Isolation of an Isoenzyme of Human Glutaminyl Cyclase: Retention in the Golgi Complex Suggests Involvement in the Protein Maturation Machinery

Role of glutaminyl-peptide cyclo-transferase-like protein (QPCTL) in cancer: From molecular mechanisms to immunotherapy

Glutaminyl-peptide cyclotransferase-like protein (QPCTL) is a newly discovered enzyme that has sparked interest owing to its possible role in cancer genesis and progression. Initially discovered as a post-translational modification regulator of protein maturation, QPCTL has emerged as a key participant in cancer biology. Recent research has linked QPCTL to numerous essential cancer-related processes, including cell proliferation, migration, invasion, and apoptosis. Furthermore, QPCTL expression changes have been seen in a variety of cancer types, underlining its potential as a diagnostic and prognostic marker. The molecular mechanisms behind QPCTL's participation in cancer will be examined in this review. We investigate its involvement in the control of signaling pathways and the modification of cellular activities that are important in cancer. We also examine the clinical importance of QPCTL, including as its relationship with tumor development, metastasis, and response to treatment. We also discuss the possible therapeutic implications of targeting QPCTL in cancer therapy. QPCTL is a prospective target for the development of innovative anticancer treatments due to its participation in several cancer-associated pathways.

Design, synthesis, and evaluation of 4-(4-methyl-4H-1,2,4-triazol-3-yl)piperidine derivatives as potential glutaminyl cyclase isoenzyme inhibitors for the treatment of cancer

Upregulated glutaminyl cyclase isoenzyme (isoQC) contributes to cancer development by catalyzing pE-CD47 generation and thus enhancing CD47-SIRPα binding and subsequent "don't eat me" signals. We thus consider that isoQC could represent a novel target for cancer therapy. We previously prepared a series of diphenyl conjugated imidazole derivatives (DPCIs) and evaluated their use as glutaminyl cyclase (QC) inhibitors. Here, a new series of DPCIs was rationally designed and synthesized. As anticipated, the analogues exhibited considerably improved inhibitory potency against both QC and isoQC. Crucially, these chemicals exhibited marked selectivity toward isoQC. Further assessments established that one selected compound (27) did not affect the viability of A549, H1299, PC9, or HEK293T cells or the body weight of mice. This compound did, however, reduce pE-CD47 levels in infected A549 cells (isoQC_OE and isoQC_KD) and exhibited apparent anti-cancer effects in vivo by downregulating the level of pE-CD47 via the inhibition of isoQC activity. Taken together, these findings indicated that the compounds synthesized in this study could represent potential QC/isoQC inhibitors for the treatment of cancers.

Targeting QPCTL: An Emerging Therapeutic Opportunity

Glutaminyl cyclases, including glutaminyl-peptide cyclotransferase (QPCT) and glutaminyl-peptide cyclotransferase-like protein (QPCTL), primarily catalyze the cyclization of N-terminal glutamine or glutamate to pyroglutamate (pGlu). QPCTL, in particular, modifies the N-terminus of CD47, thereby regulating its interaction with signal-regulatory protein alpha (SIRPα) and modulating phagocytosis of tumor cells by immune cells. Additionally, QPCTL cyclizes the N-termini of CCL2, CCL7, and CX3CL1, influencing the tumor microenvironment and inflammatory responses in cancer and other disorders. Consequently, QPCTL is considered a valuable therapeutic target for several human diseases. However, the development of QPCTL inhibitors remains in its early stages. This perspective summarizes the structural features, catalytic mechanisms, and biological functions of QPCTL, along with its recent advances in small-molecule inhibitors. It provides valuable insights into the development of novel QPCTL inhibitors.

Identification of benzimidazole-6-carboxamide based inhibitors of secretory glutaminyl cyclase for the treatment of Alzheimer's disease

The formation of the pyroglutamate variant of amyloid beta (pGlu-Aβ), which is extremely hydrophobic, rapidly aggregating, and highly neurotoxic, is mediated by the action of secretory glutaminyl cyclase (sQC). The pGlu-Aβ often acts as a seed for the aggregation of the full length Aβ and contributes to the overall load of Aβ plaques in Alzheimer's disease (AD). Therefore, inhibiting sQC is a potential approach to limit the formation of pGlu-Aβ and to modify the progression of AD. This study presents two novel molecules containing benzimidazole-6-carboxamide, namely LSB-09 and LSB-24, as promising sQC inhibitors. These inhibitors demonstrated moderate toxicity in human neuroblastoma cell lines and possessed IC50 values in the micromolar range (40 and 4 μM for LSB-09 and LSB-24, respectively). Additionally, the X-ray crystal structure of the sQC-LSB-09 complex revealed a unique binding mode, and a systematic computational investigation elucidated the binding mode for LSB-24. The binding mode of these two benzimidazole-6-carboxamide inhibitors offers a potential platform for designing attractive lead candidates against sQC.

Focal Cerebral Ischemia Induces Expression of Glutaminyl Cyclase along with Downstream Molecular and Cellular Inflammatory Responses

Glutaminyl cyclase (QC) and its isoenzyme (isoQC) catalyze the formation of N-terminal pyroglutamate (pGlu) from glutamine on a number of neuropeptides, peptide hormones and chemokines. Chemokines of the C-C ligand (CCL) motif family are known to contribute to inflammation in neurodegenerative conditions. Here, we used a model of transient focal cerebral ischemia to explore functional, cellular and molecular responses to ischemia in mice lacking genes for QC, isoQC and their substrate CCL2. Mice of the different genotypes were evaluated for functional consequences of stroke, infarct volume, activation of glia cells, and for QC, isoQC and CCL2 expression. The number of QC-immunoreactive, but not of isoQC-immunoreactive, neurons increased robustly in the infarct area at 24 and 72 h after ischemia. In parallel, immunohistochemical signals for the QC substrate CCL2 increased from 24 to 72 h after ischemia induction without differences between genotypes analyzed. The increase in CCL2 was accompanied by morphological activation of Iba1-immunoreactive microglia and recruitment of MHC-II-positive cells at 72 h after ischemia. Among other chemokines quantified in the brain tissue, CCL17 showed higher concentrations at 72 h compared to 24 h after ischemia. Collectively, these data suggest a critical role for QC in inflammatory processes in the stroke-affected brain.

Metal Ion Binding to Human Glutaminyl Cyclase: A Structural Perspective

Glutaminyl-peptide cyclotransferases (QCs) convert the N-terminal glutamine or glutamate residues of protein and peptide substrates into pyroglutamate (pE) by releasing ammonia or a water molecule. The N-terminal pE modification protects peptides/proteins against proteolytic degradation by amino- or exopeptidases, increasing their stability. Mammalian QC is abundant in the brain and a large amount of evidence indicates that pE peptides are involved in the onset of neural human pathologies such as Alzheimer's and Huntington's disease and synucleinopathies. Hence, human QC (hQC) has become an intensively studied target for drug development against these diseases. Soon after its characterization, hQC was identified as a Zn-dependent enzyme, but a partial restoration of the enzyme activity in the presence of the Co(II) ion was also reported, suggesting a possible role of this metal ion in catalysis. The present work aims to investigate the structure of demetallated hQC and of the reconstituted enzyme with Zn(II) and Co(II) and their behavior in the presence of known inhibitors. Furthermore, our structural determinations provide a possible explanation for the presence of the mononuclear metal binding site of hQC, despite the presence of the same conserved metal binding motifs present in distantly related dinuclear aminopeptidase enzymes.

