Serglycin in Health and Diseases

Serglycin secreted by late-stage nucleus pulposus cells is a biomarker of intervertebral disc degeneration

Intervertebral disc degeneration is a natural process during aging and a leading cause of lower back pain. Here, we generate a comprehensive atlas of nucleus pulposus cells using single-cell RNA-seq analysis of human nucleus pulposus tissues (three males and four females, age 41.14 ± 18.01 years). We identify fibrotic late-stage nucleus pulposus cells characterized by upregulation of serglycin expression which facilitate the local inflammatory response by promoting the infiltration of inflammatory cytokines and macrophages. Finally, we discover that daphnetin, a potential serglycin ligand, substantially mitigates the local inflammatory response by downregulating serglycin expression in an in vivo mouse model, thus alleviating intervertebral disc degeneration. Taken together, we identify late-stage nucleus pulposus cells and confirm the potential mechanism by which serglycin regulates intervertebral disc degeneration. Our findings indicate that serglycin is a latent biomarker of intervertebral disc degeneration and may contribute to development of diagnostic and therapeutic strategies.

HS, an Ancient Molecular Recognition and Information Storage Glycosaminoglycan, Equips HS-Proteoglycans with Diverse Matrix and Cell-Interactive Properties Operative in Tissue Development and Tissue Function in Health and Disease

Heparan sulfate is a ubiquitous, variably sulfated interactive glycosaminoglycan that consists of repeating disaccharides of glucuronic acid and glucosamine that are subject to a number of modifications (acetylation, de-acetylation, epimerization, sulfation). Variable heparan sulfate chain lengths and sequences within the heparan sulfate chains provide structural diversity generating interactive oligosaccharide binding motifs with a diverse range of extracellular ligands and cellular receptors providing instructional cues over cellular behaviour and tissue homeostasis through the regulation of essential physiological processes in development, health, and disease. heparan sulfate and heparan sulfate-PGs are integral components of the specialized glycocalyx surrounding cells. Heparan sulfate is the most heterogeneous glycosaminoglycan, in terms of its sequence and biosynthetic modifications making it a difficult molecule to fully characterize, multiple ligands also make an elucidation of heparan sulfate functional properties complicated. Spatio-temporal presentation of heparan sulfate sulfate groups is an important functional determinant in tissue development and in cellular control of wound healing and extracellular remodelling in pathological tissues. The regulatory properties of heparan sulfate are mediated via interactions with chemokines, chemokine receptors, growth factors and morphogens in cell proliferation, differentiation, development, tissue remodelling, wound healing, immune regulation, inflammation, and tumour development. A greater understanding of these HS interactive processes will improve therapeutic procedures and prognoses. Advances in glycosaminoglycan synthesis and sequencing, computational analytical carbohydrate algorithms and advanced software for the evaluation of molecular docking of heparan sulfate with its molecular partners are now available. These advanced analytic techniques and artificial intelligence offer predictive capability in the elucidation of heparan sulfate conformational effects on heparan sulfate-ligand interactions significantly aiding heparan sulfate therapeutics development.

Single-cell transcriptomic analysis identifies an immune-prone population in erythroid precursors during human ontogenesis

Nonimmune cells can have immunomodulatory roles that contribute to healthy development. However, the molecular and cellular mechanisms underlying the immunomodulatory functions of erythroid cells during human ontogenesis remain elusive. Here, integrated, single-cell transcriptomic studies of erythroid cells from the human yolk sac, fetal liver, preterm umbilical cord blood (UCB), term UCB and adult bone marrow (BM) identified classical and immune subsets of erythroid precursors with divergent differentiation trajectories. Immune-erythroid cells were present from the yolk sac to the adult BM throughout human ontogenesis but failed to be generated in vitro from human embryonic stem cells. Compared with classical-erythroid precursors, these immune-erythroid cells possessed dual erythroid and immune regulatory networks, showed immunomodulatory functions and interacted more frequently with various innate and adaptive immune cells. Our findings provide important insights into the nature of immune-erythroid cells and their roles during development and diseases.

