Proteoglycan research最新文献

The lymphatic system is critical to the body's immune and circulatory system, and lymphangiogenesis, the development of new lymphatic vessels from pre-existing ones is a significant process capitalized upon by cancer during tumorigenesis. Decorin is a small leucine-rich proteoglycan which we have previously shown to be anti-tumorigenic and a suppressor of lymphangiogenesis. We have also shown that decorin exercises its anticancer properties through its ability to evoke autophagy. Through a comprehensive and unbiased proteomic analysis, we explored the implications of decorin exposure on protein expression within mouse lymphatic endothelial cells. We discovered that decorin enriches several protein pathways, notably proteasomal degradation and lysosomal pathways. Several proteins within these pathways such as lysosome associated membrane protein 1 (Lamp1) and Neural precursor cell expressed developmentally downregulated protein 8 (Nedd8) were differentially regulated following decorin treatment. These proteins and their functional pathways should be considered therapeutic targets and emerge as candidates for further exploration within the context of decorin and cancer suppression.

Neurexins are synaptic adhesion molecules best characterized in neurons, where they regulate synapse assembly and function, with emerging evidence indicating they are also abundantly expressed by astrocytes. To elucidate the interactome of NRXN1α, we employed a proximity labeling strategy in cultured human fetal glial cells (SVG p12 cells). This approach enables the identification of transient and spatially restricted protein interactions, offering insights into the molecular environment of NRXN1α in glia. Further, we investigated how the presence and number of glycosaminoglycan (GAG) chains present on NRXN1α influence these interactions by generating glycosylation-deficient mutants at previously characterized GAG glycosites. Here, we show that the astrocytic NRXN1α interactome in SVG p12 cells consists of over 400 proteins, half of which are likely modulated by GAGs. Our findings provide a systems-level view of NRXN1α-associated proteins in fetal glia cultured in the absence of neurons and highlight the role of GAG valency in modulating its interactome.

Cathelicidins are short cationic peptides with potent microbicidal activities and comprise an important arm of host innate immunity. Many cell types can produce cathelicidins, but they are mainly expressed by recruited immune cells and are induced in epithelial cells during infection. Although the mechanisms of bacterial killing by cathelicidins have been largely elucidated in vitro, those that regulate their activities in vivo are less well understood. Bacterial pathogens often co-opt host extracellular matrix (ECM) components and their functions to escape host defense; however, it is unclear whether such mechanisms exist against cathelicidins. Several studies have demonstrated that host heparan sulfate (HS) inhibits LL-37, the human cathelicidin, suggesting that bacteria might exploit HS to evade killing by cathelicidins. However, precisely how HS inhibits LL-37 and possibly other cathelicidins remains unknown, and the role of the HS-cathelicidin interaction in infectious disease has not been rigorously studied. Here, we found that deleting CRAMP, the murine cathelicidin, significantly increases the susceptibility of mice to Staphylococcus aureus corneal infection. We also determined that heparan compounds bind to CRAMP with low nanomolar affinity, the secondary structure of CRAMP is required for HS binding, and HS binding to CRAMP inhibits CRAMP binding to target bacterial cells. Furthermore, we found that heparan compounds inhibit the killing of S. aureus by cathelicidins derived from several mammalian species in a 2-O-sulfate-dependent manner. Additionally, we demonstrate for the first time that conditional deletion of HS2ST, the enzyme responsible for 2-O-sulfation of HS, in corneal epithelial cells significantly reduces the susceptibility of mice to corneal infection. Altogether, these data uncover an endogenous inhibition mechanism of cathelicidins where 2-O-sulfated epithelial HS tightly binds and neutralizes the antibacterial activity of cathelicidins.

Hyaluronan (HA) is a glycosaminoglycan synthesized at the cell membrane that can exist in numerous states in the extracellular matrix, including in ternary complexes with proteoglycans such as aggrecan and neurocan. HA synthesis is elevated following a wide variety of insults to the central nervous system (CNS) including neuroinflammatory disease, ischemia, and various forms of dementia. Recent studies have demonstrated that, in conjunction with increased HA synthesis, the expression and activities of hyaluronidases that digest HA are also elevated in the injured CNS. While high molecular weight forms of HA have their own functions that can be disrupted by hyaluronidases, digestion products of HA generated by these hyaluronidases have their own, distinct biological activities that can impact recovery from CNS damage. Here, we review some of the conditions and diseases in which hyaluronidase activity can play a role in preventing CNS repair and discuss the potential ways that hyaluronidase inhibitors could be used as therapeutic agents.

Hyaluronan (HA) is an essential glycosaminoglycan with supportive roles in hematopoiesis. HA is synthesized by hyaluronan synthases (HAS1, HAS2, and HAS3) and plays a crucial role in cellular signaling and extracellular matrix interactions. Megakaryocytes (MKs), the platelet progenitor cell, express only HAS2 and HAS3, and dysregulated metabolism of HA by MKs leads to thrombocytopenia. To unravel the contribution of HAS3 in platelet function, Using HAS1/3 knockout (dKO) mice, we demonstrate that thrombin-mediated activation is significantly impaired, whereas collagen-dependent activation remains intact. Functional assays indicate that platelet aggregation, integrin α_IIbβ3 activation, and granule secretion are reduced in HAS1/3 KO platelets. However, tail bleeding times remain normal, suggesting that primary hemostasis is not severely affected. Under flow conditions, dKO platelet adhesion to fibrinogen is deficient under venous shear, while adhesion under arterial shear is unaffected. Mechanistically, these impairments correlate with reduced phosphorylation of AKT (p-AKT), while phosphorylation of PLCγ (p-PLCγ) remains preserved, suggesting that expression of HAS3 selectively regulates platelet function. These findings highlight HA synthesis as a novel regulator of thrombin-induced platelet activation and suggest that HAS enzymes may be previously unknown modulators of hemostatic and thrombotic responses.