X-ray Structure-Guided Discovery of a Potent Benzimidazole Glutaminyl Cyclase Inhibitor That Shows Activity in a Parkinson's Disease Mouse Model

The secretory glutaminyl cyclase (sQC) and Golgi-resident glutaminyl cyclase (gQC) are responsible for N-terminal protein pyroglutamation and associated with various human diseases. Although several sQC/gQC inhibitors have been reported, only one inhibitor, PQ912, is currently undergoing clinic trials for the treatment of Alzheimer's disease. We report an X-ray crystal structure of sQC complexed with PQ912, revealing that the benzimidazole makes "anchor" interactions with the active site zinc ion and catalytic triad. Structure-guided design and optimization led to a series of new benzimidazole derivatives exhibiting nanomolar inhibition for both sQC and gQC. In a MPTP-induced Parkinson's disease (PD) mouse model, BI-43 manifested efficacy in mitigating locomotor deficits through reversing dopaminergic neuronal loss, reducing microglia, and decreasing levels of the sQC/gQC substrates, α-synuclein, and CCL2. This study not only offers structural basis and new leads for drug discovery targeting sQC/gQC but also provides evidence supporting sQC/gQC as potential targets for PD treatment.

Isoglutaminyl Cyclase Overexpression Enhances KYSE30 Cancer Cell Proliferation and Migration via the MAPK Signaling Pathway

To understand how upregulated isoglutaminyl cyclase (isoQC) is involved in the initiation of diseases such as cancer, we developed a human KYSE30 carcinoma cell model in which isoQC was stably overexpressed. GO and KEGG analysis of the DEGs (228) and DEPs (254) respectively implicated isoQC on the proliferation invasion and metastasis of cells and suggested that isoQC might participate in the regulation of MAPK, RAS, circadian rhythm, and related pathways. At the functional level, isoQC-overexpressing KYSE30 cells showed enhanced proliferation, migration, and invasion capacity. Next, we decided to study the precise effect of isoQC overexpression on JNK, p-JNK, AKT, p-AKT, ERK, p-ERK, and PER2, as RNA levels of these proteins are significantly correlated with signal levels indicated in RNA-Seq analysis, and these candidates are the top correlated DEPs enriched in RT-qPCR analysis. We saw that only p-ERK expression was inhibited, while PER2 was increased. These phenotypes were inhibited upon exposure to PER2 inhibitor KL044, which allowed for the restoration of p-ERK levels. These data support upregulated isoQC being able to promote cancer cell proliferation and migration in vitro, likely by helping to regulate the MAPK and RAS signaling pathways, and the circadian protein PER2 might be a potential mediator.

Targeting CD47-SIRPα axis for Hodgkin and non-Hodgkin lymphoma immunotherapy

The interaction between cluster of differentiation 47 (CD47) and signal regulatory protein α (SIRPα) protects healthy cells from macrophage attack, which is crucial for maintaining immune homeostasis. Overexpression of CD47 occurs widely across various tumor cell types and transmits the "don't eat me" signal to macrophages to avoid phagocytosis through binding to SIRPα. Blockade of the CD47-SIRPα axis is therefore a promising approach for cancer treatment. Lymphoma is the most common hematological malignancy and is an area of unmet clinical need. This review mainly described the current strategies targeting the CD47-SIRPα axis, including antibodies, SIRPα Fc fusion proteins, small molecule inhibitors, and peptides both in preclinical studies and clinical trials with Hodgkin lymphoma and non-Hodgkin lymphoma.

Therapeutic potential of glutaminyl cyclases: Current status and emerging trends

Glutaminyl cyclase (QC) activity has been identified as a key effector in distinct biological processes. Human glutaminyl-peptide cyclotransferase (QPCT) and glutaminyl-peptide cyclotransferase-like (QPCTL) are considered attractive therapeutic targets in many human disorders, such as neurodegenerative diseases, and a range of inflammatory conditions, as well as for cancer immunotherapy, because of their capacity to modulate cancer immune checkpoint proteins. In this review, we explore the biological functions and structures of QPCT/L enzymes and highlight their therapeutic relevance. We also summarize recent developments in the discovery of small-molecule inhibitors targeting these enzymes, including an overview of preclinical and clinical studies.

Deciphering the role of QPCTL in glioma progression and cancer immunotherapy

Background

Glioma is the most lethal and most aggressive brain cancer, and currently there is no effective treatment. Cancer immunotherapy is an advanced therapy by manipulating immune cells to attack cancer cells and it has been studied a lot in glioma treatment. Targeting the immune checkpoint CD47 or blocking the CD47-SIRPα axis can effectively eliminate glioma cancer cells but also brings side effects such as anemia. Glutaminyl-peptide cyclotransferase-like protein (QPCTL) catalyzes the pyroglutamylation of CD47 and is crucial for the binding between CD47 and SIRPα. Further study found that loss of intracellular QPCTL limits chemokine function and reshapes myeloid infiltration to augment tumor immunity. However, the role of QPCTL in glioma and the relationship between its expression and clinical outcomes remains unclear. Deciphering the role of QPCTL in glioma will provide a promising therapy for glioma cancer immunotherapy.

Methods

QPCTL expression in glioma tissues and normal adjacent tissues was primarily analyzed in The Cancer Genome Atlas (TCGA) database, and further validated in another independent cohort from the Gene Expression Omnibus (GEO) database, Chinese Glioma Genome Atlas (CGGA), and Human Protein Atlas (HPA). The relationships between QPCTL expression and clinicopathologic parameters and overall survival (OS) were assessed using multivariate methods and Kaplan-Meier survival curves. And the proteins network with which QPCTL interacted was built using the online STRING website. Meanwhile, we use Tumor Immune Estimation Resource (TIMER) and Gene Expression Profiling Interactive Analysis (GEPIA) databases to investigate the relationships between QPCTL expression and infiltrated immune cells and their corresponding gene marker sets. We analyzed the Differentially Expressed Genes (DEGs) including GO/KEGG and Gene Set Enrichment Analysis (GSEA) based on QPCTL-high and -low expression tumors.

