Pyong Park - Profile on Academia.edu (original) (raw)

Papers by Pyong Park

Trends in Glycoscience and Glycotechnology, 2005

The epithelium plays a vital role in regulating tissue injury and inflammation because it frequen... more The epithelium plays a vital role in regulating tissue injury and inflammation because it frequently encounters and detects harmful agents that can initiate the inflammatory host response. The epithelium also elaborates cytokines, antimicrobial factors, proteinases, and other key inflammatory mediators, and regulates the recruitment of inflammatory cells to sites of tissue injury. Syndecan-1 is a major cell surface heparan sulfate proteoglycan of the epithelium that can bind and regulate many inflammatory factors through its heparan sulfate chains. Syndecan-1 expression and its secretion into the extracellular milieu by ectodomain shedding are regulated by various inflammatory mediators and pathological conditions. Recent data indicate that syndecan-1 protects the host from various non-infectious inflammatory disorders by coordinating epithelial cell proliferation and migration, neutralizing chemokines, attenuating exaggerated T lymphocyte homing, and by confining neutrophil migration to specific sites of tissue injury. However, several pathogens have devised schemes to take advantage of syndecan-1 to promote their pathogenesis. These findings indicate that syndecan-1 is a key molecule that modulates host responses to tissue injury in normal repair and in the pathogenesis of inflammatory diseases.

JCI insight, Sep 22, 2021

Infection and Immunity, Mar 1, 2006

Methods in Cell Biology, 2018

Syndecans comprise a major family of cell surface heparan sulfate proteoglycans (HSPGs). Syndecan... more Syndecans comprise a major family of cell surface heparan sulfate proteoglycans (HSPGs). Syndecans are composed of sulfated glycosaminoglycans (GAGs), heparan sulfate (HS) or both HS and chondroitin sulfate (CS), attached covalently to core proteins. Syndecans regulate many cellular processes, such as adhesion, proliferation, and migration. Syndecans bind and regulate molecules primarily through their HS chains, but do not bind to all HS/heparin-binding molecules. Furthermore, mice ablated for the syndecan-1 or -4 gene do not show major developmental abnormalities, but they do show striking pathological phenotypes when challenged with infectious or inflammatory stimuli and conditions, suggesting that certain functions of syndecans are specific and cannot be compensated for by other syndecans or other HSPGs. These observations underscore the physiological importance of syndecans and indicate a need to study the activities of isolated native syndecans to define their molecular and cellular functions, and to establish their biological significance. Here we describe methods to isolate syndecans and several assays to analyze their functions.

Shock, Nov 1, 2015

We have shown in a rodent model of hemorrhagic shock (HS) that fresh frozen plasma (FFP) reduces ... more We have shown in a rodent model of hemorrhagic shock (HS) that fresh frozen plasma (FFP) reduces lung inflammation and injury which are correlated with restitution of syndecan-1. Since the gut is believed to contribute to distant organ injury and inflammation after shock, the current study sought to determine if the protective effects of plasma would extend to the gut and to elucidate the contribution of syndecan-1 to this protective effect. We also examined the potential role of TNFα, and a disintegrin and metalloproteinase (ADAM)-17, both intestinal sheddases of syndecan-1. Wild-type (WT) and syndecan-1 -/-(KO) mice were subjected to HS followed by resuscitation with lactated ringers (LR) or FFP and compared to shock alone and shams. Small bowel and blood were obtained after 3 hours for analysis of mucosal injury and inflammation and TNFα and ADAM-17 protein expression and activity. After HS, gut injury and inflammation were significantly increased compared to shams. Resuscitation with LR decreased both injury and inflammation which were further lessened by FFP. KO mice displayed worsened gut injury and inflammation after HS compared to WT mice, and LR and FFP equivalently inhibited injury and inflammation. Both systemic and intestinal TNFα and ADAM-17 followed similar trends, with increases after HS, reduction by LR, and a further decrease by FFP in WT but not KO mice. In conclusion, FFP decreased gut injury and inflammation after hemorrhagic shock, an effect that was abrogated in syndecan-1 -/-mice. Plasma also decreased TNFα and ADAM-17, representing a potential mechanistic link to its protection via syndecan-1.