Glypicans (GPCs) are a family of cell surface proteoglycans involved in multiple signaling pathways that regulate cell fate and proliferation. They share a characteristic structure composed of a core protein with two or more heparan sulfate chains and a glycosyl-phosphatidylinositol anchor that attaches them to the cell membrane. Aberrant expression of certain glypicans such as GPC1, GPC2, and GPC3 has been found in multiple types of cancer and causes the dysregulation of Wnt, hedgehog, and other signaling pathways, making them emerging targets for cancer immunotherapy. The molecular mechanism by which glypicans interact with signaling factors will provide insights for the development of cancer therapeutics. However, the structural complexes of human glypicans with Wnt and other key signaling factors remain unsolved. In this brief review, we analyze the current protein structural evidence for glypicans, with an emphasis on their interaction with Wnt, in an effort to provide insights to understand the molecular mechanisms by which glypicans play positive or negative roles in Wnt signaling in cancer and to discuss their translational potentials.

Stabilin-2 is the primary scavenger for hyaluronan (HA) and binds to over two dozen other ligands including chondroitin sulfates, heparin, oxidized/acetylated LDL, etc. Although rat liver sinusoidal endothelial cells are the preferred primary cell lines and animal for physiological studies of Stab2/HARE, the rat recombinant protein has never been characterized. Since the rat Stab2/HARE has a high degree homology to mouse Stab2/HARE which has been cloned, our hypothesis is that the rat receptor is identical to mouse and very similar to the human receptor. Rat Stab2/HARE was cloned and expressed in the FlpIn HEK293 cell line. The recombinant protein was analyzed for HA and heparin binding/endocytosis as well as synthetic heparin (Dekaparin) in a mouse knockout model. The secreted ecto-domain was also created for surface plasmon resonance analysis. The physical structure of rat Stab2/HARE is different than human in that the small isoform is not expressed as robustly and reduction of the protein results in what is likely two physical conformational forms. Rat Stab2/HARE binding strength with HA is weaker when compared to human Stab2/HARE, but rate of endocytosis is higher. Heparin-Stab2/HARE bonding strength is similar to human, though endocytic rate tends to be higher. Metabolism of Dekaprin is delayed in a Stab2KO mouse model and affects liver sequestration of this drug. Rat Stab2/HARE has similar properties as the human Stab2/HARE with the exceptions that the rat recombinant protein has a different physical structure and has an increased HA and heparin internalization rate.

Solid tumors present a formidable challenge in oncology, necessitating innovative approaches to improve therapeutic outcomes. Proteoglycans, multifaceted molecules within the tumor microenvironment, have garnered attention due to their diverse roles in cancer progression. Their unique ability to interact with specific membrane receptors, growth factors, and cytokines provides a promising avenue for the development of recombinant proteoglycan-based therapies that could enhance the precision and efficacy of cancer treatment. In this study, we performed a comprehensive analysis of the proteoglycan gene landscape in human breast carcinomas. Leveraging the available wealth of genomic and clinical data regarding gene expression in breast carcinoma and using a machine learning model, we identified a unique gene expression signature composed of five proteoglycans differentially modulated in the tumor tissue: Syndecan-1 and asporin (upregulated) and decorin, PRELP and podocan (downregulated). Additional query of the breast carcinoma data revealed that serglycin, previously shown to be increased in breast carcinoma patients and mouse models and to correlate with a poor prognosis, was indeed decreased in the vast majority of breast cancer patients and its levels inversely correlated with tumor progression and invasion. This proteoglycan gene signature could provide novel diagnostic capabilities in breast cancer biology and highlights the need for further utilization of publicly available datasets for the clinical validation of preclinical experimental results.

The alveolus, the functional unit of the lung, is comprised of closely approximated alveolar epithelial and endothelial cells, across which gas exchange occurs. This alveolar septum also includes two substantial, intraluminal extracellular matrices: the alveolar epithelial and endothelial glycocalyces. This perspective investigates the distinct structures and homeostatic functions of these two glycocalyces, as well as their distinct fates and consequences during critical illnesses such as sepsis and the acute respiratory distress syndrome. We seek to identify key knowledge gaps, with the goal to inspire future mechanistic investigations that may substantially impact human health and disease.

Hyaluronan (HA) is one of the most abundant components of extracellular matrices. HA is a huge polysaccharide - a single linear HA polymer often exceeds 25,000 disaccharide units in length (~10⁷ Da) and occupies the volume of a 300 nm diameter sphere. These unique biochemical and biophysical properties are accompanied by extremely rapid turnover of HA, which emphasizes the importance of not only its biosynthesis but also degradation in regulating the homeostasis and biological functions of HA. Further supporting the specific importance of HA degradation, a large body of evidence demonstrates that biological functions of HA are dependent on its size and degree of fragmentation. While considerable research has revealed the roles of the HYAL family hyaluronidases in HA catabolism and biology, the discovery of TMEM2 as a functional cell surface hyaluronidase, coupled with increasing data demonstrating its remarkable biological functions, have added a new dimension of research to the field of HA biology.