Results

In contrast to normal tissue, QPCTL expression was higher in glioma tumor tissue (p < 0.05). Higher QPCTL expression was closely associated with high-grade malignancy and advanced tumor stage. Univariate and multivariate analysis indicated the overall survival of glioma patients with higher QPCTL expression is shorter than those with lower QPCTL expression (p < 0.05). Glioma with QPCTL deficiency presented the paucity of infiltrated immune cells and their matching marker sets. Moreover, QPCTL is essential for glioma cell proliferation and tumor growth and is a positive correlation with glioma cell stemness.

Conclusion

High QPCTL expression predicts high grades of gliomas and poor prognosis with impaired infiltration of adaptive immune cells in the tumor microenvironment as well as higher cancer stemness. Moreover, targeting QPCTL will be a promising immunotherapy in glioma cancer treatment.

Is the new angel better than the old devil? Challenges and opportunities in CD47- SIRPα-based cancer therapy

The efficacy of immunotherapies is limited due to the impenetrable nature of the tumor microenvironment (TME). The TME of many tumors is immune-privileged, thus allowing them to evade host immunosurveillance. One mechanism through which this occurs is via the overexpression of CD47, a 'don't eat me' protein that can interact with SIRPα on myeloid cells to suppress their phagocytic action. In recent times, many studies are focusing on CD47-SIRPα-dependent immunotherapies to incite a 'seek and eat' interaction between phagocytes and tumors. Thus, in this review, we highlight the basic molecular properties and mechanisms of CD47-SIRPα cascade. In addition, we discuss the major challenges and potential remedies associated with CD47-SIRPα-based immunotherapies.

Upregulation of Glutaminyl Cyclase Contributes to ERS-Induced Apoptosis in PC12 Cells

Glutaminyl cyclase (QC) is responsible for converting the N-terminal glutaminyl and glutamyl of the proteins into pyroglutamate (pE) through cyclization. It has been confirmed that QC catalyzes the formation of neurotoxic pE-modified Aβ in the brain of AD patients. But the effects of upregulated QC in diverse diseases have not been much clear until recently. Here, RNA sequencing was applied to identify differentially expressed genes (DEGs) in PC12 cells with QC overexpressing or knockdown. A total of 697 DEGs were identified in QC overexpressing cells while only 77 in QC knockdown cells. Multiple bioinformatic approaches revealed that the DEGs in QC overexpressing group were enriched in endoplasmic reticulum stress (ERS) related signaling pathways. The gene expression patterns of 23 DEGs were confirmed by RT-qPCR, in which the genes related to ERS showed the highest consistency. We also revealed the protein levels of GRP78, PERK, CHOP, and PARP-1, and caspase family was significantly upregulated by overexpressing QC. Moreover, overexpressing QC significantly increased apoptosis of PC12 cells in a time dependent manner. However, no significant alteration was observed in QC knockdown cells. Therefore, our study indicated that upregulated QC could induce ERS and apoptosis, which consequently trigger diseases by catalyzing the generation of pE-modified mediators.

2-Amino-1,3,4-thiadiazoles as Glutaminyl Cyclases Inhibitors Increase Phagocytosis through Modification of CD47-SIRPα Checkpoint

Glutaminyl cyclases (QC, isoQC) convert N-terminal glutamine or glutamate into pyroglutamate (pGlu) on substrates. IsoQC has recently been demonstrated to promote pGlu formation on the N-terminus of CD47, the SIRPα binding site, contributing to the "don't eat me" cancer immune signaling of CD47-SIRPα. We developed new QC inhibitors by applying a structure-based optimization approach starting from fragments identified through library screening. Screening of metal binding fragments identified 5-(1H-benzimidazol-5-yl)-1,3,4-thiadiazol-2-amine (9) as a potent fragment, and further modification provided 5-(1-(3-methoxy-4-(3-(piperidin-1-yl)propoxy)benzyl)-1H-benzo[d]imidazol-5-yl)-1,3,4-thiadiazol-2-amine (22b) as a potent QC inhibitor. Treatment with 22b in A549 and H1975 lung cancer cells decreased the CD47/αhCD47-CC2C6 interaction, indicative of the CD47/SIRPα interaction, and enhanced the increased phagocytic activity of both THP-1 and U937 macrophages.

QPCTL regulates macrophage and monocyte abundance and inflammatory signatures in the tumor microenvironment

The enzyme glutaminyl-peptide cyclotransferase-like protein (QPCTL) catalyzes the formation of pyroglutamate residues at the NH₂-terminus of proteins, thereby influencing their biological properties. A number of studies have implicated QPCTL in the regulation of chemokine stability. Furthermore, QPCTL activity has recently been shown to be critical for the formation of the high-affinity SIRPα binding site of the CD47 “don’t-eat-me” protein. Based on the latter data, interference with QPCTL activity —and hence CD47 maturation—may be proposed as a means to promote anti-tumor immunity. However, the pleiotropic activity of QPCTL makes it difficult to predict the effects of QPCTL inhibition on the tumor microenvironment (TME). Using a syngeneic mouse melanoma model, we demonstrate that QPCTL deficiency alters the intra-tumoral monocyte-to-macrophage ratio, results in a profound increase in the presence of pro-inflammatory cancer-associated fibroblasts (CAFs) relative to immunosuppressive TGF-β1-driven CAFs, and leads to an increased IFN and decreased TGF-β transcriptional response signature in tumor cells. Importantly, the functional relevance of the observed TME remodeling is demonstrated by the synergy between QPCTL deletion and anti PD-L1 therapy, sensitizing an otherwise refractory melanoma model to anti-checkpoint therapy. Collectively, these data provide support for the development of strategies to interfere with QPCTL activity as a means to promote tumor-specific immunity.

Bioinformatic analysis identifies potential key genes of epilepsy

Background

Epilepsy is one of the most common brain disorders worldwide. It is usually hard to be identified properly, and a third of patients are drug-resistant. Genes related to the progression and prognosis of epilepsy are particularly needed to be identified.

Methods

In our study, we downloaded the Gene Expression Omnibus (GEO) microarray expression profiling dataset GSE143272. Differentially expressed genes (DEGs) with a fold change (FC) >1.2 and a P-value <0.05 were identified by GEO2R and grouped in male, female and overlapping DEGs. Functional enrichment analysis and Protein-Protein Interaction (PPI) network analysis were performed.

Results

In total, 183 DEGs overlapped (77 ups and 106 downs), 302 DEGs (185 ups and 117 downs) in the male dataset, and 750 DEGs (464 ups and 286 downs) in the female dataset were obtained from the GSE143272 dataset. These DEGs were markedly enriched under various Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) terms. 16 following hub genes were identified based on PPI network analysis: ADCY7, C3AR1, DEGS1, CXCL1 in male-specific DEGs, TOLLIP, ORM1, ELANE, QPCT in female-specific DEGs and FCAR, CD3G, CLEC12A, MOSPD2, CD3D, ALDH3B1, GPR97, PLAUR in overlapping DEGs.

Conclusion

This discovery-driven study may be useful to provide a novel insight into the diagnosis and treatment of epilepsy. However, more experiments are needed in the future to study the functional roles of these genes in epilepsy.