Protein Posttranslational Signatures Identified in COVID-19 Patient Plasma

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a highly contagious virus of the coronavirus family that causes coronavirus disease-19 (COVID-19) in humans and a number of animal species. COVID-19 has rapidly propagated in the world in the past 2 years, causing a global pandemic. Here, we performed proteomic analysis of plasma samples from COVID-19 patients compared to healthy control donors in an exploratory study to gain insights into protein-level changes in the patients caused by SARS-CoV-2 infection and to identify potential proteomic and posttranslational signatures of this disease. Our results suggest a global change in protein processing and regulation that occurs in response to SARS-CoV-2, and the existence of a posttranslational COVID-19 signature that includes an elevation in threonine phosphorylation, a change in glycosylation, and a decrease in arginylation, an emerging posttranslational modification not previously implicated in infectious disease. This study provides a resource for COVID-19 researchers and, longer term, and will inform our understanding of this disease and its treatment.

Association between Serum Serglycin Levels and St-Segment Elevation Myocardial Infarction

Fundamento:

Sugere-se que a serglicina tenha funções importantes na estabilização da fibrina e inflamação, mas há informações limitadas sobre seu valor clínico para a doença cardíaca aterosclerótica.

Objetivo:

O objetivo do presente estudo é descobrir os níveis séricos de serglicina em pacientes com infarto agudo do miocárdio e nos indivíduos do grupo controle; e investigar a associação entre os níveis de serglicina com marcadores de inflamação e marcadores de tamanho do infarto.

Métodos:

A população do estudo consistiu em 75 pacientes com infarto do miocárdio com supradesnivelamento do segmento ST (IAMCSST) e 57 pacientes com artérias coronárias normais (NCA) (grupo controle). As características dos pacientes, os níveis séricos de serglicina, os níveis de proteína C-reativa ultrassensível (PCR-us), os níveis máximos de troponina T e outros parâmetros bioquímicos foram registrados. O valor de p<0,05 foi considerado estatisticamente significativo.

Resultados:

O grupo controle consistiu em indivíduos mais jovens e que fumam menos do que os do grupo IAMCSST. O número de mulheres no grupo controle foi maior do que no grupo IAMCSST. Os níveis séricos de serglicina foram significativamente maiores no grupo IAMCSST do que no grupo controle (102,81±39,42 vs. 57,13±32,25, p<0,001). As análises de correlação revelaram uma correlação positiva significativa entre a serglicina e a troponina (correlação de postos de Spearman: 0,419; p<0,001) e entre a serglicina e a proteína C-reativa ultrassensível (correlação de postos de Spearman: 0,336; p<0,001). A análise de regressão logística multivariada demonstrou que os níveis séricos de serglicina apresentaram-se independentemente associados com IAMCSST. Usando um nível de corte de 80,47 μg/L, o nível de serglicina foi preditor da presença de IAMCSST com uma sensibilidade de 75,7% e especificidade de 68,4%.

Conclusão:

Os níveis séricos de serglicina apresentaram-se significativamente maiores no grupo IAMCSST do que no grupo controle. Os níveis de serglicina sérica mostraram-se positivamente correlacionados com os níveis de proteína C-reativa ultrassensível e troponina.

Three-Dimensional Models as a New Frontier for Studying the Role of Proteoglycans in the Normal and Malignant Breast Microenvironment

The extracellular matrix (ECM) provides cues to direct mammogenesis, tumourigenesis and metastatic processes. Over the past several decades, two-dimensional (2D) culture models have been invaluable in furthering our understanding of the tumor microenvironment (TME), however, they still do not accurately emulate the associated biological complexities. In contrast, three-dimensional (3D) culture models provide a more physiologically relevant platform to study relevant physicochemical signals, stromal-epithelial cell interactions, vascular and immune components, and cell-ECM interactions in the human breast microenvironment. A common thread that may weave these multiple interactions are the proteoglycans (PGs), a prominent family of molecules in breast tissue. This review will discuss how these PGs contribute to the breast cancer TME and provide a summary of the traditional and emerging technologies that have been utilized to better understand the role of PGs during malignant transformation. Furthermore, this review will emphasize the differences that PGs exhibit between normal tissues and tumor ECM, providing a rationale for the investigation of underexplored roles of PGs in breast cancer progression using state-of-the-art 3D culture models.

