Simultaneous disturbance of NHE1 and LOXL2 decreases tumorigenicity of head and neck squamous cell carcinoma

OBJECTIVE

Although there have been brilliant advancements in the practical application of therapies targeting immune checkpoints, achieving success in targeting the microenvironment remains elusive. In this study, we aimed to address this gap by focusing on Na+ / H+ exchanger 1 (NHE1) and Lysyl Oxidase Like 2 (LOXL2), which are upregulated in head and neck squamous cell carcinoma (HNSCC) cells.

METHODS

The malignancy of a metastatic human HNSCC cell line was assessed in a mouse tongue cancer xenograft model by knocking down (KD) NHE1, responsible for regulating intracellular pH, and LOXL2, responsible for extracellular matrix (ECM) reorganization via cross-linking of ECM proteins. In addition to assessing changes in PD-L1 levels and collagen accumulation following knockdown, the functional status of the PD-L1 / PD-1 immune checkpoint was examined through co-culture with NK92MI, a PD-1 positive phagocytic human Natural Killer (NK) cell line.

RESULTS

The tumorigenic potential of each single KD cell line was similar to that of the control cells, whereas the potential was attenuated in cells with simultaneous KD of both factors (double knockdown [dKD]). Additionally, we observed decreased PD-L1 levels in NHE1 KD cells and compromised collagen accumulation in LOXL2 KD and dKD cells. NK92MI cells exhibited phagocytic activity toward HNSCC cells in co-culture, and the number of remaining dKD cells after co-culture was the lowest in comparison to the control and single KD cells.

CONCLUSION

This study demonstrated the possibility of achieving efficient anti-tumor effects by simultaneously disturbing multiple factors involved in the modification of the tumor microenvironment.

A Study on the Efficient Preparation of α-Ketoglutarate with L-Glutamate Oxidase

Alpha-ketoglutaric acid (α-KG), as an intermediate product of the tricarboxylic acid cycle, plays a crucial role in peptide and amino acid synthesis. In order to reduce costs and improve efficiency in the oxidative production of α-ketoglutaric acid, this study successfully synthesized and expressed L-glutamate oxidase (LGOXStr) from Streptomyces viridosporus R111 and catalase (KatGEsc) from Escherichia coli H736. Two immobilization methods and the conditions for one-step whole-cell catalysis of α-ketoglutaric acid were investigated. α-Ketoglutaric acid has broad applications in the pharmaceutical, food, and chemical industries. The specific research results are as follows: (1) By fusing the sfGFP tag, L-glutamate oxidase (LGOXStr r) and catalase (KatGEsc) were successfully anchored to the outer membrane of Escherichia coli cells, achieving one-step whole-cell catalysis of α-ketoglutaric acid with a conversion efficiency of up to 75%. (2) Through the co-immobilization of LGOXStr and KatGEsc, optimization of the preparation parameters of immobilized cells, and exploration of the immobilization method using E.coli@ZIF-8, immobilized cells with conversion rates of over 60% were obtained even after 10 cycles of reuse. Under the optimal conditions, the production rate of α-ketoglutaric acid reached 96.7% in a 12 h reaction, which is 1.1 times that of E. coli@SA and 1.29 times that of free cells.

LncRNA LOXL1-AS1 promotes proliferation and invasion and inhibits apoptosis in retinoblastoma by regulating the MAPK signaling pathway

Retinoblastoma (RB) is an intraocular malignancy that is most common in children and rare in adults. Addressing novel biomarkers and therapeutic targets for RB to modulate tumor progression has become a challenge. The aim of the present study was to investigate the function of long non-coding RNAs (LncRNAs) LOXL1-AS1 in RB cell proliferation and metastasis. It was found that LOXL1-AS1 was overexpressed in RB tissues and cells. In order to evaluate cell viability and colony formation potential, the knockdown of LOXL1-AS1 has been established. Knockdown of LOXL1-AS1 was also inhibited cells migration and invasion. In addition, the proportion of cells in the G2/M phase of the sh-LOXL1-AS1 group increased significantly, and the proportion of cells in the sh-NC group decreased significantly. In the xenograft model of RB, the tumors in the sh-LOXL1-AS1 group grow slowly compared to the sh-NC group. Western blot analysis revealed that LOXL1-AS1 can regulate the progression of RB cells through MAPK signaling pathway in vitro and in vivo. These results indicated that LncRNA LOXL1-AS1 promotes proliferation, invasion and inhibits apoptosis of retinoblastoma by regulating MAPK signaling pathway, and might be expected to be a novel basis for clinical diagnosis and treatment.

Neural Wiskott-Aldrich syndrome protein (N-WASP) promotes distant metastasis in pancreatic ductal adenocarcinoma via activation of LOXL2

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive solid malignancies. A specific mechanism of its metastasis has not been established. In this study, we investigated whether Neural Wiskott-Aldrich syndrome protein (N-WASP) plays a role in distant metastasis of PDAC. We found that N-WASP is markedly expressed in clinical patients with PDAC. Clinical analysis showed a notably more distant metastatic pattern in the N-WASP-high group compared to the N-WASP-low group. N-WASP was noted to be a novel mediator of epithelial-mesenchymal transition (EMT) via gene expression profile studies. Knockdown of N-WASP in pancreatic cancer cells significantly inhibited cell invasion, migration, and EMT. We also observed positive association of lysyl oxidase-like 2 (LOXL2) and focal adhesion kinase (FAK) with the N-WASP-mediated response, wherein EMT and invadopodia function were modulated. Both N-WASP and LOXL2 depletion significantly reduced the incidence of liver and lung metastatic lesions in orthotopic mouse models of pancreatic cancer. These results elucidate a novel role for N-WASP signaling associated with LOXL2 in EMT and invadopodia function, with respect to regulation of intercellular communication in tumor cells for promoting pancreatic cancer metastasis. These findings may aid in the development of therapeutic strategies against pancreatic cancer.

Lysine Deacetylation Is a Key Function of the Lysyl Oxidase Family of Proteins in Cancer

Mammalian members of the lysyl oxidase (LOX) family of proteins carry a copper-dependent monoamine oxidase domain exclusively within the C-terminal region, which catalyzes ε-amine oxidation of lysine residues of various proteins. However, recent studies have demonstrated that in LOX-like (LOXL) 2-4 the C-terminal canonical catalytic domain and N-terminal scavenger receptor cysteine-rich (SRCR) repeats domain exhibit lysine deacetylation and deacetylimination catalytic activities. Moreover, the N-terminal SRCR repeats domain is more catalytically active than the C-terminal oxidase domain. Thus, LOX is the third family of lysine deacetylases in addition to histone deacetylase and sirtuin families. In this review, we discuss how the LOX family targets different cellular proteins for deacetylation and deacetylimination to control the development and metastasis of cancer.

Interactions between BRD4S, LOXL2, and MED1 drive cell cycle transcription in triple-negative breast cancer

Triple-negative breast cancer (TNBC) often develops resistance to single-agent treatment, which can be circumvented using targeted combinatorial approaches. Here, we demonstrate that the simultaneous inhibition of LOXL2 and BRD4 synergistically limits TNBC proliferation in vitro and in vivo. Mechanistically, LOXL2 interacts in the nucleus with the short isoform of BRD4 (BRD4S), MED1, and the cell cycle transcriptional regulator B-MyB. These interactions sustain the formation of BRD4 and MED1 nuclear transcriptional foci and control cell cycle progression at the gene expression level. The pharmacological co-inhibition of LOXL2 and BRD4 reduces BRD4 nuclear foci, BRD4-MED1 colocalization, and the transcription of cell cycle genes, thus suppressing TNBC cell proliferation. Targeting the interaction between BRD4S and LOXL2 could be a starting point for the development of new anticancer strategies for the treatment of TNBC.

Reshaping the Substrate Binding Pocket of β-Amino Acid Dehydrogenase for the Synthesis of Aromatic β-Amino Acids

By reshaping the substrate-binding pocket of β-amino acid dehydrogenase (β-AADH), some variants were obtained with up to 2560-fold enhanced activity toward the model substrates (S)-β-homophenylalanine and (R)-β-phenylalanine. A few aromatic β-amino acids were prepared with >99% ee and high isolated yields via either kinetic resolution of racemates or reductive amination of the corresponding β-keto acids. This work expands the catalytic capability of β-AADHs and highlights their practical application in the synthesis of pharmaceutically relevant β-amino acids.

A protein complex of LCN2, LOXL2 and MMP9 facilitates tumour metastasis in oesophageal cancer

During malignant tumour development, the extracellular matrix (ECM) is usually abnormally regulated. Dysregulated expression of lysyl oxidase-like 2 (LOXL2), matrix metalloproteinase 9 (MMP9) and lipocalin 2 (LCN2) are associated with ECM remodelling. In this study, protein-protein interaction assays indicated that LCN2 and LOXL2 interactions and LCN2 and MMP9 interactions occurred both intracellularly and extracellularly, but interactions between LOXL2 and MMP9 only occurred intracellularly. The LCN2/LOXL2/MMP9 ternary complex promoted migration and invasion of oesophageal squamous cell carcinoma (ESCC) cells, as well as tumour growth and malignant progression in vivo, while the iron chelator deferoxamine mesylate (DFOM) inhibited ESCC tumour growth. Co-overexpression of LCN2, LOXL2 and MMP9 enhanced the ability of tumour cells to degrade fibronectin and Matrigel, increased the formation and extension of filopodia, and promoted the rearrangement of microfilaments through upregulation of profilin 1. In addition, the LCN2/LOXL2/MMP9 ternary complex promoted the expression of testican-1 (SPOCK1), and abnormally activated the FAK/AKT/GSK3β signalling pathway. In summary, the LCN2/LOXL2/MMP9 ternary complex promoted the migration and invasion of cancer cells and malignant tumour progression through multiple mechanisms and could be a potential therapeutic target.