A patent review of glutaminyl cyclase inhibitors (2004-present)

Introduction: Glutaminyl cyclase (QC) enzymes catalyze the post-translational processing of several substrates with N-terminal glutamine or glutamate to form pyroglutamate (pE) residue. In addition to physiological functions, emerging evidence demonstrates that human QCs play a part in pathological processes in diverse diseases such as Alzheimer's disease (AD), inflammatory and cancer diseases.Areas covered: In recent years, efforts to effectively develop QC small-molecule inhibitors have been made and different chemical classes have been disclosed. This review summarizes the patents/applications regarding QC inhibitors released from 2004 (first patent) to now. The patents are mostly described in terms of chemical structures, biochemical/pharmacological activities, and potential clinical applications.Expert opinion: For more than 15 years of research, the knowledge on the QC activity domain has considerably increased and therapeutic potential of QC inhibitors has been explored. An important number of studies and patents have been published to expand the use of QC inhibitors. QC enzymes are pharmacologically interesting targets to be used as an AD-modifying therapy, or for other QC-associated disorder. Distinct classes of chemical scaffolds and potential clinical uses have been claimed by various organizations. For the coming years, there is much to experience in the QC field.

Luteolin promotes macrophage-mediated phagocytosis by inhibiting CD47 pyroglutamation

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Interception of CD47-SIRPα signaling is an elusive yet intriguing goal for anti-tumor immunotherapy since unbiased CD47 blockade by its antibody cannot avoid erythrocyte destruction.

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We previously reported that isoQC, a Golgi-resident enzyme lacking in mature erythrocyte, disrupts the binding of CD47 to SIRPα by downregulating pGlu-CD47 and its interaction with SIRPα (Cell research 2019. 29:502–505).

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In this study, we explored the possibility of utilizing isoQC inhibition to address the challenge of CD47 antibody treatment induced anemia.

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We discovered a new lead compound of isoQC inhibitor, Luteolin, and revealed that posttranslational modification may work as an immunotherapeutic target by abolishing immune checkpoint signaling.

‘Don't eat me’ signal of CD47 is activated via its interaction with SIRPα protein on myeloid cells, especially phagocytic cells, and prevents malignant cells from anti-tumor immunity in which pyroglutamate modification of CD47 by glutaminyl-peptide cyclotransferase-like protein (isoQC) takes an important part evidenced by our previous report that isoQC is an essential regulator for CD47-SIRPα axis with a strong inhibition on macrophage-mediated phagoctyosis. Therefore, we screened for potential isoQC inhibitors by fluorescence-activated cell sorting assay and identified luteolin as a potent compound that blocked the pyroglutamation of CD47 by isoQC. We further demonstrated that luteolin directly bound to isoQC using pull-down assay and isothermal calorimetric (ITC) assay. In consistency, we showed that luteolin markedly abrogated the cell-surface interaction between CD47 and SIRPα in multiple myeloma H929 cells and consequently promoted the macrophage-mediated phagocytosis. Collectively, our study discovered a promising lead compound targeting isoQC, luteolin, which functions distinctly from current CD47 antibody-based drugs and therefore may potentially overcome the clinical side effects associated with CD47 antibody treatment-induced anemia.

Glutaminyl Cyclase, Diseases, and Development of Glutaminyl Cyclase Inhibitors

Pyroglutamate (pE) modification, catalyzed mainly by glutaminyl cyclase (QC), is prevalent throughout nature and is particularly important in mammals including humans for the maturation of hormones, peptides, and proteins. In humans, the upregulation of QC is involved in multiple diseases and conditions including Alzheimer's disease, Huntington's disease, melanomas, thyroid carcinomas, accelerated atherosclerosis, septic arthritics, etc. This upregulation catalyzes the generation of modified mediators such as pE-amyloid beta (Aß) and pE-chemokine ligand 2 (CCL2) peptides. Not surprisingly, QC has emerged as a reasonable target for the development of therapeutics to combat these diseases and conditions. In this manuscript the deleterious effects of upregulated QC resulting in disease manifestation are reviewed, along with progress on the development of QC inhibitors.

Chronic treatment with the (iso-)glutaminyl cyclase inhibitor PQ529 is a novel and effective approach for glomerulonephritis in chronic kidney disease

Glomeruli and renal tubule injury in chronic kidney disease (CKD) is reported to involve induction of macrophage activation through the CCL2/CCR2 axis. The effects of inhibitors of the CCL2/CCR2 axis, such as anti-CCL2 antibody and CCR2 antagonist, on kidney function in animal models or humans with kidney dysfunction have been demonstrated. The N-terminal glutamine on immature CCL2 is replaced with pyroglutamate (pE) by glutaminyl cyclase (QC) and isoQC. pE-CCL2 is stable and resistant to peptidases. We hypothesized that inhibiting QC/isoQC activity would lead to the degradation of CCL2, thereby ameliorating CKD and reducing kidney inflammation. To test this hypothesis, we investigated the renoprotective properties of the QC/isoQC inhibitor PQ529 in anti-glomerular basement membrane (GBM) antibody-induced glomerulonephritis Wistar Kyoto (WKY) rats. Three-week repeated administration of PQ529 (30 and 100 mg/kg, twice daily) significantly reduced the serum and urine CCL2 and urinary protein excretion in a dose-dependent manner. Correlations between the urinary protein level and serum or urinary CCL2 levels were confirmed in tested animals. Repeated administration of PQ529 significantly reduced the expression of CD68, a macrophage marker, in the kidney cortex and mononuclear infiltration into the tubulointerstitium. In addition, decreased levels of urinary KIM-1, β2 microglobulin, and clusterin were detected, suggesting the inhibition of inflammation in both the proximal and distal tubules. These results suggest that PQ529 suppresses the progression of inflammation-induced renal dysfunction by inhibiting the CCL2/CCR2 axis. Inhibition of QC/isoQC may thus be a viable alternative therapeutic approach for treating glomerulonephritis and CKD patients.

A Unique Carboxylic-Acid Hydrogen-Bond Network (CAHBN) Confers Glutaminyl Cyclase Activity on M28 Family Enzymes

Proteins with sequence or structure similar to those of di-Zn exopeptidases are usually classified as the M28-family enzymes, including the mammalian-type glutaminyl cyclases (QCs). QC catalyzes protein N-terminal pyroglutamate formation, a posttranslational modification important under many physiological and pathological conditions, and is a drug target for treating neurodegenerative diseases, cancers and inflammatory disorders. Without functional characterization, mammalian QCs and their orthologs remain indistinguishable at the sequence and structure levels from other M28-family proteins, leading to few reported QCs. Here, we show that a low-barrier carboxylic-acid hydrogen-bond network (CAHBN) is required for QC activity and discriminates QCs from M28-family peptidases. We demonstrate that the CAHBN-containing M28 peptidases deposited in the PDB are indeed QCs. Our analyses identify several thousands of QCs from the three domains of life, and we enzymatically and structurally characterize several. For the first time, the interplay between a CAHBN and the binuclear metal-binding center of mammalian QCs is made clear. We found that the presence or absence of CAHBN is a key discriminator for the formation of either the mono-Zn QCs or the di-Zn exopeptidases. Our study helps explain the possible roles of QCs in life.