Heparan Sulfate Proteoglycans Biosynthesis and Post Synthesis Mechanisms Combine Few Enzymes and Few Core Proteins to Generate Extensive Structural and Functional Diversity

Glycosylation is a common and widespread post-translational modification that affects a large majority of proteins. Of these, a small minority, about 20, are specifically modified by the addition of heparan sulfate, a linear polysaccharide from the glycosaminoglycan family. The resulting molecules, heparan sulfate proteoglycans, nevertheless play a fundamental role in most biological functions by interacting with a myriad of proteins. This large functional repertoire stems from the ubiquitous presence of these molecules within the tissue and a tremendous structural variety of the heparan sulfate chains, generated through both biosynthesis and post synthesis mechanisms. The present review focusses on how proteoglycans are “gagosylated” and acquire structural complexity through the concerted action of Golgi-localized biosynthesis enzymes and extracellular modifying enzymes. It examines, in particular, the possibility that these enzymes form complexes of different modes of organization, leading to the synthesis of various oligosaccharide sequences.

Molecular Interactions Stabilizing the Promatrix Metalloprotease-9·Serglycin Heteromer

Previous studies have shown that THP-1 cells produced an SDS-stable and reduction-sensitive complex between proMMP-9 and a chondroitin sulfate proteoglycan (CSPG) core protein. The complex could be reconstituted in vitro using purified serglycin (SG) and proMMP-9 and contained no inter-disulfide bridges. It was suggested that the complex involved both the FnII module and HPX domain of proMMP-9. The aims of the present study were to resolve the interacting regions of the molecules that form the complex and the types of interactions involved. In order to study this, we expressed and purified full-length and deletion variants of proMMP-9, purified CSPG and SG, and performed in vitro reconstitution assays, peptide arrays, protein modelling, docking, and molecular dynamics (MD) simulations. ProMMP-9 variants lacking both the FnII module and the HPX domain did not form the proMMP-9∙CSPG/SG complex. Deletion variants containing at least the FnII module or the HPX domain formed the proMMP-9∙CSPG/SG complex, as did the SG core protein without CS chains. The interacting parts covered large surface areas of both molecules and implicated dynamic and complementary ionic, hydrophobic, and hydrogen bond interactions. Hence, no short single interacting linear motifs in the two macromolecules could explain the strong SDS-stable and reduction-sensitive binding.

SRGN crosstalks with YAP to maintain chemoresistance and stemness in breast cancer cells by modulating HDAC2 expression

Background: Chemoresistance is a significant obstacle to the effective treatment of breast cancer (BC), resulting in more aggressive behavior and worse clinical outcome. The molecular mechanisms underlying breast cancer chemoresistance remain unclear. Our microarray analysis had identified the overexpression of a small molecular glycoprotein serglycin (SRGN) in multidrug-resistant BC cells. Here, we aimed to investigate the role of SRGN in chemoresistance of breast cancer and elucidate the underlying mechanisms. Methods: SRNG overexpression was identified using microarray analysis and its clinical relevance was analyzed. To investigate the role of SRGN, we performed various in vitro and in vivo studies, as well as characterization of serum and tissue samples from BC patients. Chemosensitivity measurement, gene expression interference, immunofluorescence staining, mammosphere assay, flow cytometry analysis, luciferase reporter assay, ChIP-qPCR, coimmunoprecipitation, and immunohistochemistry were performed to explore the potential functions and mechanisms of SRGN. Results: We confirmed overexpression of SRGN in chemoresistant BC cells and in serum and tissue samples from BC patients with poor response to chemotherapy. SRGN specifically predicted poor prognosis in BC patients receiving chemotherapy. Mechanistically, SRGN promoted chemoresistance both in vitro and in vivo by cross-talking with the transcriptional coactivator YES-associated protein (YAP) to maintain stemness in BC cells. Ectopic YAP expression restored the effects of SRGN knockdown. Inversely, YAP knockdown rescued the effects of SRGN overexpression. The secreted SRGN triggered ITGA5/FAK/CREB signaling to enhance YAP transcription. Reciprocally, YAP promoted SRGN transcription in a TEAD1-dependent manner to form a feed-forward circuit. Moreover, the YAP/RUNX1 complex promoted HDAC2 transcription to induce chemoresistance and stemness in BC cells. Importantly, the SRGN levels were positively correlated with the YAP and HDAC2 levels in chemoresistant BC tissues. YAP and HDAC2 acted downstream of SRNG and correlated with poor outcomes of BC patients receiving chemotherapy. Conclusions: Our findings clarify the roles and mechanisms of SRGN in mediating chemoresistance in breast cancer and suggest its use a potential biomarker for chemotherapeutic response. We believe that novel therapeutic strategies for breast cancer can be designed by targeting the signaling mediated by the crosstalk between SRGN and YAP.