Genetic background determines severity of Loxl1-mediated systemic and ocular elastosis in mice

Pseudoexfoliation syndrome (PEX) is a systemic, age-related disorder characterized by elastosis and extracellular matrix deposits. Its most significant ocular manifestation is an aggressive form of glaucoma associated with variants in the gene encoding lysyl oxidase-like 1 (LOXL1). Depending upon the population, variants in LOXL1 can impart risk or protection for PEX, suggesting the importance of genetic context. As LOXL1 protein levels are lower and the degree of elastosis is higher in people with PEX, we studied Loxl1-deficient mice on three different genetic backgrounds: C57BL/6 (BL/6), 129S×C57BL/6 (50/50) and 129S. Early onset and high prevalence of spontaneous pelvic organ prolapse in BL/6 Loxl1-/- mice necessitated the study of mice that were <2 months old. Similar to pelvic organ prolapse, most elastosis endpoints were the most severe in BL/6 Loxl1-/- mice, including skin laxity, pulmonary tropoelastin accumulation, expansion of Schlemm's canal and dilation of intrascleral veins. Interestingly, intraocular pressure was elevated in 50/50 Loxl1-/- mice, depressed in BL/6 Loxl1-/- mice and unchanged in 129S Loxl1-/- mice compared to that of control littermates. Overall, the 129S background was protective against most elastosis phenotypes studied. Thus, repair of elastin-containing tissues is impacted by the abundance of LOXL1 and genetic context in young animals.

The possibilities of LOXL4 as a prognostic marker for carcinomas

Lysyl oxidase-like 4 (LOXL4), a member of lysyl oxidase family, is a copper and lysine tyrosylquinone-dependent amine oxidase that serves the role of catalyzing the cross-linking of elastin and collagen in the extracellular matrix. Numerous studies have shown a significant association between LOXL4 expression levels and tumor proliferation, migration, invasion and patients' prognosis and overall survival in different types of tumors. Here we review their relationship and the molecular pathogenesis behind them, aiming to explore the possibilities of LOXL4 as a prognostic marker for diverse carcinomas and provide some indications for further research in this field.

Computational Insights on the Hydride and Proton Transfer Mechanisms of D-Arginine Dehydrogenase

D-Arginine dehydrogenase from Pseudomonas aeruginosa (PaDADH) is an amine oxidase which catalyzes the conversion of D-arginine into iminoarginine. It contains a non-covalent FAD cofactor that is involved in the oxidation mechanism. Based on substrate, solvent, and multiple kinetic isotope effects studies, a stepwise hydride transfer mechanism is proposed. It was shown that D-arginine binds to the active site of enzyme as α-amino group protonated, and it is deprotonated before a hydride ion is transferred from its α-C to FAD. Based on a mutagenesis study, it was concluded that a water molecule is the most likely catalytic base responsible from the deprotonation of α-amino group. In this study, we formulated computational models based on ONIOM method to elucidate the oxidation mechanism of D-arginine into iminoarginine using the crystal structure of enzyme complexed with iminoarginine. The calculations showed that Arg222, Arg305, Tyr249, Glu87, His 48, and two active site water molecules play key roles in binding and catalysis. Model systems showed that the deprotonation step occurs prior to hydride transfer step, and active site water molecule(s) may have participated in the deprotonation process.

LOXL2 serves as a prognostic biomarker for hepatocellular carcinoma by mediating immune infiltration and vasculogenic mimicry

BACKGROUND

The development of human hepatocellular carcinoma (HCC) is a multistep process that is accompanied by progressive changes in the liver microenvironment, including immune evasion and angiogenesis. Lysyl oxidase-like 2 (LOXL2) has been suggested to contribute to tumour progression and metastasis; however, the underlying mechanism remains unclear. The purpose of the present study was to explore the relationship between LOXL2 and immune infiltration and vasculogenic mimicry (VM) and to identify the role of LOXL2 in HCC diagnosis prognosis evaluation.

METHODS

The Cancer Genome Atlas (TCGA), UALCAN, GEPIA and Kaplan-Meier plotter databases were used to analyse LOXL2 expression and perform survival analysis. The Tumour Immune Estimation Resource (TIMER) was used to analyse immune cell infiltration, immune cell biomarkers and immune checkpoints. Immunohistochemistry (IHC) of 201 HCC samples was used to confirm the expression of LOXL2 and its relationship with VM. Coimmunoprecipitation (co-IP) and gain- and loss-of-function studies were performed to confirm the molecular mechanism of LOXL2 in VM.

RESULTS

The expression of LOXL2 in HCC was higher than that in normal tissues at both the mRNA and protein levels. High expression of LOXL2 was associated with a poorer prognosis of HCC. The genetic alteration rate of LOXL2 was 5%. LOXL2 was positively related to immune cell infiltration and immune checkpoints (PD-1 and CTLA-4) in HCC. Co-IP showed that LOXL2 can interact directly with IQGAP1. Both gain- and loss-of-function studies showed that LOXL2 significantly induced cell migration, invasion and VM formation when IQGAP1 was upregulated.

CONCLUSIONS

LOXL2 is involved in immune cell infiltration and promotes VM by upregulating IQGAP1. LOXL2 can be used as a novel biomarker for HCC diagnosis and prognosis prediction.

Progressive degeneration of the retina in Loxl3 mutant mouse model of Stickler syndrome

Stickler syndrome is a multisystem collagenopathy with affected individuals exhibiting a high rate of ocular complications. Lysyl oxidase-like 3 (LOXL3) is a human disease gene candidate with a critical role in catalyzing collagen crosslinking. A homozygous missense variant of LOXL3 was reported in Stickler syndrome with severe myopia. However, the underlying mechanisms of the LOXL3 missense mutation that causes Stickler syndrome are unknown. In this study, a mouse model of Stickler syndrome induced by LOXL3 mutation (c.2027G ​> ​A, p.Cys676Try) was obtained using CRISPR/Cas9 gene editing techniques. The Loxl3 mutant mice exhibited perinatal death, spinal deformity, and cleft palate, and Loxl3 mutation also induced skeletal dysplasia and progressive visual degeneration. Furthermore, we observed the damage of the bruch's membrane (BrM) and an increase in the levels of glial fibrillary acidic protein (GFAP) and Rpe65 in the Loxl3 mutant mice. Thus, we provided the critical in vivo evidence that Loxl3 possibly has a pivotal role in maintaining the eye function.

LOXL2 reduces 5-FU sensitivity through the Hedgehog/BCL2 signaling pathway in colorectal cancer

Elevated expression of lysyl oxidase-like 2 (LOXL2) contributes to the malignant tumor progression in multiple cancers. However, the role of LOXL2 in the 5-fluorouracil (5-FU) resistance of colorectal cancer (CRC) remains unclear. This study aimed to explore the effects of LOXL2 on 5-FU sensitivity in CRC. The mRNA and protein levels of LOXL2 were explored in public databases by bioinformatics, validated in clinical tissues using immunohistochemistry, and detected in 5-FU treated cell lines. The 50% inhibitory concentrations (IC50) values were quantified based on the cell viability at different concentrations of 5-FU with CCK-8 assays. Colony formation and flow cytometry assays were performed to measure the proliferation and apoptosis rates. Gene set enrichment and correlation analyses were conducted to identify the probable mechanism of LOXL2 in TCGA samples. Critical molecules of the Hedgehog signaling pathway and anti-apoptotic BCL2 in protein levels were detected with Western blotting. It concluded that LOXL2 was up-regulated and positively linked to the unfavorable prognosis of CRC patients. The LOXL2 expression increased with the rising 5-FU concentrations, especially at 20 and 40 μM. Elevated LOXL2 promoted the resistance to 5-FU, augmented the proliferation, and inhibited 5-FU-induced apoptosis of CRC cells. LOXL2 activated the Hedgehog signaling pathway by promoting the expression of SMO, GLI1, and GLI2, leading to the upregulation of downstream target gene BCL2 in CRC cells. Moreover, the Hedgehog signaling pathway inhibitor cyclopamine blocked the BCL2 upregulation mediated by LOXL2. This study has demonstrated that LOXL2 can reduce 5-FU sensitivity through the Hedgehog/BCL2 signaling pathway in CRC.