Shock, Sep 1, 2017

Syndecan-1 is considered a biomarker of injury to the endothelial glycocalyx following hemorrhagi... more Syndecan-1 is considered a biomarker of injury to the endothelial glycocalyx following hemorrhagic shock, with shedding of sdc1 deleterious. Resuscitation with fresh frozen plasma (FFP) has been correlated with restitution of pulmonary sdc1 and reduction of lung injury, but the precise contribution of sdc1 to FFPs protection in the lung remains unclear. Human lung endothelial cells were used to assess the time and dose dependent effect of FFP on sdc1 expression and the effect of sdc1 silencing on in vitro endothelial cell permeability and actin stress fiber formation. Wild-type (WT) and syndecan-1 -/-mice were subjected to hemorrhagic shock followed by resuscitation with lactated ringers (LR) or FFP and compared to shock alone and shams. Lungs were harvested after 3 hours for analysis of permeability, histology, and inflammation and for measurement of syndecan-2 and 4 expression. In vitro, FFP enhanced pulmonary endothelial sdc1 expression in time-and dose-dependent manners and loss of sdc1 in pulmonary endothelial cells worsened permeability and stress fiber formation by FFP. Loss of sdc1 in vivo lead to equivalency between LR and FFP in restoring pulmonary injury, inflammation, and permeability after shock. Lastly, sdc1 -/-mice demonstrated a significant increase in pulmonary syndecan 4 expression after hemorrhagic shock and FFP based resuscitation. Taken together, our findings support a key role for sdc1 in modulating pulmonary protection by FFP after hemorrhagic shock. Our results also suggest that other members of the syndecan family may at least be contributing to FFP's effects on the endothelium, an area that warrants further investigation.

Microvascular Research, May 1, 2013

The existence of a hydrodynamically relevant endothelial glycocalyx has been established in capil... more The existence of a hydrodynamically relevant endothelial glycocalyx has been established in capillaries, venules, and arterioles in vivo. The glycocalyx is thought to consist primarily of membrane-bound proteoglycans with glycosaminoglycan side-chains, membrane-bound glypicans, and adsorbed plasma proteins. The proteoglycans found on the luminal surface of endothelial cells are syndecans-1, -2, and -4, and glypican-1. The extent to which any of these proteins might serve to anchor the glycocalyx to the endothelium has not yet been determined. To test whether syndecan-1, in particular, is an essential anchoring protein, we performed experiments to determine the hydrodynamically relevant glycocalyx thickness in syndecan-1 deficient (Sdc1-/-) mice. Micro-particle image velocimetry data were collected using a previously described method. Microviscometric analysis of these data consistently revealed the existence of a hydrodynamically relevant endothelial glycocalyx in Sdc1-/-mice in vivo. The mean glycocalyx thickness found in Sdc1-/-mice was 0.45±0.10 μm (N=15), as compared with 0.54±0.12 μm (N=11) in wild-type (WT) mice (p=0.03). The slightly thinner glycocalyx observed in Sdc1-/mice relative to WT mice may be due to the absence of syndecan-1. These findings show that healthy Sdc1-/-mice are able to synthesize and maintain a hydrodynamically relevant glycocalyx, which indicates that syndecan-1 is not an essential anchoring protein for the glycocalyx in Sdc1-/-mice. This may also be the case for WT mice; however, Sdc1-/-mice might adapt to the lack of syndecan-1 by increasing the expression of other proteoglycans. In any case, syndecan-1 does not appear to be a prerequisite for the existence of an endothelial glycocalyx.