Increased levels of serum serglycin and agrin is associated with adverse perinatal outcome in early onset preeclampsia

Goal: Our aim was to determine whether alterations in serum serglycin and agrin levels in early-onset preeclampsia (EOPE) are useful in predicting adverse perinatal outcomes such as fetal growth restriction (FGR), intrauterine fetal demise (IUFD), preterm delivery and/or neonatal unit admission. Materials and Methods: A prospective case-controlled study enrolled 88 pregnant patients (44 EOPE and 44 controls). Maternal serum serglycin and agrin levels were determined before the 34th gestational week by enzyme-linked immunosorbent assay. Results: Compared with controls, women with EOPE had significantly higher serglycin and agrin levels (p = .018; p = .048). Multivariable logistic regression analysis revealed serglycin was independently associated with FGR in EOPE (OR 0.866; 95% CI 0.779-0.953). Agrin was independently associated with IUFD in EOPE (OR 0.757, 95% CI 0.636-0.879). Conclusions: The current study suggests that increased maternal serum serglycin is associated with FGR, and increased maternal serum agrin is associated with IUFD in EOPE.

Serglycin as part of IL-1β induced inflammation in human chondrocytes

Serglycin (SRGN) is an intracellular proteoglycan produced and secreted by several cell types. The increased expression of SRGN was associated with greater aggressiveness in cancer and inflammation. In this study, we demonstrated that SRGN is increased in human chondrocytes after IL-β stimulation. Furthermore, we found that secreted SRGN was able to bind the CD44 receptor thus participating in the extension of the inflammatory response. Using SRGN knockdown cells we observed a significantly decrease in specific inflammatory markers and NF-kB activation. Similar results were observed by blocking the CD44 receptor. These data provide further evidences for a direct involvement of SRGN in the mechanisms regulating the non-infectious chondrocytes damage, and the consequent joint inflammation and cartilage destruction in arthritis.

The role of increased synovial fluid A disintegrin and metalloproteinase with thrombospondin motifs4 and serglycin levels in osteoarthritis

BACKGROUND

The first research to determine synovial fluid ADAMTS4 and serglycin levels in osteoarthritis and OA progression.

AIM

We aimed to determine ADAMTS4 and serglycin levels, interactions, and changes in the synovial fluid of knee OA, and also to determine effective in OA progression.

METHODS

A case-control study was carried out including a total of 88 participants (29 patients late OA [LOA], 28 early OA [EOA], and 30 controls). Synovial fluid serglycin and ADAMTS4 levels were measured by commercially available ELISA kits, and knee functions of the patients were evaluated with The Western Ontario and McMaster Universities Osteoarthritis score (WOMAC). Logistic regression analysis was applied for the associated with progression of OA.

RESULTS

Synovial fluid ADAMTS4 and serglycin levels were significantly higher in LOA than EOA and control groups (p < .001 and p < .001; p = .038 and p = .007, respectively). All parameters were evaluated after adjustment for age. LOA patients had significantly higher levels of WOMAC score than EOA and controls (p < .001 and p < .001). According to the logistic regression analysis, synovial fluid ADAMTS4, serglycin levels, and WOMAC score were found to be significantly associated with progression of OA.