Up-regulation of long non-coding RNA LOXL1-AS1 functions as an oncogene in cervical squamous cell carcinoma by sponging miR-21

LncRNA LOXL1-AS1 has been reported to be upregulated in several types of cancer and plays oncogenic roles. We analysed TCGA dataset and observed the downregulation of LOXL1-AS1 in cervical squamous cell carcinoma (CSCC). We therefore analysed the roles of LOXL1-AS1 in CSCC. We observed that LOXL1-AS1 was downregulated in CSCC. LOXL1-AS1 was predicted to interact with miR-21, while overexpression experiments showed that LOXL1-AS1 and miR-21 had no significant effects on the expression of each other. However, LOXL1-AS1 overexpression led to the upregulation of RHOB, a direct target of miR-21. Cell invasion and migration analysis showed decreased invasion and migration rates of CSCC cells after LOXL1-AS1 and RHOB overexpression. MiR-21 played an opposite role at reduced the effects of LOXL1-AS1 and RHOB overexpression. Therefore, LOXL1-AS1 may promote CSCC cell invasion and migration by sponging miR-21 to upregulate RHOB.

LncRNA LOXL1-AS1 expression in cancer prognosis: A meta-analysis

BACKGROUND

Several studies showed that LncRNA LOXL1 antisense RNA 1 (LOXL1-AS1) is overexpressed in a variety of cancers and plays a role as an oncogene in cancer. The present meta-analysis aims to elucidate the relationship between LOXL1-AS1 expression and prognosis and clinicopathological features among cancer patients.

METHODS

PubMed, Web of Science, Cochrane Library, and EMBASE database were comprehensively and systematically searched. Pooled odds ratios (ORs) and hazard ratios with a 95% confidence interval (CI) were employed to assess the relationship between LOXL1-AS1 expression and clinical outcomes and clinicopathological features in cancer patients.

RESULTS

The present study finally enrolled 8 studies which included 657 cancer patients. The combined results indicated that the overexpression of LOXL1-AS1 was significantly associated with shorter overall survival (pooled hazard ratio = 1.99, 95% CI 1.49-2.65, P < .00001). Meanwhile, regarding clinicopathology of cancer patients, the upregulation of LOXL1-AS1 expression was closely related to lymph node metastasis (yes vs no OR = 4.01, 95% CI: 2.02-7.96, P < .0001) and distant metastasis (yes vs no OR = 3.04, 95% CI: 1.82-5.06, P < .0001), respectively.

CONCLUSION

High expression of LOXL1-AS1 in some cancers predicts shorter overall survival, distant metastasis, and lymph node metastasis. LOXL1-AS1 shows great promise as a prognostic biomarker in cancer patients.

TRIM44 regulates tumor immunity in gastric cancer through LOXL2-dependent extracellular matrix remodeling

PURPOSE

Gastric cancer is a gastrointestinal malignancy with high mortality and poor prognosis, and the molecular mechanism of gastric tumorigenesis remains unclear. TRIM44 has been reported to be involved in tumor development. However, the role of TRIM44 in tumor immunity is largely unknown.

METHODS

We analyzed TRIM44 expression in clinical gastric cancer tissues and normal tissues by using western blot, quantitative real-time PCR and bioinformatics analyses. We further investigated the involvement of TRIM44 in tumor immunity in vivo and found that it was dependent on extracellular matrix remodeling. We detected the interaction between TRIM44 and LOXL2 by using immunofluorescence staining and coimmunoprecipitation assays. We observed that TRIM44 mediates the stability of LOXL2 by ubiquitination assays.

RESULTS

TRIM44 expression is high and is correlated with T-cell infiltration in gastric cancer. TRIM44 inhibits gastric tumorigenicity by regulating T-cell-mediated antitumor immunity and modulating the protein level of LOXL2. Mechanistically, TRIM44 directly binds to LOXL2 and affects the stability of LOXL2 to change extracellular matrix remodeling and influence tumor immunity.

CONCLUSION

These findings demonstrate that TRIM44 regulates the stability of LOXL2 to remodel the tumor extracellular matrix to modulate tumor immunity in gastric cancer and that the TRIM44/LOXL2 complex is a promising biomarker for gastric cancer prognosis and might be a novel immunotherapy target.

Loss of LOXL2 Promotes Uterine Hypertrophy and Tumor Progression by Enhancing H3K36ac-Dependent Gene Expression

Lysyl oxidase-like 2 (LOXL2) is a member of the scavenger receptor cysteine-rich (SRCR) repeat carrying LOX family. Although LOXL2 is suspected to be involved in histone association and chromatin modification, the role of LOXL2 in epigenetic regulation during tumorigenesis and cancer progression remains unclear. Here, we report that nuclear LOXL2 associates with histone H3 and catalyzes H3K36ac deacetylation and deacetylimination. Both the N-terminal SRCR repeats and the C-terminal catalytic domain of LOXL2 carry redundant deacetylase catalytic activity. Overexpression of LOXL2 markedly reduced H3K36 acetylation and blocked H3K36ac-dependent transcription of genes, including c-MYC, CCND1, HIF1A, and CD44. Consequently, LOXL2 overexpression reduced cancer cell proliferation in vitro and inhibited xenograft tumor growth in vivo. In contrast, LOXL2 deficiency resulted in increased H3K36 acetylation and aberrant expression of H3K36ac-dependent genes involved in multiple oncogenic signaling pathways. Female LOXL2-deficient mice spontaneously developed uterine hypertrophy and uterine carcinoma. Moreover, silencing LOXL2 in cancer cells enhanced tumor progression and reduced the efficacy of cisplatin and anti-programmed cell death 1 (PD-1) combination therapy. Clinically, low nuclear LOXL2 expression and high H3K36ac levels corresponded to poor prognosis in uterine endometrial carcinoma patients. These results suggest that nuclear LOXL2 restricts cancer development in the female reproductive system via the regulation of H3K36ac deacetylation.

SIGNIFICANCE

LOXL2 loss reprograms the epigenetic landscape to promote uterine cancer initiation and progression and repress the efficacy of anti-PD-1 immunotherapy, indicating that LOXL2 is a tumor suppressor.

LncRNA CFAR promotes cardiac fibrosis via the miR-449a-5p/LOXL3/mTOR axis

Cardiac fibrosis is one of the crucial pathological factors in the heart, and various cardiac conditions associated with excessive fibrosis can eventually lead to heart failure. However, the exact molecular mechanism of cardiac fibrosis remains unclear. In the present study, we show that a novel lncRNA that we named cardiac fibrosis-associated regulator (CFAR) is a profibrotic factor in the heart. CFAR was upregulated in cardiac fibrosis and its knockdown attenuated the expression of fibrotic marker genes and the proliferation of cardiac fibroblasts, thereby ameliorating cardiac fibrosis. Moreover, CFAR acted as a ceRNA sponge for miR-449a-5p and derepressed the expression of LOXL3, which we experimentally established as a target gene of miR-449a-5p. In contrast to CFAR, miR-449a-5p was found to be significantly downregulated in cardiac fibrosis, and artificial knockdown of miR-449a-5p exacerbated fibrogenesis, whereas overexpression of miR-449a-5p impeded fibrogenesis. Furthermore, we found that LOXL3 mimicked the fibrotic factor TGF-β1 to promote cardiac fibrosis by activating mTOR. Collectively, our study established CFAR as a new profibrotic factor acting through a novel miR-449a-5p/LOXL3/mTOR axis in the heart and therefore might be considered as a potential molecular target for the treatment of cardiac fibrosis and associated heart diseases.

LOXL3-promoted hepatocellular carcinoma progression via promotion of Snail1/USP4-mediated epithelial-mesenchymal transition

Lysyl-oxidase-like 3 (LOXL3) was reported to be essential in epithelial-mesenchymal transition (EMT) of cancers. However, the role of LOXL3 in hepatocellular carcinoma (HCC) remained unclear. In this study, we explored clinical significance, biological functions, and regulatory mechanisms of LOXL3 in HCC. Our study found that LOXL3 expression was markedly associated with the tumor size and clinical stage of HCC, and it was highly expressed in tumor tissues of metastatic HCC patients. High expression of LOXL3 predicted a poor prognosis of HCC. TGF-β1 treatment elevated LOXL3 protein expression and cell invasion, and reduced cell apoptosis in HCC cell lines (SMMC-7721 and Huh-7), while downregulation of LOXL3 reversed the promotive effects of TGF-β1 treatment on LOXL3 protein expression and cell invasion, and the inhibitory effect on cell apoptosis. Mechanistically, LOXL3 interacted with snail family transcriptional repressor 1 (Snail1) through STRING database and RIP assay, and Snail1 bound to ubiquitin-specific peptidase 4 (USP4) promoter by JASPAR database, luciferase reporter gene and Co-IP assays. Overexpression of USP4 reversed the inhibitory effect of LOXL3 silence on EMT in HCC cells through deubiquitinating and stabilizing the expression of Snail1. Moreover, LOXL3-promoted HCC EMT through Wnt/β-catenin/Snail1 signaling pathway. In vivo study revealed that silence of LOXL3-inhibited HCC tumor growth. In conclusion, LOXL3 silence inhibited HCC invasion and EMT through Snail1/USP4-mediated circulation loop and Wnt/β-catenin signaling pathway.

