Collagen beta (1-O) galactosyltransferase 1 (GLT25D1) is required for the secretion of high molecular weight adiponectin and affects lipid accumulation

Upregulation of GLT25D1 in Hepatic Stellate Cells Promotes Liver Fibrosis via the TGF-β1/SMAD3 Pathway In Vivo and In vitro

BACKGROUND AND AIMS

Collagen β(1-O) galactosyltransferase 25 domain 1 (GLT25D1) is associated with collagen production and glycosylation, and its knockout in mice results in embryonic death. However, its role in liver fibrosis remains elusive, particularly in hepatic stellate cells (HSCs), the primary collagen-producing cells associated with liver fibrogenesis. Herein, we aimed to elucidate the role of GLT25D1 in HSCs.

METHODS

Bile duct ligation (BDL)-induced mouse liver fibrosis models, primary mouse HSCs (mHSCs), and transforming growth factor beta 1 (TGF-β1)-stimulated LX-2 human hepatic stellate cells were used in in vivo and in vitro studies. Stable LX-2 cell lines with either GLT25D1 overexpression or knockdown were established using lentiviral transfection. RNA-seq was performed to investigate the genomic differences. HPLC-MS/MS were used to identify glycosylation sites. Scanning electronic microscopy (SEM) and second-harmonic generation/two-photon excited fluorescence (SHG/TPEF) were used to image collagen fibril morphology.

RESULTS

GLT25D1 expression was upregulated in nonparenchymal cells in human cirrhotic liver tissues. Meanwhile, its knockdown attenuated collagen deposition in BDL-induced mouse liver fibrosis and inhibited mHSC activation. GLT25D1 was overexpressed in activated versus quiescence LX-2 cells and regulated in vitro LX-2 cell activation, including proliferation, contraction, and migration. GLT25D1 also significantly increased liver fibrogenic gene and protein expression. GLT25D1 upregulation promoted HSC activation and enhanced collagen expression through the TGF-β1/SMAD signaling pathway. Mass spectrometry showed that GLT25D1 regulated the glycosylation of collagen in HSCs, affecting the diameter of collagen fibers.

CONCLUSIONS

Collectively, the upregulation of GLT25D1 in HSCs promoted the progression of liver fibrosis by affecting HSCs activation and collagen stability.

20 Years with SGBS cells - a versatile in vitro model of human adipocyte biology

20 years ago, we described a human cell strain derived from subcutaneous adipose tissue of an infant supposed to have Simpson-Golabi-Behmel Syndrome (SGBS), thus called “SGBS cells”. Since then, these cells have emerged as the most commonly used cell model for human adipogenesis and human adipocyte biology. Although these adipocyte derived stem cells have not been genetically manipulated for transformation or immortalization, SGBS cells retain their capacity to proliferate and to differentiate into adipocytes for more than 50 population doublings, providing an almost unlimited source of human adipocyte progenitor cells. Original data obtained with SGBS cells led to more than 200 peer reviewed publications comprising investigations on adipogenesis and browning, insulin sensitivity, inflammatory response, adipokine production, as well as co-culture models and cell-cell communication. In this article, we provide an update on the characterization of SGBS cells, present basic methods for their application and summarize results of a systematic literature search on original data obtained with this cell strain.

Collagen β(1-O) galactosyltransferase 2 deficiency contributes to lipodystrophy and aggravates NAFLD related to HMW adiponectin in mice

AIM

Our previous results showed that Colgalt1 knock-out resulted in fetal death on day E11.5, and collagen secretion was retarded. This study aimed to elucidate the role of Collagen β(1-O) galactosyltransferase 2 (Colgalt2) in the pathogenesis of non-alcoholic fatty liver disease (NAFLD).

METHODS

Colgalt2^-/- mice were fed a high-fat diet (HFD) or methionine-and choline-deficient diet (MCD). Nanopore long-read RNA-Seq analysis of liver tissues was used to profile genomic variation. In vitro, hepatocyte steatosis and differentiation of primary pre-adipocytes were induced.

