, catalytic or non-catalytic, show key roles in the substrate recognition and protease activity. Some ADAMs, as membrane-bound enzymes, show sheddase activity. Sheddases are key to modulation of functional proteins such as the tumor necrosis factor, growth factors, cytokines and their receptors, adhesion proteins, signaling molecules and stress molecules involved in immunity. These activities take part in the regulation of several physiological and pathological processes including inflammation, tumor growth, metastatic progression and infectious diseases. On these bases, some ADAMs are currently investigated as drug targets to develop new alternative therapies in many fields of medicine. This review will be focused on these aspects.

Functional Characterization of Colon Cancer-Associated Mutations in ADAM17: Modifications in the Pro-Domain Interfere with Trafficking and Maturation

Colorectal cancer is one of the most commonly diagnosed malignancies in the Western world and is associated with elevated expression and activity of epidermal growth factor receptors (EGF-R). The metalloproteinase ADAM17 is involved in EGF-R activation by processing EGF-R ligands from membrane-bound pro-ligands. Underlining the link between colon cancer and ADAM17, genetic intestinal cancer models in ADAM17-deficient mice show a reduced tumor burden. In this study, we characterize point mutations within the ADAM17 gene found in the tissue of colon cancer patients. In order to shed light on the role of ADAM17 in cancer development, as well as into the mechanisms that regulate maturation and cellular trafficking of ADAM17, we here perform overexpression studies of four ADAM17 variants located in the pro-, membrane-proximal- and cytoplasmic-domain of the ADAM17 protein in ADAM10/17-deficient HEK cells. Interestingly, we found a cancer-associated point mutation within the pro-domain of ADAM17 (R177C) to be most impaired in its proteolytic activity and trafficking to the cell membrane. By comparing this variant to an ADAM17 construct lacking the entire pro-domain, we discovered similar functional limitations and propose a crucial role of the pro-domain for ADAM17 maturation, cellular trafficking and thus proteolytic activity.

Leucurogin and melanoma therapy

Leucurogin is an ECD disintegrin-like protein, cloned from Bothrops leucurus venom gland. This new protein, encompassing the disintegrin region of a PIII metalloproteinase, is produced by recombinant technology and its biological and functional activity was partially characterized in this study. Biological activity was characterized in vitro using human fibroblasts. Functional activity of leucurogin was analysed in vitro and in vivo with murine B16F10 Nex-2 and human melanoma BLM cells. The results show that leucurogin inhibits cellular processes dependent on collagen type I. In a competition assay with collagen, leucurogin inhibits, in a dose-dependent manner, the adhesion of fibroblast to collagen. At 10 μM leucurogin reduces adhesion (40%) and migration (70%) of hFb and inhibits migration (32%) and proliferation (65%) of BLM cells. At 2.5 μM leucurogin inhibits 80% cell proliferation of B16F10 Nex-2 melanoma cells. At 4.8 μM leucurogin inhibits, in vitro, the vascular structures formation by endothelial cells by 66%. Leucurogin, injected intraperitoneally, i.p. (5 μg/animal, two-month old C57/Bl6 male mice) on alternate days for 15 days, inhibits lung metastasis of B16F10 Nex-2 cells by 70-75%. In the treatment of human melanoma, grafted intradermally in the nude mice flank, leucurogin (7.5 μg/kg in alternate days during 17 days) inhibits tumor growth by more than 40%. Leucurogin can be considered a promising agent for melanoma treatment.

Zidovudine-Based Treatments Inhibit the Glycosylation of ADAM17 and Reduce CD163 Shedding From Monocytes

BACKGROUND

sCD163, a biomarker of monocyte-macrophage activation, has been identified as a predictor of all-cause mortality in treated HIV-infected individuals. Nevertheless, little is known about whether different antiretroviral drugs differentially regulate sCD163 levels and monocyte activation.

METHODS

A total of 123 patients receiving zidovudine (ZDV)-based (n = 55) or tenofovir disoproxil fumarate (TDF)-based (n = 68) antiretroviral regimens were enrolled, and their viral loads, CD4 counts, as well as plasma sCD163 and sCD14 levels were quantified. Twenty-eight (14 in each group) patients donated additional blood samples for flow cytometry and gene expression analyses using purified monocytes. THP-1 cultures were also used to investigate the effect of ZDV on ADAM17, which is responsible for CD163 shedding.

RESULTS

As compared to the TDF-treated group, the ZDV-treated group had lower plasma sCD163 levels and higher CD163 expression on CD14++CD16 monocytes. Five metabolic-inflammatory genes exhibited significantly different expression levels between purified monocytes of the ZDV and TDF groups (IL-6, 2.90-fold lower in ZDV group, P < 0.001; iNOS, 1.81-fold higher; CX3CR1, 1.72-fold lower; MIP-1β, 1.10-fold lower; and PPARγ-1, 1.36-fold higher, P < 0.05). Moreover, we show that ZDV treatment increases the surface expression of CD163 in cultured THP-1 cells, accompanied by the inhibition of glycosylation and surface expression of ADAM17.

CONCLUSIONS

Compared with TDF treatment, ZDV treatment causes lower plasma sCD163 levels, probably by inhibiting the glycosylation of ADAM17 and CD163 shedding. Our results show that ZDV functions as an ADAM17 inhibitor in vivo and extend our understanding of its immune-modulatory effects and adverse effects.