Knock-Out of the Five Lysyl-Oxidase Family Genes Enables Identification of Lysyl-Oxidase Pro-Enzyme Regulated Genes

The five lysyl-oxidase genes share similar enzymatic activities and contribute to tumor progression. We have knocked out the five lysyl-oxidase genes in MDA-MB-231 breast cancer cells using CRISPR/Cas9 in order to identify genes that are regulated by LOX but not by other lysyl-oxidases and in order to study such genes in more mechanistic detail in the future. Re-expression of the full-length cDNA encoding LOX identified four genes whose expression was downregulated in the knock-out cells and rescued following LOX re-expression but not re-expression of other lysyl-oxidases. These were the AGR2, STOX2, DNAJB11 and DNAJC3 genes. AGR2 and STOX2 were previously identified as promoters of tumor progression. In addition, we identified several genes that were not downregulated in the knock-out cells but were strongly upregulated following LOX or LOXL3 re-expression. Some of these, such as the DERL3 gene, also promote tumor progression. There was very little proteolytic processing of the re-expressed LOX pro-enzyme in the MDA-MB-231 cells, while in the HEK293 cells, the LOX pro-enzyme was efficiently cleaved. We introduced point mutations into the known BMP-1 and ADAMTS2/14 cleavage sites of LOX. The BMP-1 mutant was secreted but not cleaved, while the LOX double mutant dmutLOX was not cleaved or secreted. However, even in the presence of the irreversible LOX inhibitor β-aminoproprionitrile (BAPN), these point-mutated LOX variants induced the expression of these genes, suggesting that the LOX pro-enzyme has hitherto unrecognized biological functions.

Correlation of Matrisome-Associatted Gene Expressions with LOX Family Members in Astrocytomas Stratified by IDH Mutation Status

Tumor cell infiltrative ability into surrounding brain tissue is a characteristic of diffusely infiltrative astrocytoma and is strongly associated with extracellular matrix (ECM) stiffness. Collagens are the most abundant ECM scaffolding proteins and contribute to matrix organization and stiffness. LOX family members, copper-dependent amine oxidases, participate in the collagen and elastin crosslinking that determine ECM tensile strength. Common IDH mutations in lower-grade gliomas (LGG) impact prognosis and have been associated with ECM stiffness. We analyzed the expression levels of LOX family members and matrisome-associated genes in astrocytoma stratified by malignancy grade and IDH mutation status. A progressive increase in expression of all five LOX family members according to malignancy grade was found. LOX, LOXL1, and LOXL3 expression correlated with matrisome gene expressions. LOXL1 correlations were detected in LGG with IDH mutation (IDH^mut), LOXL3 correlations in LGG with IDH wild type (IDH^wt) and strong LOX correlations in glioblastoma (GBM) were found. These increasing correlations may explain the increment of ECM stiffness and tumor aggressiveness from LGG-IDH^mut and LGG-IDH^wt through to GBM. The expression of the mechanosensitive transcription factor, β-catenin, also increased with malignancy grade and was correlated with LOXL1 and LOXL3 expression, suggesting involvement of this factor in the outside–in signaling pathway.

HucMSCs-exosomes containing miR-21 promoted estrogen production in ovarian granulosa cells via LATS1-mediated phosphorylation of LOXL2 and YAP

BACKGROUND

Premature ovarian failure (POF) is one of the common disorders found in women leading to 1% female infertility. Clinical features of POF are hypoestrogenism or estrogen deficiency. With the development of regenerative medicine, human mesenchymal stem cells (hMSCs) therapy brings new prospects for POF. This research aims to reveal the therapeutic effects and potential mechanisms of human umbilical cord mesenchymal stem cells (hucMSCs)-derived exosomes on POF.

METHODS

The mRNA and protein expressions in hucMSCs and ovarian granulosa cells (KGN and SVOG cells) were assessed using qRT-PCR and western blot. ELISA assay was performed to evaluate estradiol (E2) secretion in granulosa cells. The binding relationship between miR-21 and LATS1 was verified by dual-luciferase reporter assay and RNA binding protein immunoprecipitation assay (RIP) assay. Additionally, Immunoprecipitation assay was carried out to confirm Lysyl oxidase like 2 (LOXL2) was phosphorylated by large tumor suppressor 1 (LATS1). Finally, the binding relationships between Yes-associated protein (YAP), StAR and LOXL2 were verified by dual-luciferase reporter assay and/or chromatin immunoprecipitation assay (ChIP) assay.

RESULTS

Here our results displayed that miR-21 was overexpressed in hucMSCs and hucMSCs-derived exosomes, compared with that ovarian granulosa cells. hucMSC-exo with overexpressing miR-21 could markedly promote the secretion of estrogen in ovarian granulosa cells. LATS1 overexpression in ovarian granulosa cells reduced the secretion of estrogen. We subsequently confirmed that LATS1 was the target of miR-21. In addition, LATS1 could regulate StAR expression by phosphorylating LOXL2 and YAP.

CONCLUSION

miR-21 carried by hucMSCs-derived exosomes could downregulate LATS1, thereby reducing phosphorylated LOXL2 and YAP, and ultimately promoting estrogen secretion in ovarian granulosa cells.

Recharacterization of the Mammalian Cytosolic Type 2 (R)-β-Hydroxybutyrate Dehydrogenase (BDH2) as 4-Oxo-L-Proline Reductase (EC 1.1.1.104)

Early studies revealed that chicken embryos incubated with a rare analog of l-proline, 4-oxo-l-proline, showed increased levels of the metabolite 4-hydroxy-l-proline. In 1962, 4-oxo-l-proline reductase, an enzyme responsible for the reduction of 4-oxo-l-proline, was partially purified from rabbit kidneys and characterized biochemically. However, only recently was the molecular identity of this enzyme solved. Here, we report the purification from rat kidneys, identification, and biochemical characterization of 4-oxo-l-proline reductase. Following mass spectrometry analysis of the purified protein preparation, the previously annotated mammalian cytosolic type 2 (R)-β-hydroxybutyrate dehydrogenase (BDH2) emerged as the only candidate for the reductase. We subsequently expressed rat and human BDH2 in Escherichia coli, then purified it, and showed that it catalyzed the reversible reduction of 4-oxo-l-proline to cis-4-hydroxy-l-proline via chromatographic and tandem mass spectrometry analysis. Specificity studies with an array of compounds carried out on both enzymes showed that 4-oxo-l-proline was the best substrate, and the human enzyme acted with 12,500-fold higher catalytic efficiency on 4-oxo-l-proline than on (R)-β-hydroxybutyrate. In addition, human embryonic kidney 293T (HEK293T) cells efficiently metabolized 4-oxo-l-proline to cis-4-hydroxy-l-proline, whereas HEK293T BDH2 KO cells were incapable of producing cis-4-hydroxy-l-proline. Both WT and KO HEK293T cells also produced trans-4-hydroxy-l-proline in the presence of 4-oxo-l-proline, suggesting that the latter compound might interfere with the trans-4-hydroxy-l-proline breakdown in human cells. We conclude that BDH2 is a mammalian 4-oxo-l-proline reductase that converts 4-oxo-l-proline to cis-4-hydroxy-l-proline and not to trans-4-hydroxy-l-proline, as originally thought. We also hypothesize that this enzyme may be a potential source of cis-4-hydroxy-l-proline in mammalian tissues.

Editing of 1-aminocyclopropane-1-carboxylate oxidase genes negatively affects petunia seed germination

Editing of ACO genes involved in ethylene biosynthesis pathway reduces ethylene production in petunia seeds and inhibits seed germination. Ethylene production in the seeds of Petunia hybrida cv. 'Mirage Rose' was associated with expression of 1-aminocyclopropane-1-carboxylic acid (ACC) oxidase (ACO) genes (PhACO1, PhACO3, and PhACO4). Suppression of their expression by ethylene inhibitor silver thiosulphate (STS) significantly reduced ethylene production and inhibited seed germination. When it was combined with ethylene precursor ACC, ethylene production was re-promoted via activation of the genes and higher seed germination was restored. This was confirmed using the mutants editing the genes and WT. In the present study, compared with wild type plants, three different mutants (phaco1, phaco3, and phaco4) showed significantly decreased germination percentages as well as delayed germination time and seedling growth. These reductions were associated with lighter seed weight, lower ACO transcript levels, and lower ethylene production in mutants. Inhibited seed germination owing to reduced ethylene production was further verified by the supplementation of exogenous ACC and gibberellic acid (GA₃) to growth medium, which restored high seed germination activity in all mutants via enhanced ethylene production. In this study, we reported a key regulatory role of ethylene in seed germination mechanisms in petunia. Further, we highlighted on need to consider the negative effects of ethylene reduction in seed germination and plant growth when editing genes in the ethylene biosynthesis pathway for the maintenance of postharvest fruit, vegetable, and flower quality.