Unconventional protein secretion – new insights into the pathogenesis and therapeutic targets of human diseases

Most secretory proteins travel through a well-documented conventional secretion pathway involving the endoplasmic reticulum (ER) and the Golgi complex. However, recently, it has been shown that a significant number of proteins reach the plasma membrane or extracellular space via unconventional routes. Unconventional protein secretion (UPS) can be divided into two types: (i) the extracellular secretion of cytosolic proteins that do not bear a signal peptide (i.e. leaderless proteins) and (ii) the cell-surface trafficking of signal-peptide-containing transmembrane proteins via a route that bypasses the Golgi. Understanding the UPS pathways is not only important for elucidating the mechanisms of intracellular trafficking pathways but also has important ramifications for human health, because many of the proteins that are unconventionally secreted by mammalian cells and microorganisms are associated with human diseases, ranging from common inflammatory diseases to the lethal genetic disease of cystic fibrosis. Therefore, it is timely and appropriate to summarize and analyze the mechanisms of UPS involvement in disease pathogenesis, as they may be of use for the development of new therapeutic approaches. In this Review, we discuss the intracellular trafficking pathways of UPS cargos, particularly those related to human diseases. We also outline the disease mechanisms and the therapeutic potentials of new strategies for treating UPS-associated diseases.

Heparan Sulfate Proteoglycans in Human Colorectal Cancer

Colorectal cancer is the third most common cancer worldwide, accounting for more than 610,000 mortalities every year. Prognosis of patients is highly dependent on the disease stage at diagnosis. Therefore, it is crucial to investigate molecules involved in colorectal cancer tumorigenesis, with possible use as tumor markers. Heparan sulfate proteoglycans are complex molecules present in the cell membrane and extracellular matrix, which play vital roles in cell adhesion, migration, proliferation, and signaling pathways. In colorectal cancer, the cell surface proteoglycan syndecan-2 is upregulated and increases cell migration. Moreover, expression of syndecan-1 and syndecan-4, generally antitumor molecules, is reduced. Levels of glypicans and perlecan are also altered in colorectal cancer; however, their role in tumor progression is not fully understood. In addition, studies have reported increased heparan sulfate remodeling enzymes, as the endosulfatases. Therefore, heparan sulfate proteoglycans are candidate molecules to clarify colorectal cancer tumorigenesis, as well as important targets to therapy and diagnosis.

Biodiversity of CS–proteoglycan sulphation motifs: chemical messenger recognition modules with roles in information transfer, control of cellular behaviour and tissue morphogenesis

Chondroitin sulphate (CS) glycosaminoglycan chains on cell and extracellular matrix proteoglycans (PGs) can no longer be regarded as merely hydrodynamic space fillers. Overwhelming evidence over recent years indicates that sulphation motif sequences within the CS chain structure are a source of significant biological information to cells and their surrounding environment. CS sulphation motifs have been shown to interact with a wide variety of bioactive molecules, e.g. cytokines, growth factors, chemokines, morphogenetic proteins, enzymes and enzyme inhibitors, as well as structural components within the extracellular milieu. They are therefore capable of modulating a panoply of signalling pathways, thus controlling diverse cellular behaviours including proliferation, differentiation, migration and matrix synthesis. Consequently, through these motifs, CS PGs play significant roles in the maintenance of tissue homeostasis, morphogenesis, development, growth and disease. Here, we review (i) the biodiversity of CS PGs and their sulphation motif sequences and (ii) the current understanding of the signalling roles they play in regulating cellular behaviour during tissue development, growth, disease and repair.

SRGN-TGFβ2 regulatory loop confers invasion and metastasis in triple-negative breast cancer

Patients with triple-negative breast cancers (TNBC) are at a high risk for a recurrent or metastatic disease, and the molecular mechanisms associated with this risk are unclear. Proteoglycan serglycin (SRGN) proteins are involved in tumor metastasis, but their role in TNBC has not yet been elucidated. This study investigates the SRGN gene expression and how it regulates TGFβ2 and the downstream signaling of TGFβ2 in TNBC cells and tissues. Our results show that SRGN mRNA and protein expression levels were significantly higher in TNBC cell lines and tumor tissues than that in non-TNBC cells and tissues. We inhibited SRGN expression and protein secretion using shRNA and we observed this inhibited the invasive motility of TNBC cancer cells in vitro and metastasis of TNBC cancer cells in vivo. SRGN protein treatment increased the expression and secretion of transforming growth factor-β2 (TGFβ2) by activating CD44/CREB1 signaling and promoted epithelial-to-mesenchymal transition in TNBC cells. Moreover, TGFβ2 treatment increased the mRNA and protein expression of the SRGN gene by activating Smad3 to target the SRGN relative promoter domain in TNBC cells. Our findings demonstrate that SRGN interacts with TGFβ2 which regulates TNBC metastasis via the autocrine and paracrine routes. SRGN could serve as a potential target for development of agents or therapeutics for the TNBC.