Functional Genomics Approach Identifies Novel Signaling Regulators of TGFα Ectodomain Shedding

Ectodomain shedding of cell-surface precursor proteins by metalloproteases generates important cellular signaling molecules. Of importance for disease is the release of ligands that activate the EGFR, such as TGFα, which is mostly carried out by ADAM17 [a member of the A-disintegrin and metalloprotease (ADAM) domain family]. EGFR ligand shedding has been linked to many diseases, in particular cancer development, growth and metastasis, as well as resistance to cancer therapeutics. Excessive EGFR ligand release can outcompete therapeutic EGFR inhibition or the inhibition of other growth factor pathways by providing bypass signaling via EGFR activation. Drugging metalloproteases directly have failed clinically because it indiscriminately affected shedding of numerous substrates. It is therefore essential to identify regulators for EGFR ligand cleavage. Here, integration of a functional shRNA genomic screen, computational network analysis, and dedicated validation tests succeeded in identifying several key signaling pathways as novel regulators of TGFα shedding in cancer cells. Most notably, a cluster of genes with NFκB pathway regulatory functions was found to strongly influence TGFα release, albeit independent of their NFκB regulatory functions. Inflammatory regulators thus also govern cancer cell growth-promoting ectodomain cleavage, lending mechanistic understanding to the well-known connection between inflammation and cancer.Implications: Using genomic screens and network analysis, this study defines targets that regulate ectodomain shedding and suggests new treatment opportunities for EGFR-driven cancers. Mol Cancer Res; 16(1); 147-61. ©2017 AACR.

Effects of Glycosylation on the Enzymatic Activity and Mechanisms of Proteases

Posttranslational modifications are an important feature of most proteases in higher organisms, such as the conversion of inactive zymogens into active proteases. To date, little information is available on the role of glycosylation and functional implications for secreted proteases. Besides a stabilizing effect and protection against proteolysis, several proteases show a significant influence of glycosylation on the catalytic activity. Glycans can alter the substrate recognition, the specificity and binding affinity, as well as the turnover rates. However, there is currently no known general pattern, since glycosylation can have both stimulating and inhibiting effects on activity. Thus, a comparative analysis of individual cases with sufficient enzyme kinetic and structural data is a first approach to describe mechanistic principles that govern the effects of glycosylation on the function of proteases. The understanding of glycan functions becomes highly significant in proteomic and glycomic studies, which demonstrated that cancer-associated proteases, such as kallikrein-related peptidase 3, exhibit strongly altered glycosylation patterns in pathological cases. Such findings can contribute to a variety of future biomedical applications.

ADAMs family and relatives in cardiovascular physiology and pathology

A disintegrin and metalloproteinases (ADAMs) are a family of membrane-bound proteases. ADAM-TSs (ADAMs with thrombospondin domains) are a close relative of ADAMs that are present in soluble form in the extracellular space. Dysregulated production or function of these enzymes has been associated with pathologies such as cancer, asthma, Alzheimer's and cardiovascular diseases. ADAMs contribute to angiogenesis, hypertrophy and apoptosis in a stimulus- and cell type-dependent manner. Among the ADAMs identified so far (34 in mouse, 21 in human), ADAMs 8, 9, 10, 12, 17 and 19 have been shown to be involved in cardiovascular development or cardiomyopathies; and among the 19 ADAM-TSs, ADAM-TS1, 5, 7 and 9 are important in development of the cardiovascular system, while ADAM-TS13 can contribute to vascular disorders. Meanwhile, there remain a number of ADAMs and ADAM-TSs whose function in the cardiovascular system has not been yet explored. The current knowledge about the role of ADAMs and ADAM-TSs in the cardiovascular pathologies is still quite limited. The most detailed studies have been performed in other cell types (e.g. cancer cells) and organs (nervous system) which can provide valuable insight into the potential functions of ADAMs and ADAM-TSs, their mechanism of action and therapeutic potentials in cardiomyopathies. Here, we review what is currently known about the structure and function of ADAMs and ADAM-TSs, and their roles in development, physiology and pathology of the cardiovascular system.

N-glycosylation regulates ADAM8 processing and activation

The transmembrane ADAM8 (A Disintegrin And Metalloproteinase 8) protein is abundantly expressed in human breast tumors and derived metastases compared with normal breast tissue, and plays critical roles in aggressive Triple-Negative breast cancers (TNBCs). During ADAM8 maturation, the inactive proform dimerizes or multimerizes and autocatalytically removes the prodomain leading to the formation of the active, processed form. ADAM8 is a glycoprotein; however, little was known about the structure or functional role of these sugar moieties. Here, we report that in estrogen receptor (ER)α-negative, but not -positive, breast cancer cells ADAM8 contains N-glycosylation, which is required for its correct processing and activation. Consistently ADAM8 dimers were detected on the surface of ERα-negative breast cancer cells but not on ERα-positive ones. Site-directed mutagenesis confirmed four N-glycosylazhytion sites (Asn-67, Asn-91, Asn-436, and Asn-612) in human ADAM8. The Asn-67 and Asn-91 prodomain sites contained high mannose, whereas complex type N-glycosylation was observed on Asn-436 and Asn-612 in the active and remnant forms. The Asn-91 and Asn-612 sites were essential for its correct processing and cell surface localization, in particular its exit from the Golgi and endoplasmic reticulum, respectively. The N436Q mutation led to decreased ADAM8 stability due to enhanced lysosomal degradation. In contrast, mutation of the Asn-67 site had only modest effects on enzyme stability and processing. Thus, N-glycosylation is essential for processing, localization, stability, and activity of ADAM8.