Amyloid Beta Hypothesis in Alzheimer's Disease: Major Culprits and Recent Therapeutic Strategies

Alzheimer's disease (AD) is one of the most common forms of dementia and has been a global concern for several years. Due to the multi-factorial nature of the disease, AD has become irreversible, fatal and imposes a tremendous socio-economic burden. Even though experimental medicines suggested moderate benefits, AD still lacks an effective treatment strategy for the management of symptoms or cure. Among the various hypotheses that describe development and progression of AD, the amyloid hypothesis has been a long-term adherent to the AD due to the involvement of various forms of Amyloid beta (Aβ) peptides in the impairment of neuronal and cognitive functions. Hence, majority of the drug discovery approaches in the past have focused on the prevention of the accumulation of Aβ peptides. Currently, there are several agents in the phase III clinical trials that target Aβ or the various macromolecules triggering Aβ deposition. In this review, we present the state of the art knowledge on the functional aspects of the key players involved in the amyloid hypothesis. Furthermore, we also discuss anti-amyloid agents present in the Phase III clinical trials.

Regulation and biological functions of the CX3CL1-CX3CR1 axis and its relevance in solid cancer: A mini-review

CX3CL1 is a transmembrane protein from which a soluble form can be generated by proteolytic shedding. Membranal and soluble forms of CX3CL1 exhibit different functions, although both bind to the CX3CR1 chemokine receptor. The CX3CL1-CX3CR1 axis mediates the adhesion of leukocytes and is also involved in cell survival and recruitment of immune cell subpopulations. The function of CX3CL1 is finely tuned by cytokines and transcription factors regulating its expression and post-translational modifications. On homeostasis, the CX3CL1-CX3CR1 axis participates in the removal of damaged neurons and neurogenesis, and it is also involved on several pathological contexts. The CX3CL1-CX3CR1 axis induces several cellular responses relevant to cancer such as proliferation, migration, invasion and apoptosis resistance. In this review, we address biological aspects of this molecular axis with important therapeutic potential, emphasizing its role in cancer, one of the most prevalent chronic diseases which significantly affect the quality of life and life expectancy of patients.

Piperidine-4-carboxamide as a new scaffold for designing secretory glutaminyl cyclase inhibitors

Alzheimer's disease (AD), a common chronic neurodegenerative disease, has become a major public health concern. Despite years of research, therapeutics for AD are limited. Overexpression of secretory glutaminyl cyclase (sQC) in AD brain leads to the formation of a highly neurotoxic pyroglutamate variant of amyloid beta, pGlu-Aβ, which acts as a potential seed for the aggregation of full length Aβ. Preventing the formation of pGlu-Aβ through inhibition of sQC has become an attractive disease-modifying therapy in AD. In this current study, through a pharmacophore assisted high throughput virtual screening, we report a novel sQC inhibitor (Cpd-41) with a piperidine-4-carboxamide moiety (IC₅₀ = 34 μM). Systematic molecular docking, MD simulations and X-ray crystallographic analysis provided atomistic details of the binding of Cpd-41 in the active site of sQC. The unique mode of binding and moderate toxicity of Cpd-41 make this molecule an attractive candidate for designing high affinity sQC inhibitors.

Regulation of CD47 expression in cancer cells

CD47 is overexpressed in various types of cancers and it can directly bind with SIRPα, which is mainly located on macrophages. The binding of CD47-SIRPα transmits a “don't eat me” signal, which can prevent cancer cells from immune clearance. Targeting the phagocytosis checkpoint of CD47-SIRPα axis has shown remarkable anticancer effect in preclinical and clinical research, which indicates the potential application of CD47-SIRPα blockade for cancer treatment. In this case, the comprehensive description of the regulation of CD47 in different types of cancer cells has significant implications for furthering our understanding of the role of CD47 in cancer. Based on the current reports, we summarized the regulatory factors, i.e., cytokines, oncogenes, microRNAs as well as enzymes, of CD47 expression in cancer cells. Accordingly, we also proposed several points needing further research, hoping to provide useful insights for the future investigation on the regulation of CD47 in cancers.

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Cytokines, oncogenes, microRNAs and enzymes regulate CD47 expression in cancer.

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CD47 expression could be regulated at the transcriptional, post-transcriptional and post-translational modification level.

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Further studies are required to determine other factors that regulate CD47 expression.

Glutaminyl cyclase is an enzymatic modifier of the CD47- SIRPα axis and a target for cancer immunotherapy

Cancer cells can evade immune surveillance through the expression of inhibitory ligands that bind their cognate receptors on immune effector cells. Expression of programmed death ligand 1 in tumor microenvironments is a major immune checkpoint for tumor-specific T cell responses as it binds to programmed cell death protein-1 on activated and dysfunctional T cells¹. The activity of myeloid cells such as macrophages and neutrophils is likewise regulated by a balance between stimulatory and inhibitory signals. In particular, cell surface expression of the CD47 protein creates a 'don't eat me' signal on tumor cells by binding to SIRPα expressed on myeloid cells^2-5. Using a haploid genetic screen, we here identify glutaminyl-peptide cyclotransferase-like protein (QPCTL) as a major component of the CD47-SIRPα checkpoint. Biochemical analysis demonstrates that QPCTL is critical for pyroglutamate formation on CD47 at the SIRPα binding site shortly after biosynthesis. Genetic and pharmacological interference with QPCTL activity enhances antibody-dependent cellular phagocytosis and cellular cytotoxicity of tumor cells. Furthermore, interference with QPCTL expression leads to a major increase in neutrophil-mediated killing of tumor cells in vivo. These data identify QPCTL as a novel target to interfere with the CD47 pathway and thereby augment antibody therapy of cancer.