Oligomeric States and Hydrodynamic Properties of Lysyl Oxidase-Like 2

Lysyl oxidase-like 2 (LOXL2) has emerged as a promising therapeutic target against metastatic/invasive tumors and organ and tissue fibrosis. LOXL2 catalyzes the oxidative deamination of lysine and hydroxylysine residues in extracellular matrix (ECM) proteins to promote crosslinking of these proteins, and thereby plays a major role in ECM remodeling. LOXL2 secretes as 100-kDa full-length protein (fl-LOXL2) and then undergoes proteolytic cleavage of the first two scavenger receptor cysteine-rich (SRCR) domains to yield 60-kDa protein (Δ1-2SRCR-LOXL2). This processing does not affect the amine oxidase activity of LOXL2 in vitro. However, the physiological importance of this cleavage still remains elusive. In this study, we focused on characterization of biophysical properties of fl- and Δ1-2SRCR-LOXL2s (e.g., oligomeric states, molecular weights, and hydrodynamic radii in solution) to gain insight into the structural role of the first two SRCR domains. Our study reveals that fl-LOXL2 exists predominantly as monomer but also dimer to the lesser extent when its concentration is <~1 mM. The hydrodynamic radius (R_h) determined by multi-angle light scattering coupled with size exclusion chromatography (SEC-MALS) indicates that fl-LOXL2 is a moderately asymmetric protein. In contrast, Δ1-2SRCR-LOXL2 exists solely as monomer and its R_h is in good agreement with the predicted value. The R_h values calculated from a 3D modeled structure of fl-LOXL2 and the crystal structure of the precursor Δ1-2SRCR-LOXL2 are within a reasonable margin of error of the values determined by SEC-MALS for fl- and Δ1-2SRCR-LOXL2s in mature forms in this study. Based on superimposition of the 3D model and the crystal structure of Δ1-2SRCR-LOXL2 (PDB:5ZE3), we propose a configuration of fl-LOXL2 that explains the difference observed in R_h between fl- and Δ1-2SRCR-LOXL2s in solution.

Deficiency of Procollagen C-Proteinase Enhancer 1 in Mice has No Major Impact on Cardiac Collagen and Function Under Basal Conditions

ABSTRACT

Maturation of fibrillar collagen is known to play a crucial role in the pathophysiology of myocardial fibrosis. Procollagen C-proteinase enhancer 1 (PCPE1) has a key role in procollagen maturation and collagen fibril formation. The phenotype of both male and female PCPE1 knock-out mice was investigated under basal conditions to explore the potential of PCPE1 as a therapeutic target in heart failure. Global constitutive PCPE1-/- mice were generated. Serum procollagen I C-terminal propeptide, organ histology, and cutaneous wound healing were assessed in both wild type (WT) and PCPE1-/- mice. In addition, the cardiac expression of genes involved in collagen metabolism was investigated and the total and insoluble cardiac collagen contents determined. Cardiac function was evaluated by echocardiography. No differences in survival, clinical chemistry, or organ histology were observed in PCPE1-/- mice compared with WT. Serum procollagen I C-terminal propeptide was lower in PCPE1-/- mice. Cardiac mRNA expression of Bmp1, Col1a1, Col3a1, and Loxl2 was similar, whereas Tgfb and Loxl1 mRNA levels were decreased in PCPE1-/- mice compared with sex-matched WT. No modification of total or insoluble cardiac collagen content was observed between the 2 strains. Ejection fraction was slightly decreased in PCPE1-/- male mice, but not in females. Finally, wound healing was not altered in PCPE1-/- mice. PCPE1 deficiency does not trigger any major liabilities and does not affect cardiac collagen content nor its function under basal conditions. Further studies are required to evaluate its role under stressed conditions and determine its suitability as a therapeutic target for heart failure.

Extraction and Purification of Extracellular L-Glutamate Oxidase from Streptomyces

The bacterial isolates Streptomyces were obtained from the soil and cultivated in a wheat bran medium, which was used to produce the L-glutamate oxidase enzyme. The extracellular enzyme was then extracted using a cooling centrifugation process to obtain the filtrate that represents the crude enzyme. Afterward, the enzyme purification processes were carried out which included precipitation with ammonium sulfate as a preliminary purification step followed by dialysis to remove the salts. Next, ion-exchange chromatography and gel filtration were used to finish the purification process, and the enzyme activity was determined for each purification step. The results of purification of L-glutamate oxidase enzyme from streptomyces using ammonium sulfate showed that the specific activity was 8.25 units/mg protein with a saturation ratio of 60%. Moreover, the results of purification using a dialysis tube indicated that the specific activity was 9.5 units/mg protein. In addition, the result of purification using diethylaminoethyl cellulose ion column revealed that the specific activity was 25 unit/mg protein and the results of purification using gel filtration showed that the specific activity was 56 units/mg protein which was the best step in the purification process due to high specific activity of the enzyme. The optimum temperature and pH for the activity and stability of the enzyme were tested. Based on the findings, the optimum temperature for the activity of the enzyme was 37 °C. In addition, it was found that the optimum temperature range for the stability of the enzyme was 30-50 °C. Besides, the optimum pH for the activity was 7.0 and the optimum pH range for the enzyme stability was 5.0-7.0.

LOXL2-enriched small extracellular vesicles mediate hypoxia-induced premetastatic niche and indicates poor outcome of head and neck cancer

Small extracellular vesicles (sEVs) operate as a signaling platform due to their ability to carry functional molecular cargos. However, the role of sEVs in hypoxic tumor microenvironment-mediated premetastatic niche formation remains poorly understood. Methods: Protein expression profile of sEVs derived from normoxic and hypoxic head and neck squamous cell carcinoma (HNSCC) cells were determined by Isobaric Tagging Technology for Relative Quantitation. In vitro invasion assay and in vivo colonization were performed to evaluate the role of sEV-delivering proteins. Results: We identified lysyl oxidase like 2 (LOXL2) which had the highest fold increase in hypoxic sEVs compared with normoxic sEVs. Hypoxic cell-derived sEVs delivered high amounts of LOXL2 to non-hypoxic HNSCC cells to elicit epithelial-to-mesenchymal transition (EMT) and induce the invasion of the recipient cancer cells. Moreover, LOXL2-enriched sEVs were incorporated by distant fibroblasts and activate FAK/Src signaling in recipient fibroblasts. Increased production of fibronectin mediated by FAK/Src signaling recruited myeloid-derived suppressor cells to form a premetastatic niche. Serum sEV LOXL2 can reflect a hypoxic and aggressive tumor type and can serve as an alternative to tissue LOXL2 as an independent prognostic factor of overall survival for patients with HNSCC. Conclusion: sEVs derived from the hypoxic tumor microenvironment of HNSCC can drive local invasion of non-hypoxic HNSCC cells and stimulate premetastatic niche formation by delivering LOXL2 to non-hypoxic HNSCC cells and fibroblasts to induce EMT and fibronectin production, respectively.

Catalytic mechanism of ancestral L-lysine oxidase assigned by sequence data mining

A large number of protein sequences are registered in public databases such as PubMed. Functionally uncharacterized enzymes are included in these databases, some of which likely have potential for industrial applications. However, assignment of the enzymes remained difficult tasks for now. In this study, we assigned a total of 28 original sequences to uncharacterized enzymes in the FAD-dependent oxidase family expressed in some species of bacteria including Chryseobacterium, Flavobacterium, and Pedobactor. Progenitor sequence of the assigned 28 sequences was generated by ancestral sequence reconstruction, and the generated sequence exhibited L-lysine oxidase activity; thus, we named the enzyme AncLLysO. Crystal structures of ligand-free and ligand-bound forms of AncLLysO were determined, indicating that the enzyme recognizes L-Lys by hydrogen bond formation with R76 and E383. The binding of L-Lys to AncLLysO induced dynamic structural change at a plug loop formed by residues 251 to 254. Biochemical assays of AncLLysO variants revealed the functional importance of these substrate recognition residues and the plug loop. R76A and E383D variants were also observed to lose their activity, and the kcat/Km value of G251P and Y253A mutations were approximately 800- to 1800-fold lower than that of AncLLysO, despite the indirect interaction of the substrates with the mutated residues. Taken together, our data demonstrate that combinational approaches to sequence classification from database and ancestral sequence reconstruction may be effective not only to find new enzymes using databases of unknown sequences but also to elucidate their functions.

LOXL2 attenuates osteoarthritis through inactivating Integrin/FAK signaling

Temporomandibular joint OA (TMJOA) is a common degenerative joint disease, leads to structural damage and ultimately loss of function. Matrix degradation is one of the first pathogenesis during the progression of OA, it was effective to inhibit matrix degradation to block the development of OA. In this study, an in vivo model (compressive mechanical force) and an in vitro model (IL-1β) were used to induce OA-like changes in TMJ cartilage and chondrocytes. We revealed lysyl oxidase like-2 (LOXL2) play a critical role in TMJOA. LOXL2 expression decreased in mechanical stress/IL-β induced TMJOA-like lesions in both in vivo models and in vitro models. Furthermore, recombinant LOXL2 (rhLOXL2) treatment ameliorated the degenerative changes induced by mechanical stress in vivo, including the thinning cartilage, down-expression of collagen II and proteoglycan, and over-expression of TNF-a, while LOXL2 antibody (anti-LOXL2) treatment exacerbated these changes. Mechanistically, the protection of LOXL2 in chondrocytes was induced partly through activation of the Integrin/FAK pathway. The inhibition of the Integrin/FAK pathway could neutralized the effects caused by rhLOXL2. Collectively, our study suggests that the LOXL2 plays a protective role in mechanical stress induced TMJOA-like changes, and the Integrin/FAK pathway may be a key downstream pathway in this process.