RESULTS

Colgalt2^-/- mice exhibited lipodystrophy, increased body weight, and hepatic lipid accumulation at 6 weeks of age. Colgalt2 deficiency aggravated hepatic steatosis in mice fed an HFD or a standard laboratory chow diet. Colgalt2 deficiency promotes steatohepatitis in MCD-fed mice. In HFD mice, Colgalt2 deficiency caused lipodystrophy and decreased plasma HMW, total adiponectin, and leptin levels. Colgalt2 deficiency also reduced circulating HMW/Total adiponectin in mice fed a HFD diet without differences of adiponectin mRNA and protein level in WT and Colgalt2^-/- mice. The nanopore long-read RNA-Seq analysis results revealed transcriptional changes in the adiponectin receptor downstream signaling pathway and lipogenic genes, including the AMPK signaling pathway, adipocytokine signaling pathway, and lipid metabolism (Cidea, Cidec, CD36, and PPARγ). Colgalt2 deficiency did not promote lipid accumulation in OA-induced HepG2 cells or primary hepatocytes. However, Colgalt2 deficiency inhibited adipogenesis and reduced PPARγ, adipogenesis-related transcription factors, and expression during adipocyte differentiation.

CONCLUSIONS

In mice, Colgalt2 deficiency contributes to lipodystrophy and promotes NAFLD related to HMW adiponectin. These results suggest that Colgalt2 could be a novel and promising therapeutic strategy for the treatment of NAFLD.

Potential prognostic markers and significant lncRNA-mRNA co-expression pairs in laryngeal squamous cell carcinoma

lncRNA-mRNA co-expression pairs and prognostic markers related to the development of laryngeal squamous cell carcinoma (LSCC) were investigated. The lncRNA and mRNA expression data of LSCC in GSE84957 and RNA-seq data of 112 LSCC samples from TCGA database were used. Differentially expressed genes (DEGs) and lncRNAs (DE-lncRNAs) between LSCC and para-cancer tissues were identified. Co-expression analysis of DEGs and DE-lncRNA was conducted. Protein-protein interaction network for co-expressed DEGs of top 25 DE-lncRNA was constructed, followed by survival analysis for key nodes in co-expression network. Finally, expressions of several DE-lncRNAs and DEGs were verified using qRT-PCR. The lncRNA-mRNA network showed that ANKRD20A5P, C21orf15, CYP4F35P, LOC_I2_011146, XLOC_006053, XLOC_I2_003881, and LOC100506027 were highlighted in network. Some DEGs, including FUT7, PADI1, PPL, ARHGAP40, MUC21, and CEACAM1, were co-expressed with above lncRNAs. Survival analysis showed that PLOD1, GLT25D1, and KIF22 were significantly associated with prognosis. qRT-PCR results showed that the expressions of MUC21, CEACAM1, FUT7, PADI1, PPL, ARHGAP40, ANKRD20A5P, C21orf15, CYP4F35P, XLOC_I2_003881, LOC_I2_011146, and XLOC_006053 were downregulated, whereas the expression of LOC100506027 was upregulated in LSCC tissues. PLOD1, GLT25D1, and KIF22 may be potential prognostic markers in the development of LSCC. C21orf15-MUC21/CEACAM1/FUT7/PADI1/PPL/ARHGAP40 are potential lncRNA-mRNA pairs that play significant roles in the development of LSCC.

Genetic and Epigenetic Interplay Within a COLGALT2 Enhancer Associated With Osteoarthritis

OBJECTIVE

The osteoarthritis (OA)-associated single-nucleotide polymorphism (SNP) rs11583641 is located in COLGALT2, encoding a posttranslational modifier of collagen. In cartilage, the SNP genotype correlates with DNA methylation in a putative enhancer. This study was undertaken to characterize the mechanistic relationship between rs11583641, the putative enhancer, and COLGALT2 expression using cartilage samples from human patients and a chondrocyte cell model.

METHODS

Nucleic acids were extracted from articular cartilage samples obtained from patients with OA (n = 137). Samples were genotyped, and DNA methylation was quantified at 12 CpGs using pyrosequencing. The putative enhancer was deleted in Tc28a2 chondrocytes using clustered regularly interspaced short palindromic repeat/Cas9, and the impact on nearby gene expression was determined using real-time quantitative polymerase chain reaction. Targeted modulation of the epigenome using catalytically dead Cas9 (dCas9) constructs fused to DNA methyltransferase 3a or ten-eleven translocase 1 allowed for the investigation of a causal relationship between DNA methylation and enhancer activity.