N-terminal pyroglutamate formation in CX3CL1 is essential for its full biologic activity

CX3CL1 (fractalkine) is a unique member of the CX3C chemokine family and mediates both adhesion and cell migration in inflammatory processes. Frequently, the activity of chemokines depends on a modified N-terminus as described for the N-terminus of CCL2 modified to a pGlu- (pyroglutamate) residue by QC (glutaminyl cyclase) activity. Here, we assess the role of the pGlu-modified residue of the CX3CL1 chemokine domain in human endothelial and smooth muscle cells. For the first time, we demonstrated using MS that QC (QPCT, gene name of QC) or its isoenzyme isoQC (iso-glutaminyl cyclase) (QPCTL, gene name of isoQC) catalyse the formation of N-terminal-modified pGlu-CX3CL1. Expression of QPCT is co-regulated with its substrates CCL2 and CX3CL1 in HUVECs (human umbilical vein endothelial cells) and HCASMCs (human coronary artery smooth muscle cells) upon stimulation with TNF-α and IL-1β whereas QPCTL expression is not affected. By contrast, inhibition of the NF-κB pathway using an IKK2 inhibitor decreased the expression of the co-regulated targets QPCT, CCL2, and CX3CL1. Furthermore, RNAi-mediated inhibition of QPCT expression resulted in a reduction in CCL2 and CX3CL1 mRNA. In HCASMCs, N-terminal-modified pGlu1-CX3CL1 induced a significant stronger effect on phosphorylation of ERK (extracellular signal regulated kinase) 1/2, Akt (protein kinase B), and p38 (p38 mitogen-activated protein kinase) kinases than the immature Gln1-CX3CL1 in a time- and concentration-dependent manner. Furthermore, pGlu1-CX3CL1 affected the expression of CCL2, CX3CL1, and the adhesion molecule ICAM1/CD54 (intercellular adhesion molecule-1) inducing in higher expression level compared with its Gln1-variant in both HCASMCs and HUVECs. These results strongly suggest that QC-catalysed N-terminal pGlu formation of CX3CL1 is important for the stability or the interaction with its receptor and opens new insights into the function of QC in inflammation.

A single transcription factor is sufficient to induce and maintain secretory cell architecture

Here, Lo et al. demonstrate that cell architecture can be controlled by a developmentally regulated transcriptional program independent of the program that specifies cell identity. They show that MIST1 (BHLHA15) is a “scaling factor” that universally establishes secretory morphology in cells that perform regulated secretion, and targeted deletion of MIST1 causes dismantling of the secretory apparatus of diverse exocrine cells.

We hypothesized that basic helix–loop–helix (bHLH) MIST1 (BHLHA15) is a “scaling factor” that universally establishes secretory morphology in cells that perform regulated secretion. Here, we show that targeted deletion of MIST1 caused dismantling of the secretory apparatus of diverse exocrine cells. Parietal cells (PCs), whose function is to pump acid into the stomach, normally lack MIST1 and do not perform regulated secretion. Forced expression of MIST1 in PCs caused them to expand their apical cytoplasm, rearrange mitochondrial/lysosome trafficking, and generate large secretory granules. Mist1 induced a cohort of genes regulated by MIST1 in multiple organs but did not affect PC function. MIST1 bound CATATG/CAGCTG E boxes in the first intron of genes that regulate autophagosome/lysosomal degradation, mitochondrial trafficking, and amino acid metabolism. Similar alterations in cell architecture and gene expression were also caused by ectopically inducing MIST1 in vivo in hepatocytes. Thus, MIST1 is a scaling factor necessary and sufficient by itself to induce and maintain secretory cell architecture. Our results indicate that, whereas mature cell types in each organ may have unique developmental origins, cells performing similar physiological functions throughout the body share similar transcription factor-mediated architectural “blueprints.”

[Molecular mechanisms of pidolate magnesium action and its neurotropic affects]

AIM

A complex study of pharmacological properties of magnesium pyroglutamate using the modern methods of chemoinformatics and bioinformatics.

MATERIAL AND METHODS

Pharmacological properties of magnesium pyroglutamate were studied using chemoinformatic and bioinformatic analyses.

RESULTS

Neurotropic effects of magnesium pyroglutamate are due to an influence on the synthesis of neuropeptides containing pyroglutamate (orexin, thyroliberin, neurotensin etc) and due to the similarity between pyroglutamate-anion with some neuroactive components (L-theanine, 2-pirrolydinone, piracetam).

CONCLUSION

The results of the study suggest neuroprotective, sedative and antidepressive properties of magnesium pyroglutamate which are realized by pyroglutamate-anion in the synergism with magnesium cation.

Identification of Glutaminyl Cyclase Genes Involved in Pyroglutamate Modification of Fungal Lignocellulolytic Enzymes

The breakdown of plant biomass to simple sugars is essential for the production of second-generation biofuels and high-value bioproducts. Currently, enzymes produced from filamentous fungi are used for deconstructing plant cell wall polysaccharides into fermentable sugars for biorefinery applications. A post-translational N-terminal pyroglutamate modification observed in some of these enzymes occurs when N-terminal glutamine or glutamate is cyclized to form a five-membered ring. This modification has been shown to confer resistance to thermal denaturation for CBH-1 and EG-1 cellulases. In mammalian cells, the formation of pyroglutamate is catalyzed by glutaminyl cyclases. Using the model filamentous fungus Neurospora crassa, we identified two genes (qc-1 and qc-2) that encode proteins homologous to mammalian glutaminyl cyclases. We show that qc-1 and qc-2 are essential for catalyzing the formation of an N-terminal pyroglutamate on CBH-1 and GH5-1. CBH-1 and GH5-1 produced in a Δqc-1 Δqc-2 mutant, and thus lacking the N-terminal pyroglutamate modification, showed greater sensitivity to thermal denaturation, and for GH5-1, susceptibility to proteolytic cleavage. QC-1 and QC-2 are endoplasmic reticulum (ER)-localized proteins. The pyroglutamate modification is predicted to occur in a number of additional fungal proteins that have diverse functions. The identification of glutaminyl cyclases in fungi may have implications for production of lignocellulolytic enzymes, heterologous expression, and biotechnological applications revolving around protein stability.

Pyroglutamate modification is the post-translational conversion of N-terminal glutamine or glutamate into a cyclized amino acid derivative. This modification is well studied in animal systems but poorly explored in fungal systems. In Neurospora crassa, we show that this modification takes place in the ER and is catalyzed by two well-conserved enzymes, ubiquitously conserved throughout the fungal kingdom. We demonstrate that the modification is important for the structural stability and aminopeptidase resistance of CBH-1 and GH5-1, two important cellulase enzymes utilized in industrial plant cell wall deconstruction. Many additional fungal proteins predicted in the genome of N. crassa and other filamentous fungi are predicted to carry an N-terminal pyroglutamate modification. Pyroglutamate addition may also be a useful way to stabilize secreted proteins and peptides, which can be easily produced in fungal production systems.

Common variants in QPCT gene confer risk of schizophrenia in the Han Chinese population

Schizophrenia (SCZ) is a common and severe mental disorder, its etiology has not been elucidated completely. In one previous genome-wide association study (GWAS) of SCZ in the Caucasian population, the QPCT has been reported as susceptible gene for SCZ. The QPCT gene encodes Glutaminyl cyclase (QC), an enzyme which is involved in the post translational modification by converting N-terminal glutamate of protein to pyroglutamate, which is resistant to protease degradation, more hydrophobic, and prone to aggregation and neurotoxic. To further investigate the role of this gene in the pathogenesis of schizophrenia in the Han Chinese population, we conducted this study in 1,248 (Mean age ± S.D, 36.44 years ± 9.0) SCZ cases, 1,248 (Mean age ± S.D, 30.62 years ± 11.35) healthy control samples for a case control study. We genotyped six SNPs in this study, including one positive SNP of the previous study, using the Sequenom MassARRAY platform. We found that rs2373000 was significantly associated with SCZ before correction [rs2373000: P allele = 0.016, χ(2)  = 5.784, OR [95%CI] = 0.861 [0.762-0.972], P genotype = 0.018, χ(2)  = 0.069]. After permutation correction for multiple testing, rs2373000 [rs2373000: P Allele corrected = 0.063, P genotype corrected = 0.069] showed marginal association with SCZ. Additionally, one pathogenic haplotype (TGT) containing rs2373000 was also significantly associated with SCZ. Our results are consistent with the findings of previous study and the genetic risk of QPCT gene for SCZ also exists in the Han Chinese population.