LOXL3 Silencing Affected Cell Adhesion and Invasion in U87MG Glioma Cells

Lysyl oxidase-like 3 (LOXL3), belonging to the lysyl oxidase family, is responsible for the crosslinking in collagen or elastin. The cellular localization of LOXL3 is in the extracellular space by reason of its canonical function. In tumors, the presence of LOXL3 has been associated with genomic stability, cell proliferation, and metastasis. In silico analysis has shown that glioblastoma was among tumors with the highest LOXL3 expression levels. LOXL3 silencing of U87MG cells by siRNA led to the spreading of the tumor cell surface, and the transcriptome analysis of these cells revealed an upregulation of genes coding for extracellular matrix, cell adhesion, and cytoskeleton components, convergent to an increase in cell adhesion and a decrease in cell invasion observed in functional assays. Significant correlations of LOXL3 expression with genes coding for tubulins were observed in the mesenchymal subtype in the TCGA RNA-seq dataset of glioblastoma (GBM). Conversely, genes involved in endocytosis and lysosome formation, along with MAPK-binding proteins related to focal adhesion turnover, were downregulated, which may corroborate the observed decrease in cell viability and increase in the rate of cell death. Invasiveness is a major determinant of the recurrence and poor outcome of GBM patients, and downregulation of LOXL3 may contribute to halting the tumor cell invasion.

An in situ activity assay for lysyl oxidases

The lysyl oxidase family of enzymes (LOXs) catalyze oxidative deamination of lysine side chains on collagen and elastin to initialize cross-linking that is essential for the formation of the extracellular matrix (ECM). Elevated expression of LOXs is highly associated with diverse disease processes. To date, the inability to detect total LOX catalytic function in situ has limited the ability to fully elucidate the role of LOXs in pathobiological mechanisms. Using LOXL2 as a representative member of the LOX family, we developed an in situ activity assay by utilizing the strong reaction between hydrazide and aldehyde to label the LOX-catalyzed allysine (-CHO) residues with biotin-hydrazide. The biotinylated ECM proteins are then labeled via biotin-streptavidin interaction and detected by fluorescence microscopy. This assay detects the total LOX activity in situ for both overexpressed and endogenous LOXs in cells and tissue samples and can be used for studies of LOXs as therapeutic targets.

Stablization of ACOs by NatB mediated N-terminal acetylation is required for ethylene homeostasis

N-terminal acetylation (NTA) is a highly abundant protein modification catalyzed by N-terminal acetyltransferases (NATs) in eukaryotes. However, the plant NATs and their biological functions have been poorly explored. Here we reveal that loss of function of CKRC3 and NBC-1, the auxiliary subunit (Naa25) and catalytic subunit (Naa20) of Arabidopsis NatB, respectively, led to defects in skotomorphogenesis and triple responses of ethylene. Proteome profiling and WB test revealed that the 1-amincyclopropane-1-carboxylate oxidase (ACO, catalyzing the last step of ethylene biosynthesis pathway) activity was significantly down-regulated in natb mutants, leading to reduced endogenous ethylene content. The defective phenotypes could be fully rescued by application of exogenous ethylene, but less by its precursor ACC. The present results reveal a previously unknown regulation mechanism at the co-translational protein level for ethylene homeostasis, in which the NatB-mediated NTA of ACOs render them an intracellular stability to maintain ethylene homeostasis for normal growth and responses.

Novel mechanism for OSM-promoted extracellular matrix remodeling in breast cancer: LOXL2 upregulation and subsequent ECM alignment

BACKGROUND

Invasive ductal carcinoma (IDC) is a serious problem for patients as it metastasizes, decreasing 5-year patient survival from > 95 to ~ 27%. The breast tumor microenvironment (TME) is often saturated with proinflammatory cytokines, such as oncostatin M (OSM), which promote epithelial-to-mesenchymal transitions (EMT) in IDC and increased metastasis. The extracellular matrix (ECM) also plays an important role in promoting invasive and metastatic potential of IDC. Specifically, the reorganization and alignment of collagen fibers in stromal ECM leads to directed tumor cell motility, which promotes metastasis. Lysyl oxidase like-2 (LOXL2) catalyzes ECM remodeling by crosslinking of collagen I in the ECM. We propose a novel mechanism whereby OSM induces LOXL2 expression, mediating stromal ECM remodeling of the breast TME.

METHODS

Bioinformatics was utilized to determine survival and gene correlation in patients. IDC cell lines were treated with OSM (also IL-6, LIF, and IL-1β) and analyzed for LOXL2 expression by qRT-PCR and immunolabelling techniques. Collagen I contraction assays, 3D invasion assays, and confocal microscopy were performed with and without LOXL2 inhibition to determine the impact of OSM-induced LOXL2 on the ECM.

RESULTS

Our studies demonstrate that IDC patients with high LOXL2 and OSM co-expression had worse rates of metastasis-free survival than those with high levels of either, individually, and LOXL2 expression is positively correlated to OSM/OSM receptor (OSMR) expression in IDC patients. Furthermore, human IDC cells treated with OSM resulted in a significant increase in LOXL2 mRNA, which led to upregulated protein expression of secreted, glycosylated, and enzymatically active LOXL2. The expression of LOXL2 in IDC cells did not affect OSM-promoted EMT, and LOXL2 was localized to the cytoplasm and/or secreted. OSM-induced LOXL2 promoted an increase in ECM collagen I fiber crosslinking, which led to significant fiber alignment between cells and increased IDC cell invasion.

CONCLUSIONS

Aligned collagen fibers in the ECM provide pathways for tumor cells to migrate more easily through the stroma to nearby vasculature and tissue. These results provide a new paradigm through which proinflammatory cytokine OSM promotes tumor progression. Understanding the nuances in IDC metastasis will lead to better potential therapeutics to combat against the possibility.

Inhibitory effects of alkaline extract from the pericarp of Citrus reticulata Blanco on collagen behavior in bleomycin-induced pulmonary fibrosis

ETHNOPHARMACOLOGICAL RELEVANCE

Peel of Citrus reticulata, a Chinese herbal drug with functions of regulating Qi and expelling phlegm, has been used for the treatment of lung related diseases in Chinese medicine for a long time. Its detailed effects on collagen in anti-idiopathic pulmonary fibrosis (IPF) is still unclear.

AIM OF THE STUDY

To explore the effects of citrus alkaline extract (CAE) on collagen synthesis, crosslinking and deposition in pulmonary fibrosis and understand the possible signal pathways involved in the activity.

MATERIALS AND METHODS

CAE was prepared from C. reticulata. Bleomycin-induced pulmonary fibrosis mouse model was applied. Pulmonary fibrosis of lung was estimated with histopathology analysis, and collagen deposition was evaluated with immunohistochemistry. Collagen crosslinking related biomarkers and enzymes were analyzed with chemical methods, immunohistochemical and western blot analyses.

RESULTS

CAE oral administration lowered hydroxyproline content, inhibited the collagen deposition including expressions of collagen I and III, and relieved bleomycin-induced pulmonary fibrosis in mice model. The productions of a collagen crosslink pyridinoline and crosslinking related enzymes including lysyl oxidase (LOX), lysyl oxidase-like protein 1 (LOXL1) in lung were suppressed by CAE treatment. Furthermore, the protein expressions of TGF-β1 and Smad3 levels in lungs were also downregulated by CAE.

CONCLUSIONS

This study demonstrated that CAE inhibited collagen synthesis, crosslinking and deposition, and ameliorated bleomycin-induced pulmonary fibrosis. Preliminary mechanism study revealed that CAE exerted its bioactivity at least via downregulation of TGF-β1/Smad3 pathway. Our findings provided a great potential in fighting IPF based on CAE.

The pathological significance of LOXL2 in pre-metastatic niche formation of HCC and its related molecular mechanism

OBJECTIVE

The mechanisms underlying the contribution of primary tumour to pre-metastatic niche formation remains largely unknown in hepatocellular carcinoma (HCC). We previously reported that the released LOXL2 from HCC cells under higher stiffness stimulation facilitated the formation of lung pre-metastatic niche. Here, we further clarified the pathological role of LOXL2 in promoting lung pre-metastatic niche formation and lung metastasis occurrence in HCC and its relevant molecular mechanism.

METHODS

Using two different animal models and an in vitro system of mechanically tuneable gel mirroring lung tissue stiffness, we explored the underlying mechanism of LOXL2 in pre-metastatic niche formation.

RESULTS

We applied tail vein injection of CM-LV-LOXL2-OEsimulating tumour-released soluble factors to induce lung pre-metastatic niche formation and found that the injected LOXL2 remarkably enhanced CD11b+/CD45+ bone marrow-derived cells (BMDCs) recruitment and fibronectin expression in lung. Subsequently, LOXL2-overexpressed xenograft HCC models validated that tumour-secreted LOXL2 significantly promoted the occurrence of pulmonary metastasis. In vitro, LOXL2 and LOXL2-caused matrix stiffening not only obviously upregulated the expressions of MMP9 and fibronectin in lung fibroblasts, but also evidently increased the number of adherent HCC cells and the expression of chemokine CXCL12. The activation of PI3K-AKT pathway mediated LOXL2-upregulated fibronectin. HCC patients in High-LOXL2 group had higher ratio of tumour recurrence than HCC patients in Low-LOXL2 group, supporting a significance of LOXL2 in HCC progression and unfavourable outcome.

CONCLUSION

Primary tumour-released LOXL2 promotes lung pre-metastatic niche formation and lung metastasis occurrence. LOXL2-caused matrix stiffening synergistically regulates lung pre-metastatic niche formation. Targeting LOXL2-induced lung pre-metastatic niche may be a novel intervention approach against HCC metastasis.