RESULTS

The genotype at rs11583641 correlated with DNA methylation at 3 CpGs, and the presence of the OA risk allele, C, corresponded to reduced levels of methylation. Deletion of the enhancer resulted in a 2.7-fold reduction in COLGALT2 expression. Targeted methylation and demethylation of the CpGs had antagonistic effects on COLGALT2 expression. An allelic imbalance in the expression of COLGALT2 was identified in the cartilage from patients with OA, with relative overexpression of the OA risk allele. Allelic expression ratios correlated with DNA methylation at 4 CpGs.

CONCLUSION

COLGALT2 is a target of OA genetic risk at this locus. The genotype at rs11583641 impacts DNA methylation in a gene enhancer, which, in turn, modulates COLGALT2 expression. COLGALT2 encodes an enzyme that initiates posttranslational glycosylation of collagens and is therefore a compelling OA susceptibility target.

Collagen hydroxylysine glycosylation: non-conventional substrates for atypical glycosyltransferase enzymes

Collagen is a major constituent of the extracellular matrix (ECM) that confers fundamental mechanical properties to tissues. To allow proper folding in triple-helices and organization in quaternary super-structures, collagen molecules require essential post-translational modifications (PTMs), including hydroxylation of proline and lysine residues, and subsequent attachment of glycan moieties (galactose and glucose) to specific hydroxylysine residues on procollagen alpha chains. The resulting galactosyl-hydroxylysine (Gal-Hyl) and less abundant glucosyl-galactosyl-hydroxylysine (Glc-Gal-Hyl) are amongst the simplest glycosylation patterns found in nature and are essential for collagen and ECM homeostasis. These collagen PTMs depend on the activity of specialized glycosyltransferase enzymes. Although their biochemical reactions have been widely studied, several key biological questions about the possible functions of these essential PTMs are still missing. In addition, the lack of three-dimensional structures of collagen glycosyltransferase enzymes hinders our understanding of the catalytic mechanisms producing this modification, as well as the impact of genetic mutations causing severe connective tissue pathologies. In this mini-review, we summarize the current knowledge on the biochemical features of the enzymes involved in the production of collagen glycosylations and the current state-of-the-art methods for the identification and characterization of this important PTM.

Exosomes Secreted by Adipose-Derived Mesenchymal Stem Cells Foster Metastasis and Osteosarcoma Proliferation by Increasing COLGALT2 Expression

Objectives

Homosapien collagen beta (1-O) galactosyl transferase 2 (COLGALT2) is an important enzyme during collagen glycosylation, yet its biological functions in cancer are incompletely understood. Our previous study revealed that in the osteosarcoma microenvironment, adipose-derived mesenchymal stem cells (ADSCs) demonstrate cancer-promoting effects, but the exact mechanisms remain unclear. The aim of this study was to investigate the role of COLGALT2 in the osteosarcoma-fostering effects of ADSCs.

Materials and Methods

In this study, we compared COLGALT2 expression between primary and metastatic osteosarcoma tissues and found that metastatic tissues expressed significantly higher COLGALT2 levels. Then, we isolated and identified exosomes secreted by ADSCs. Additionally, we assessed the roles of ADSC exosomes and COLGALT2 in the osteosarcoma-promoting effects of ADSCs.

Results

Our results showed that ADSC exosomes could foster the invasion, migration, and proliferation of osteosarcoma cells, together with increasing COLGALT2 expression. COLGALT2 inhibition in MG63 cells suppressed the ADSC exosome-mediated fostering of osteosarcoma cell invasion, migration and proliferation in vitro. Conversely, COLGALT2 overexpression promoted U-2OS cell invasion, migration and proliferation in vitro. Additionally, COLGALT2 inhibition attenuated metastasis and tumor growth, and ADSC exosomes promoted tumor progression, as demonstrated in a nude mouse model of osteosarcoma.

Conclusion

According to these data, ADSC exosomes foster osteosarcoma progression by increasing COLGALT2 expression in osteosarcoma cells.