Serglycin: at the crossroad of inflammation and malignancy

Serglycin has been initially characterized as an intracellular proteoglycan expressed by hematopoietic cells. All inflammatory cells highly synthesize serglycin and store it in granules, where it interacts with numerous inflammatory mediators, such as proteases, chemokines, cytokines, and growth factors. Serglycin is implicated in their storage into the granules and their protection since they are secreted as complexes and delivered to their targets after secretion. During the last decade, numerous studies have demonstrated that serglycin is also synthesized by various non-hematopoietic cell types. It has been shown that serglycin is highly expressed by tumor cells and promotes their aggressive phenotype and confers resistance against drugs and complement system attack. Apart from its direct beneficial role to tumor cells, serglycin may promote the inflammatory process in the tumor cell microenvironment thus enhancing tumor development. In the present review, we discuss the role of serglycin in inflammation and tumor progression.

Serglycin (SRGN) overexpression predicts poor prognosis in hepatocellular carcinoma patients. Med Oncol. 2013;30:707. [PMID: 23996242 DOI: 10.1007/s12032-013-0707-4]

Hepatocellular carcinoma (HCC) is known for its high rate of recurrence and poor prognosis, which makes it necessary to identify new predictive markers for HCC and to explore the underlying mechanism(s). Emerging evidence suggests that the proteoglycan serglycin (SRGN) might play a crucial role in tumor metastasis. However, currently, the function of SRGN in HCC remains unknown. Here, we evaluated the expression pattern of SRGN in 127 HCC specimens and their adjacent, non-tumorous tissues using immunohistochemical assays. We observed that SRGN was significantly upregulated in HCC tissues. Elevated expression levels of SRGN were detectable in 72/127 (56.7%) of the HCC specimens and in 4/127 (3.1%) of adjacent non-tumorous tissues (p < 0.001). Further correlation analysis demonstrated that the increased expression of SRGN was positively associated with HBV infection, GGT level, vascular invasion, advanced BCLC stage and early recurrence (p < 0.05). Increased SRGN expression correlated with unfavorable prognosis in HCC patients. In multivariate analyses, SRGN expression levels were found to represent an independent predictor for overall survival (p = 0.002) and time to recurrence (p = 0.010) of HCC patients. Furthermore, the elevated expression of SRGN in the HCC tissues was accompanied by elevated levels of vimentin and the absence of E-cadherin. Similarly, the reduced expression of SRGN was accompanied by elevated levels of E-cadherin and the absence of vimentin. E-cadherin and vimentin are well-accepted biomarkers of the epithelial-mesenchymal transition (EMT), and the expression of SRGN might correlate with EMT. Our results demonstrate that the elevated expression of SRGN represents a crucial event in HCC patients that is indicative of poor clinical outcome.

Organization of the neuroepithelial actin cytoskeleton is regulated by heparan sulfation during neurulation

Heparan sulfate and cytoskeletal actin microfilaments have both been shown to be important regulators of neural tube closure during embryonic development. To determine the functional relationship of these two molecules in formation of the spinal neural tube, we cultured ARC mouse embryos at embryonic day E8.5 in the presence of chlorate, a competitive inhibitor of glycosaminoglycan sulfation, and examined the effects on organization of actin microfilaments in the neuroepithelium. Compared against embryos cultured under control conditions, chlorate-treated embryos had shortened posterior neuropore, a loss of median hinge point formation and increased bending at the paired dorsolateral hinge points. Furthermore, apical organization of actin microfilaments in the neuroepithelial cells was absent, and this was associated with convex bending of the neuroepithelium. The results suggest that heparan sulfate is an important determinant of cytoskeletal actin organization during spinal neurulation, and that its biological action is dependent on sulfation of the heparan molecule.