Quantitative Morphometry of Elastic Fibers in Pelvic Organ Prolapse

Pelvic organ prolapse (POP) is common among older women who have delivered children vaginally. While the pathophysiology is not fully delineated, POP can occur in part from insufficient repair of disrupted elastic matrix fibers. Quantification of structural changes to elastic fibers has not been described previously for POP. The goal of this paper is to present a validated technique for morphometric analysis of elastic fibers in vaginal tissue cultures from lysyl oxidase like-1 knock out (LOXL1 KO) mice with POP. The effect of LOXL1 KO, effect of POP, effect of culture, and effect of elastogenic treatment on the changes in elastin fiber characteristics were tested using vaginal tissues from wild type multiparous (WT), LOXL1 KO multiparous prolapsed (POP) and LOXL1 KO multiparous non-prolapsed (NP) mice. Our results show significantly higher mean aspect ratio, maximum diameter and perimeter length in POP compared to NP after 3 weeks of tissue culture. Further, treatment of POP tissues in culture with growth factors with previously documented elastogenic effects caused a significant increase in the mean area and perimeter length of elastic fibers. This technique thus appears to be useful in quantifying structural changes and can be used to assess the pathophysiology of POP and the effect of elastogenic treatments with potential for POP.

Significance of nuclear LOXL2 inhibition in fibroblasts and myofibroblasts in the fibrotic process of acute respiratory distress syndrome

Fibrotic scarring is an important prognostic factor of acute respiratory distress syndrome (ARDS). There are currently no antifibrotic drugs or other therapeutic agents for ARDS. Lysyl oxidase-like 2 (LOXL2), an amine oxidase, contributes to fibrotic scarring by facilitating collagen cross-linking. Recent clinical trials revealed that a monoclonal inhibitory antibody against LOXL2 failed to show benefit over placebo in patients with fibrotic disorders involving the lungs. These clinical results raise the possibility that targeting the extracellular enzymic activity of LOXL2 is not in itself sufficient to prevent fibrotic scarring. We investigated the role of LOXL2 in the pathogenesis of ARDS in vivo, in vitro, and in samples from patients with ARDS. After lung injury, LOXL2 was unevenly expressed in the nuclei of lung fibroblasts and myofibroblasts in the fibrotic phase. Nuclear LOXL2 expression was upregulated in lung fibroblasts after transforming growth factor-beta1 (TGF-β1)-treatment. LOXL2 silencing abrogated the TGF-β1-induced expression of a myofibrogenic-progenitor marker, the appearance of proto-myofibroblasts, and the evolution of differentiated myofibroblasts in lung fibroblasts. Nuclear upregulation of Snail was evident in myofibroblasts during the fibrotic phase after lung injury. We detected high levels of LOXL2 protein in the lungs of ARDS patients, specifically during the proliferative and fibrotic phases. Our results highlight nuclear LOXL2 in fibroblasts as a primary causative driver of cell-fate decision toward myofibroblasts and of the progression of fibrotic scarring. A nuclear-LOXL2-targeted agent could be a promising therapeutic strategy against fibrotic disorders including ARDS.

BES1 negatively regulates the expression of ACC oxidase 2 to control the endogenous level of ethylene in Arabidopsis thaliana

Quantitative reverse transcription PCR (qRT-PCR) analysis and ProACO2::GUS expression showed that ACO2 was highly expressed in the shoots of Arabidopsis seedlings under light conditions. Exogenously applied aminocyclopropane-1-carboxylic acid (ACC) enhanced the expression of ACO2, whereas Co²⁺ ions suppressed its expression. In comparison with wild-type seedlings, the ACO2 knockdown mutant aco2-1 produced less ethylene, which resulted in the inhibited growth of Arabidopsis seedlings. Exogenously applied brassinolide reduced the expression of ACO2. ACO2 expression was increased in det2, a brassinosteroid (BR)-deficient mutant; however, it was decreased in bes1-D, a brassinosteroid insensitive 1-EMS-suppressor 1 (BES1)-dominant mutant. In the putative promoter region of ACO2, 11 E-box sequences for BES1 binding but not BR regulatory element sequences for brassinazole-resistant 1 (BZR1) binding were found. Chromatin immunoprecipitation assay showed that BES1 could directly bind to the E-boxes located in the putative promoter region of ACO4. Less ethylene was produced in bes1-D seedlings compared with wild-type seedlings, suggesting that the direct binding of BES1 to the ACO2 promoter may negatively regulate ACO2 expression to control the endogenous level of ethylene in Arabidopsis seedlings.

Highly selective synthesis of D-amino acids via stereoinversion of corresponding counterpart by an in vivo cascade cell factory

BACKGROUND

D-Amino acids are increasingly used as building blocks to produce pharmaceuticals and fine chemicals. However, establishing a universal biocatalyst for the general synthesis of D-amino acids from cheap and readily available precursors with few by-products is challenging. In this study, we developed an efficient in vivo biocatalysis system for the synthesis of D-amino acids from L-amino acids by the co-expression of membrane-associated L-amino acid deaminase obtained from Proteus mirabilis (LAAD), meso-diaminopimelate dehydrogenases obtained from Symbiobacterium thermophilum (DAPDH), and formate dehydrogenase obtained from Burkholderia stabilis (FDH), in recombinant Escherichia coli.

RESULTS

To generate the in vivo cascade system, three strategies were evaluated to regulate enzyme expression levels, including single-plasmid co-expression, double-plasmid co-expression, and double-plasmid MBP-fused co-expression. The double-plasmid MBP-fused co-expression strain Escherichia coli pET-21b-MBP-laad/pET-28a-dapdh-fdh, exhibiting high catalytic efficiency, was selected. Under optimal conditions, 75 mg/mL of E. coli pET-21b-MBP-laad/pET-28a-dapdh-fdh whole-cell biocatalyst asymmetrically catalyzed the stereoinversion of 150 mM L-Phe to D-Phe, with quantitative yields of over 99% ee in 24 h, by the addition of 15 mM NADP+ and 300 mM ammonium formate. In addition, the whole-cell biocatalyst was used to successfully stereoinvert a variety of aromatic and aliphatic L-amino acids to their corresponding D-amino acids.

CONCLUSIONS

The newly constructed in vivo cascade biocatalysis system was effective for the highly selective synthesis of D-amino acids via stereoinversion.

The regulation of ethylene biosynthesis: a complex multilevel control circuitry

The gaseous plant hormone ethylene is produced by a fairly simple two-step biosynthesis route. Despite this pathway's simplicity, recent molecular and genetic studies have revealed that the regulation of ethylene biosynthesis is far more complex and occurs at different layers. Ethylene production is intimately linked with the homeostasis of its general precursor S-adenosyl-l-methionine (SAM), which experiences transcriptional and posttranslational control of its synthesising enzymes (SAM synthetase), as well as the metabolic flux through the adjacent Yang cycle. Ethylene biosynthesis continues from SAM by two dedicated enzymes: 1-aminocyclopropane-1-carboxylic (ACC) synthase (ACS) and ACC oxidase (ACO). Although the transcriptional dynamics of ACS and ACO have been well documented, the first transcription factors that control ACS and ACO expression have only recently been discovered. Both ACS and ACO display a type-specific posttranslational regulation that controls protein stability and activity. The nonproteinogenic amino acid ACC also shows a tight level of control through conjugation and translocation. Different players in ACC conjugation and transport have been identified over the years, however their molecular regulation and biological significance is unclear, yet relevant, as ACC can also signal independently of ethylene. In this review, we bring together historical reports and the latest findings on the complex regulation of the ethylene biosynthesis pathway in plants.

Structural basis for stereospecificity to d-amino acid of glycine oxidase from Bacillus cereus ATCC 14579

Glycine oxidase (GO) is an enzyme that catalyzes the oxidation of the primary and secondary amines of various chemicals, including glycine, and the enzyme has been applied in a variety of fields, such as biosensor and genetically modified glyphosate resistance plants. Here, we report that the gene product of BC0747 from Bacillus cereus (BcGO) shows oxidase activity for glycine and small d-amino acids, such as d-proline and d-alanine. We also determined the crystal structure of BcGO complexed with the FAD cofactor at a 2.36 Å resolution and revealed how the cofactor binds to the deep pocket of the enzyme. We performed the molecular docking calculation of the glycine substrate to the BcGO structure and identified how the carboxyl- and amine-groups of the d-amino acid are stabilized at the substrate binding site. Structural analysis of BcGO also provided information on the structural basis for the stereospecificity of the enzyme to d-amino acids. In addition, we placed the glyphosate molecule, a plant herbicide, at the substrate binding site, and explained how the mutation of Gly51 to arginine enhances enzyme activity.