Structural Analysis and Aggregation Propensity of Pyroglutamate Aβ(3-40) in Aqueous Trifluoroethanol

A hallmark of Alzheimer's disease (AD) is the accumulation of extracellular amyloid-β (Aβ) plaques in the brains of patients. N-terminally truncated pyroglutamate-modified Aβ (pEAβ) has been described as a major compound of Aβ species in senile plaques. pEAβ is more resistant to degradation, shows higher toxicity and has increased aggregation propensity and β-sheet stabilization compared to non-modified Aβ. Here we characterized recombinant pEAβ(3-40) in aqueous trifluoroethanol (TFE) solution regarding its aggregation propensity and structural changes in comparison to its non-pyroglutamate-modified variant Aβ(1-40). Secondary structure analysis by circular dichroism spectroscopy suggests that pEAβ(3-40) shows an increased tendency to form β-sheet-rich structures in 20% TFE containing solutions where Aβ(1-40) forms α-helices. Aggregation kinetics of pEAβ(3-40) in the presence of 20% TFE monitored by thioflavin-T (ThT) assay showed a typical sigmoidal aggregation in contrast to Aβ(1-40), which lacks ThT positive structures under the same conditions. Transmission electron microscopy confirms that pEAβ(3-40) aggregated to large fibrils and high molecular weight aggregates in spite of the presence of the helix stabilizing co-solvent TFE. High resolution NMR spectroscopy of recombinantly produced and uniformly isotope labeled [U-15N]-pEAβ(3-40) in TFE containing solutions indicates that the pyroglutamate formation affects significantly the N-terminal region, which in turn leads to decreased monomer stability and increased aggregation propensity.

Isoglutaminyl cyclase contributes to CCL2-driven neuroinflammation in Alzheimer's disease

The brains of Alzheimer’s disease (AD) patients are characterized by deposits of Abeta peptides and by accompanying chronic inflammation. Here, we provide evidence that the enzyme isoglutaminyl cyclase (isoQC) is a novel factor contributing to both aspects of AD pathology. Two putative substrates of isoQC, N-truncated Abeta peptides and the monocyte chemoattractant chemokine CCL2, undergo isoQC-catalyzed pyroglutamate (pGlu) modification. This triggers Abeta aggregation and facilitates the biological activity of CCL2, which collectively results in the formation of high molecular weight Abeta aggregates, glial cell activation, neuroinflammation and neuronal cell death. In mouse brain, we found isoQC to be neuron-specifically expressed in neocortical, hippocampal and subcortical structures, localized to the endoplasmic reticulum and Golgi apparatus as well as co-expressed with its substrate CCL2. In aged APP transgenic Tg2576 mice, both isoQC and CCL2 mRNA levels are up-regulated and isoQC and CCL2 proteins were found to be co-induced in Abeta plaque-associated reactive astrocytes. Also, in mouse primary astrocyte culture, a simultaneous up-regulation of isoQC and CCL2 expression was revealed upon Abeta and pGlu-Abeta stimulation. In brains of AD patients, the expression of isoQC and CCL2 mRNA and protein is up-regulated compared to controls and correlates with pGlu-Abeta load and with the decline in mini-mental state examination. Our observations provide evidence for a dual involvement of isoQC in AD pathogenesis by catalysis of pGlu-Abeta and pGlu-CCL2 formation which mutually stimulate inflammatory events and affect cognition. We conclude that isoQC inhibition may target both major pathological events in the development of AD.

Mouse strain and brain region-specific expression of the glutaminyl cyclases QC and isoQC

Glutaminyl cyclases (QCs) catalyze the formation of pyroglutamate (pGlu) from glutamine precursors at the N-terminus of a number of peptide hormones, neuropeptides and chemokines. This post-translational modification stabilizes these peptides, protects them from proteolytical degradation or is important for their biological activity. However, QC is also involved in a pathogenic pGlu modification of peptides accumulating in protein aggregation disorders such as Alzheimer's disease and familial Danish and familial British dementia. Its isoenzyme (isoQC) was shown to contribute to aspects of inflammation by pGlu-modifying and thereby stabilizing the monocyte chemoattractant protein CCL2. For the generation of respective animal models and for pharmacological treatment studies the characterization of the mouse strain and brain region-specific expression of QC and isoQC is indispensible. In order to address this issue, we used enzymatic activity assays and specific antibodies to detect both QC variants by immunohistochemistry in nine different mouse strains. Comparing different brain regions, the highest enzymatic QC/isoQC activity was detected in ventral brain, followed by cortex and hippocampus. Immunohistochemical stainings revealed that QC/isoQC activity in cortex mostly arises from isoQC expression. For most brain regions, the highest QC/isoQC activity was detected in C3H and FVB mice, whereas low QC/isoQC activity was present in CD1, SJL and C57 mice. Quantification of QC- and isoQC-immunoreactive cells by unbiased stereology revealed a higher abundance of isoQC- than of QC-immunoreactive neurons in Edinger-Westphal nucleus and in substantia nigra. In the locus coeruleus, however, there were comparable densities of QC- and of isoQC-immunoreactive neurons. These observations are of considerable importance with regard to the selection of appropriate mouse strains for the study of QC/isoQC relevance in mouse models of neurodegeneration and neuroinflammation and for the testing of therapeutical interventions in these models.

Linked production of pyroglutamate-modified proteins via self-cleavage of fusion tags with TEV protease and autonomous N-terminal cyclization with glutaminyl cyclase in vivo

Overproduction of N-terminal pyroglutamate (pGlu)-modified proteins utilizing Escherichia coli or eukaryotic cells is a challenging work owing to the fact that the recombinant proteins need to be recovered by proteolytic removal of fusion tags to expose the N-terminal glutaminyl or glutamyl residue, which is then converted into pGlu catalyzed by the enzyme glutaminyl cyclase. Herein we describe a new method for production of N-terminal pGlu-containing proteins in vivo via intracellular self-cleavage of fusion tags by tobacco etch virus (TEV) protease and then immediate N-terminal cyclization of passenger target proteins by a bacterial glutaminyl cyclase. To combine with the sticky-end PCR cloning strategy, this design allows the gene of target proteins to be efficiently inserted into the expression vector using two unique cloning sites (i.e., SnaB I and Xho I), and the soluble and N-terminal pGlu-containing proteins are then produced in vivo. Our method has been successfully applied to the production of pGlu-modified enhanced green fluorescence protein and monocyte chemoattractant proteins. This design will facilitate the production of protein drugs and drug target proteins that possess an N-terminal pGlu residue required for their physiological activities.