Down-regulation of GLT25D1 inhibited collagen secretion and involved in liver fibrogenesis

Collagen β (1-O) galactosyltransferase 1 (GLT25D1) has been reported to transfer galactose to hydroxylysine residues via β (1-O) linkages in collagen. However, the role of Glt25d1 in liver fibrogenesis is still unknow. Recently, we generated a Glt25d1 knockout mouse to elucidate the role of Glt25d1 in vivo. However, we found that complete deletion of the Glt25d1 gene resulted in embryonic lethality at E11.5. Histopathological analysis revealed that dysplasia in Glt25d1^-/- labyrinth with defects of the vascular network. Immunohistochemical showed that the decrease in proliferation of Glt25d1^-/- liver and the developing central nervous system (CNS). The role of Glt25d1 in liver fibrogenesis was explored by Glt25d1^+/- mice. Glt25d1^+/- mice and wild-type (WT) mice were injected intraperitoneally with the same dose of CCl₄. The higher level of serum alanine aminotransferase was observed in Glt25d1^+/- mice. Reverse transcription-quantitative polymerase chainreaction demonstrated that the mRNA expression levels of the inflammatory cytokines such as, Tnf-α, Cxcl-1 and Mcp-1, showed a significantly increase in CCl₄-treated Glt25d1^+/- mice. Collagen-I, collagen-III and α-SMA transcripts accumulation was markedly increased in the Glt25d1^+/- mice. However, Masson's trichrome staining revealed a trend to decrease in the ECM proteins deposition of Glt25d1^+/- liver. Immunohistochemistry and Western blots revealed that the protein expression of Collagen-III was reduced and a trend to a decrease in collagen-I was observed in the Glt25d1^+/- liver compared with those of WT mice. Our results demonstrate that Glt25d1 knockout results in embryonic lethality and down-regulation of Glt25d1 may inhibit collagen secretion during liver fibrogenesis.

Identification and characterization of collagen-like glycosylation and hydroxylation of CCN1

CCN1 is a secreted protein and belongs to the CCN family of matricellular proteins. CCN1 binds to various cell surface receptors; thus, CCN1 has important functions in cell proliferation, migration and angiogenesis through a variety of signaling pathways. We have reported that CCN1 is O-fucosylated and that this O-fucosylation regulates the secretion of CCN1 into the extracellular region. In this study, we detected collagen-like glycosylation and hydroxylation at Lys203 of recombinant CCN1 by mass spectrometry. We then examined the role of collagen-like glycosylation in the functions of CCN1. As a result, we found that a deficiency in collagen-like glycosylation decreased the secretion of CCN1 using wild-type CCN1- and collagen-like glycosylation-defective mutant CCN1-overexpressing cell lines. Further, knockout of lysyl hydroxylase3, a multifunctional protein with hydroxylase and glucosyltransferase activities, impaired the secretion and glycosylation level of recombinant CCN1. Previous studies reported that collagen glycosylation of Lys residues mediated by lysyl hydroxylase3 is glucosyl-galactosyl-hydroxylation, presuming that this collagen-like glycosylation detected at Lys203 of recombinant CCN1 in this study might be glucosyl-galactosyl-hydroxylation. Taken together, our results demonstrate the novel function of the collagen-like glycosylation of CCN1 and suggest that lysyl hydroxylase3-mediated glycosylation is important for CCN1 secretion.

Comparative evaluation of periodontal ligament fibroblasts stored in different types of milk: effects on viability and biosynthesis of collagen

Milk remains one of the most frequently recommended solutions for storage of avulsed teeth because it can maintain cell viability and is easily accessible. However, some negative effects of milk on avulsed teeth have been reported, just as the effects of milk on the long-term functions of cells are not clear. This study aimed to evaluate the effects of different types of milk on the viability, proliferation, and functions of periodontal ligament fibroblasts (PDLF)s in vitro. Human PDLFs were culture-medium depleted for 5 min and stored in Hanks' balanced salt solution (HBSS), whole cow's milk, low-fat cow's milk, or almond milk for 1 h at 25°C. Cell viability and proliferation were assessed using MTT assays. Expression of the genes encoding type I collagen and its modifying enzymes were analyzed using real-time PCR. Collagen matrix production was evaluated using Picrosirius red polarization. Our results showed the overall efficiency of low-fat cow's milk in maintaining the viability and proliferation of PDLFs, and in enhancing the process of collagen production. Almond milk storage resulted in the highest rate of PDLF proliferation, and comparable collagen biosynthesis ability to the control. Therefore, besides low-fat cow's milk, almond milk may potentially be an alternative tooth-storage medium for PDLF preservation and PDL tissue regeneration.