Functional Validation of Glutamine synthetase and Glutamate synthase Genes in Durum Wheat near Isogenic Lines with QTL for High GPC

Durum wheat (Triticum turgidum L. ssp. durum) is a minor crop grown on about 17 million hectares of land worldwide. Several grain characteristics determine semolina's high end-use quality, such as grain protein content (GPC) which is directly related to the final products' nutritional and technological values. GPC improvement could be pursued by considering a candidate gene approach. The glutamine synthetase (GS)/glutamate synthase (GOGAT) cycle represents a bottleneck in the first step of nitrogen assimilation. QTL for GPC have been located on all chromosomes, and several major ones have been reported on 2A and 2B chromosomes, where GS2 and Fd-GOGAT genes have been mapped. A useful and efficient method to validate a putative QTL is the constitution of near-isogenic lines (NILs) by using the marker found to be associated to that QTL. Here, we present the development of two distinct sets of heterogeneous inbred family (HIF)- based NILs segregating for GS2 and Fd-GOGAT genes obtained from heterozygous lines at those loci, as well as their genotypic and phenotypic characterizations. The results allow the validation of the previously identified GPC QTL on 2A and 2B chromosomes, along with the role of these key genes in GPC control.

LOXL2 in cancer: regulation, downstream effectors and novel roles

Lysyl oxidase-like 2 (LOXL2) is a copper and lysine tyrosyl-quinone (LTQ)-dependent amine oxidase belonging to the lysyl oxidase (LOX) family, the canonical function of which is to catalyze the crosslinking of elastin and collagen in the extracellular matrix (ECM). Many studies have revealed that the aberrant expression of LOXL2 in multiple cancers is associated with epithelial-mesenchymal transition (EMT), metastasis, poor prognosis, chemoradiotherapy resistance, and tumor progression. LOXL2 is regulated in many ways, such as transcriptional regulation, alternative splicing, microRNA regulation, posttranslational modification, and cleavage. Beyond affecting the extracellular environment, various intracellular roles, such as oxidation and deacetylation activities in the nucleus, have been reported for LOXL2. Additionally, LOXL2 contributes to tumor cell invasion by promoting cytoskeletal reorganization. Targeting LOXL2 has become a potential therapeutic strategy to combat many types of cancers. Here, we provide an overview of the regulation and downstream effectors of LOXL2 and discuss the intracellular role of LOXL2 in cancer.

Tracing Metabolic Fate of Mitochondrial Glycine Cleavage System Derived Formate In Vitro and In Vivo

Folate-mediated one-carbon (1C) metabolism is a major target of many therapies in human diseases. Studies have focused on the metabolism of serine 3-carbon as it serves as a major source for 1C units. The serine 3-carbon enters the mitochondria transferred by folate cofactors and eventually converted to formate and serves as a major building block for cytosolic 1C metabolism. Abnormal glycine metabolism has been reported in many human pathological conditions. The mitochondrial glycine cleavage system (GCS) catalyzes glycine degradation to CO₂ and ammonium, while tetrahydrofolate (THF) is converted into 5,10-methylene-THF. GCS accounts for a substantial proportion of whole-body glycine flux in humans, yet the particular metabolic route of glycine 2-carbon recycled from GCS during mitochondria glycine decarboxylation in hepatic or bone marrow 1C metabolism is not fully investigated, due to the limited accessibility of human tissues. Labeled glycine at 2-carbon was given to humans and primary cells in previous studies for investigating its incorporations into purines, its interconversion with serine, or the CO₂ production in the mitochondria. Less is known on the metabolic fate of the glycine 2-carbon recycled from the GCS; hence, a model system tracing its metabolic fate would help in this regard. We took the direct approach of isotopic labeling to further explore the in vitro and in vivo metabolic fate of the 2-carbon from [2-¹³C]glycine and [2-¹³C]serine. As the 2-carbon of glycine and serine is decarboxylated and catabolized via the GCS, the original 13C-labeled 2-carbon is transferred to THF and yield methyleneTHF in the mitochondria. In human hepatoma cell-lines, 2-carbon from glycine was found to be incorporated into deoxythymidine (dTMP, dT + 1), M + 3 species of purines (deoxyadenine, dA and deoxyguanine, dG), and methionine (Met + 1). In healthy mice, incorporation of GCS-derived formate from glycine 2-carbon was found in serine (Ser + 2 via cytosolic serine hydroxy methyl transferase), methionine, dTMP, and methylcytosine (mC + 1) in bone marrow DNA. In these experiments, labeled glycine 2-carbon directly incorporates into Ser + 1, A + 2, and G + 2 (at C2 and C8 of purine) in the cytosol. It is noteworthy that since the serine 3-carbon is unlabeled in these experiments, the isotopic enrichments in dT + 1, Ser + 2, dA + 3, dG + 3, and Met + 1 solely come from the 2-carbon of glycine/serine recycled from GCS, re-enters the cytosolic 1C metabolism as formate, and then being used for cytosolic syntheses of serine, dTMP, purine (M + 3) and methionine. Taken together, we established model systems and successfully traced the metabolic fate of mitochondrial GCS-derived formate from glycine 2-carbon in vitro and in vivo. Nutritional supply significantly alters formate generation from GCS. More GCS-derived formate was used in hepatic serine and methionine syntheses, whereas more GCS-derived formate was used in dTMP synthesis in the bone marrow, indicating that the utilization and partitioning of GCS-derived 1C unit are tissue-specific. These approaches enable better understanding concerning the utilization of 1C moiety generated from mitochondrial GCS that can help to further elucidate the role of GCS in human disease development and progression in future applications. More studies on GCS using these approaches are underway.

Strigolactone elevates ethylene biosynthesis in etiolated Arabidopsis seedlings

The gaseous phytohormone ethylene influences many aspects of plant life, including germination, fruit ripening, senescence, and stress responses. These diverse roles of ethylene occur in part through crosstalk with other phytohormones, which affects ethylene biosynthesis and signaling pathways. We have recently shown that the phytohormones, including gibberellic acid, abscisic acid, auxin, methyl jasmonate, and salicylic acid, regulate the stability of ACC synthases (ACSs), the rate-limiting enzymes in ethylene biosynthesis. Here, we report that treatment of etiolated Arabidopsis seedlings with strigolactone (SL) increases ethylene biosynthesis. SL does not influence ACS stability or ACS gene expression, but it increases the transcript levels of a subset of ACC oxidase (ACO) genes, thereby enhancing ethylene biosynthesis. Taken together with the results of our previous study, these findings demonstrate that most phytohormones differentially regulate ethylene biosynthesis in dark-grown Arabidopsis seedlings by affecting ACS stability and/or the transcript levels of ethylene biosynthesis genes.

Wnt signaling and Loxl2 promote aggressive osteosarcoma

Osteosarcoma (OS) is the most frequent primary malignant bone tumor in urgent need of better therapies. Using genetically modified mouse models (GEMMs), we demonstrate that Wnt signaling promotes c-Fos-induced OS formation via the actions of the collagen-modifying enzyme Loxl2. c-Fos/AP-1 directly regulates the expression of the Wnt ligands Wnt7b and Wnt9a in OS cells through promoter binding, and Wnt7b and Wnt9a in turn promote Loxl2 expression in murine and human OS cells through the transcription factors Zeb1 and Zeb2. Concordantly, inhibition of Wnt ligand secretion by inactivating the Wnt-less (Wls) gene in osteoblasts in c-Fos GEMMs either early or in a therapeutic setting reduces Loxl2 expression and progression of OS. Wls-deficient osteosarcomas proliferate less, are less mineralized and are enriched in fibroblastic cells surrounded by collagen fibers. Importantly, Loxl2 inhibition using either the pan-Lox inhibitor BAPN or a specific inducible shRNA reduces OS cell proliferation in vitro and decreases tumor growth and lung colonization in murine and human orthotopic OS transplantation models. Finally, OS development is delayed in c-Fos GEMMs treated with BAPN or with specific Loxl2 blocking antibodies. Congruently, a strong correlation between c-FOS, LOXL2 and WNT7B/WNT9A expression is observed in human OS samples, and c-FOS/LOXL2 co-expression correlates with OS aggressiveness and decreased patient survival. Therefore, therapeutic targeting of Wnt and/or Loxl2 should be considered to potentiate the inadequate current treatments for pediatric, recurrent, and metastatic OS.

Reaction mechanism of lysyl oxidase-like 2 (LOXL2) studied by computational methods

Lysyl oxidase-like 2 (LOXL2) is a copper-dependent amine oxidase that catalyzes the oxidative deamination of the ε-amino group of lysines/hydroxylysines on substrate proteins (collagen and elastin) to form aldehyde groups. The generated aldehyde groups are of significance in crosslinking with the adjacent aldehyde or ε-amino group on proteins in extracellular matrix. In this paper, we have studied the reaction mechanism of LOXL2 by means of quantum mechanics (QM) and combined QM and molecular mechanics (QM/MM) methods. This study is divided into two parts, i.e. the biosynthesis of lysine tyrosylquinone (LTQ) cofactor and oxidative deamination of ε-amino group of lysine by LTQ. For the former part, the reaction is driven by a large exothermicity of about 284 kJ/mol. Dopaquinone radical (DPQr) is suggested to be an intermediate state in this reaction. In addition, His652 residue is predicted to serve as proton acceptor. The rate-determining step for the biosynthesis of LTQ is found to be hydrogen-atom abstraction from the benzene ring on substrate by Cu²⁺-hydroxide, which is a proton-coupled electron transfer (PCET) process with an energy barrier of 84 kJ/mol. For the latter part, the reaction is exothermic by about 145 kJ/mol, and the copper ion is proposed to play a role of redox catalyst in the last step to generate the product of aldehyde. However, the copper ion might not be indispensable for the latter part, which is consistent with the previous study.