Structural and functional analyses of a glutaminyl cyclase from Ixodes scapularis reveal metal-independent catalysis and inhibitor binding

Glutaminyl cyclases (QCs) from mammals and Drosophila are zinc-dependent enzymes that catalyze N-terminal pyroglutamate formation of numerous proteins and peptides. These enzymes have been found to be critical for the oviposition and embryogenesis of ticks, implying that they are possible physiological targets for tick control. Here, 1.10-1.15 Å resolution structures of a metal-independent QC from the black-legged tick Ixodes scapularis (Is-QC) are reported. The structures exhibit the typical scaffold of mammalian QCs but have two extra disulfide bridges that stabilize the central β-sheet, resulting in an increased thermal stability. Is-QC contains ~0.5 stoichiometric zinc ions, which could be removed by 1 mM EDTA. Compared with the Zn-bound form, apo-Is-QC has a nearly identical active-site structure and stability, but unexpectedly possesses significantly increased QC activities towards both synthetic and physiological substrates. Enzyme-kinetic analysis revealed that apo-Is-QC has a stronger substrate-binding affinity, suggesting that bound zinc interferes with substrate binding during catalysis. The structures of Is-QC bound to the inhibitor PBD150 revealed similar binding modes to both forms of Is-QC, with the exception of the inhibitor imidazole ring, which is consistent with the comparable inhibition activities of the inhibitor towards both forms of Is-QC. These findings have implications for the design of new QC inhibitors.

Glutaminyl cyclase-mediated toxicity of pyroglutamate-beta amyloid induces striatal neurodegeneration

Background

Posttranslational modifications of beta amyloid (Aβ) have been shown to affect its biophysical and neurophysiological properties. One of these modifications is N-terminal pyroglutamate (pE) formation. Enzymatic glutaminyl cyclase (QC) activity catalyzes cyclization of truncated Aβ(3-x), generating pE3-Aβ. Compared to unmodified Aβ, pE3-Aβ is more hydrophobic and neurotoxic. In addition, it accelerates aggregation of other Aβ species. To directly investigate pE3-Aβ formation and toxicity in vivo, transgenic (tg) ETNA (E at the truncated N-terminus of Aβ) mice expressing truncated human Aβ(3–42) were generated and comprehensively characterized. To further investigate the role of QC in pE3-Aβ formation in vivo, ETNA mice were intercrossed with tg mice overexpressing human QC (hQC) to generate double tg ETNA-hQC mice.

Results

Expression of truncated Aβ(3–42) was detected mainly in the lateral striatum of ETNA mice, leading to progressive accumulation of pE3-Aβ. This ultimately resulted in astrocytosis, loss of DARPP-32 immunoreactivity, and neuronal loss at the sites of pE3-Aβ formation. Neuropathology in ETNA mice was associated with behavioral alterations. In particular, hyperactivity and impaired acoustic sensorimotor gating were detected. Double tg ETNA-hQC mice showed similar Aβ levels and expression sites, while pE3-Aβ were significantly increased, entailing increased astrocytosis and neuronal loss.

Conclusions

ETNA and ETNA-hQC mice represent novel mouse models for QC-mediated toxicity of truncated and pE-modified Aβ. Due to their significant striatal neurodegeneration these mice can also be used for analysis of striatal regulation of basal locomotor activity and sensorimotor gating, and possibly for DARPP-32-dependent neurophysiology and neuropathology. The spatio-temporal correlation of pE3-Aβ and neuropathology strongly argues for an important role of this Aβ species in neurodegenerative processes in these models.

Role of glutaminyl cyclases in thyroid carcinomas

CCL2 is a chemokine known to recruit monocytes/macrophages to sites of inflammation. CCL2 is also associated with tumor progression in several cancer types. Recently, we showed that the N-terminus of CCL2 is modified to a pyroglutamate (pE)-residue by both glutaminyl cyclases (QC (QPCT)) and its isoenzyme (isoQC (QPCTL)). The pE-residue increases stability against N-terminal degradation by aminopeptidases. Here, we report an upregulation of QPCT expression in tissues of patients with thyroid carcinomas compared with goiter tissues, whereas QPCTL was not regulated. In thyroid carcinoma cell lines, QPCT gene expression correlates with the mRNA levels of its substrate CCL2. Both QPCT and CCL2 are regulated in a NF-κB-dependent pathway shown by stimulation with TNFa and IL1b as well as by inhibition with the IKK2 inhibitor and RNAi of p50. In the culture supernatant of thyroid carcinoma cells, equal amounts of pECCL2 and total CCL2 were detected by two ELISAs discriminating between total CCL2 and pECCL2, concluding that all CCL2 is secreted as pECCL2. Activation of the CCL2/CCR2 pathway by recombinant CCL2 increased tumor cell migration of FTC238 cells in scratch assays as well as thyroid carcinoma cell-derived CCL2-induced migration of monocytic THP1 cells. Suppression of CCL2 signaling by CCR2 antagonist, IKK2 inhibitor, and QPCT RNAi reduced FTC238 cell growth measured by WST8 proliferation assays. Our results reveal new evidence for a novel role of QC in thyroid carcinomas and provide an intriguing rationale for the use of QC inhibitors as a means of blocking pECCL2 formation and preventing thyroid cancer metastasis.

Glutaminyl cyclases as novel targets for the treatment of septic arthritis

BACKGROUND

Septic arthritis is a severe and rapidly debilitating disease mainly caused by Staphylococcus aureus. Here, we assess the antiarthritic efficiency of glutaminyl cyclase (QC) inhibitors.

METHODS

Mice were inoculated with an arthritogenic amount of S. aureus intravenously or by local administration into the knee joint. Animals were treated with QC inhibitors (PBD155 and PQ529) via chow during the experiment. QC and isoQC knockout mice were also analyzed for arthritis symptoms after local administration of bacteria.

RESULTS

Both QC inhibitors significantly delayed the onset of clinical signs of arthritis, and inhibitors significantly decreased weight loss in treated animals. Following intraarticular injection of S. aureus, PBD155-treated mice had lower levels of synovitis and bone erosion, as well as less myeloperoxidase in synovial tissue. Fluorescence-activated cell sorter analysis revealed that PBD155 treatment affected the expression pattern of adhesion molecules, preventing the upregulation of cells expressing CD11b/CD18.

CONCLUSION

The compounds investigated here represent a novel class of small molecular antiarthritic inhibitors. In our studies, they exerted strong antiinflammatory actions, and therefore they might be suited for disease-modifying treatment of infectious arthritis.