Collagen glycosylation

Despite the ubiquity of collagens in the animal kingdom, little is known about the biology of the disaccharide Glc(α1-2)Gal(β1-O) bound to hydroxylysine across collagens from sponges to mammals. The extent of collagen glycosylation varies by the types of collagen, with basement membrane collagen type IV being more glycosylated than fibrillar collagens. Beyond true collagens, proteins including collagen domains such as the complement protein 1Q and the hormone adiponectin also feature glycosylated hydroxylysine. Collagen glycosylation is initiated in the endoplasmic reticulum by the galactosyltransferases COLGALT1 and COLGALT2. Mutations in the COLGALT1 gene cause cerebral small vessel abnormality and porencephaly, which are common in collagen type IV deficiency. Beyond the strongly conserved Glc(α1-2)Gal(β1-O) glycan, additional forms of collagen glycosylation have been described in the deep-sea worm Riftia pachyptila and in the giant virus Mimivirus, thereby suggesting that further forms of collagen glycosylation are likely to be identified in the future.

Downregulation of Glt25d1 aggravates carbon tetrachloride‑induced acute hepatic injury through activation of the TGF‑β1/Smad2 signaling pathway

Collagen β (1-O) galactosyltransferase 1 (GLT25D1) has been reported to transfer galactose to hydroxylysine residues via β (1-O) linkages in collagen. The present study investigated the function of the collagen galactosyltransferase activity of GLT25D1 against carbon tetrachloride (CCl₄)-induced acute liver injury in vitro. Glt25d1^+/− mice and wild-type (WT) mice were injected intraperitoneally with the same dose of CCl₄. The grade of hepatic injury and the extent of hepatocyte necrosis in the acute phase were assessed 48 h following CCl₄ injection. Hepatocyte necrosis was evaluated by histological examination and by serum alanine aminotransferase and aspartate aminotransferase levels, which were higher in the Glt25d1^+/− mice compared with those in the WT mice. Reverse transcription-quantitative polymerase chain reaction was performed, and the results demonstrated that the mRNA expression levels of inflammatory cytokines, including tumor necrosis factor-α and interleukin-6 were significantly increased in the Glt25d1^+/− mice. Furthermore, western blot analyses were performed, and the results demonstrated that the protein levels of cleaved caspase-3 and −9 were also markedly increased in the Glt25d1^+/− liver, indicating that hepatocyte apoptosis was induced. Additionally, the expression levels of transforming growth factor (TGF)-β1 and phosphorylated small mothers against decapentaplegic (Smad)2 were markedly upregulated, indicating activation of the TGF-β1/Smad2 signaling pathway during CCl₄-induced acute liver injury in Glt25d1^+/− mice. CCl₄ administration also resulted in severe damage to Glt25d1^+/− primary hepatocytes in vitro. Taken together, the downregulation of Glt25d1 deteriorated CCl₄-induced liver injury in mice, which may involve triggering inflammatory responses, apoptosis and TGF-β1/Smad2 signaling pathway activation.

Adiponectin and Its Isoforms in Pathophysiology

Adiponectin circulates in blood in multiple isoforms. High molecular weight (HMW) adiponectin is thought to be most biologically active and promotes glucose uptake, insulin sensitivity, and fatty acid oxidation. In obesity, adiponectin isoform formation is disrupted, leading to an inverse association between metabolic disease and HMW and total adiponectin. Adiponectin isoforms also function as acute-phase reactants influencing inflammation in acute and chronic disease. Interestingly, adiponectin and mortality have a U-shaped association. Unfortunately, data concerning adiponectin and its pathophysiologic function conflict. This is predominantly due to difficulties in adequate measurement of adiponectin isoforms and lack of a gold standard. In this review we provide a general overview of the formation and function of adiponectin and its isoforms under physiologic conditions. We highlight the ways adiponectin isoform formation is disrupted in obesity and its ensuing pathologic conditions. Furthermore, we will elaborate on the role of adiponectin isoforms as inflammatory proteins with respect to cardiac and kidney disease and discuss the association of adiponectin with mortality. Finally, we will provide a historical perspective on the measurement of adiponectin isoforms, current limitations, and future challenges.