Springer eBooks, Sep 24, 2014

Glycosaminoglycans (GAGs) have been shown to bind to a wide variety of microbial pathogens, inclu... more Glycosaminoglycans (GAGs) have been shown to bind to a wide variety of microbial pathogens, including viruses, bacteria, parasites, and fungi in vitro. GAGs are thought to promote pathogenesis by facilitating pathogen attachment, invasion, or evasion of host defense mechanisms. However, the role of GAGs in infectious disease has not been extensively studied in vivo and therefore their pathophysiological significance and functions are largely unknown. Here we describe methods to directly investigate the role of GAGs in infections in vivo using mouse models of bacterial lung and corneal infection. The overall experimental strategy is to establish the importance and specificity of GAGs, define the essential structural features of GAGs, and identify a biological activity of GAGs that promotes pathogenesis.

American Journal of Respiratory Cell and Molecular Biology, Aug 1, 2016

Although neutrophils play critical roles in innate immunity, in excess these cells cause severe t... more Although neutrophils play critical roles in innate immunity, in excess these cells cause severe tissue damage. Thus, neutrophil activation must be tightly regulated to prevent indiscriminant damage. Previously, we reported that mice lacking matrix metalloproteinase (MMP) 7 are protected from lung injury owing to markedly impaired neutrophil movement from the interstitium into mucosal lumenal spaces. This phenotype resulted from a lack of MMP7 shedding of syndecan-1, a heparan sulfate proteoglycan that carries the neutrophil chemokine CXCL1 as cargo. Here, we assessed if shedding syndecan-1/CXCL1 complexes affects neutrophil activation. Whereas injured monolayers of wild-type alveolar type II cells potently stimulated neutrophil activation, as gauged by release of myeloperoxidase, cells from Mmp7 2/2 or syndecan-1-null (Sdc1 2/2 ) mice or human cells with MMP7 knockdown did not. In vivo, we observed reduced myeloperoxidase release relative to neutrophil numbers in bleomycin-injured Mmp7 2/2 and Sdc1 2/2 mice. Furthermore, we determined that soluble syndecan-1 directly stimulated neutrophil activation in the absence of cellular damage. These data indicate that MMP7 shedding of syndecan-1/CXCL1 complexes functions as a checkpoint that restricts neutrophil activation at sites of epithelial injury.

American Journal of Pathology, Apr 1, 2008

Lactoferrin (LF) is an iron-binding protein found in milk, mucosal secretions, and the secondary ... more Lactoferrin (LF) is an iron-binding protein found in milk, mucosal secretions, and the secondary granules of neutrophils in which it is considered to be an important factor in the innate immune response against microbial infections. Moreover, LF deficiency in the secondary granules of neutrophils has long been speculated to contribute directly to the hypersusceptibility of specific granule deficiency (SGD) patients to severe, life-threatening bacterial infections. However, the exact physiological significance of LF in neutrophil-mediated host defense mechanisms remains controversial and has not yet been clearly established in vivo using relevant animal models. In this study, we used lactoferrin knockout (LFKO) mice to directly address the selective role of LF in the host defense response of neutrophils and to determine its contribution, if any, to the phenotype of SGD. Neutrophil maturation, migration, phagocytosis, granule release, and antimicrobial response to bacterial challenge were unaffected in LFKO mice. Interestingly, a stimulus-dependent defect in the oxidative burst response of LFKO neutrophils was observed in that normal activation was seen in response to opsonized bacteria whereas an impaired response was evident after phorbol myristate-13-acetate stimulation. Taken together, these results indicate that although LF deficiency alone is not a primary cause of the defects associated with SGD, this protein does play an immunomodulatory role in the oxidative burst response of neutrophils.

Expert Reviews in Molecular Medicine, Feb 1, 2010

Many microbial pathogens subvert proteoglycans for their adhesion to host tissues, invasion of ho... more Many microbial pathogens subvert proteoglycans for their adhesion to host tissues, invasion of host cells, infection of neighbouring cells, dissemination into the systemic circulation, and evasion of host defence mechanisms. Where studied, specific virulence factors mediate these proteoglycan-pathogen interactions, which are thus thought to affect the onset, progression and outcome of infection. Proteoglycans are composites of glycosaminoglycan (GAG) chains attached covalently to specific core proteins. Proteoglycans are expressed ubiquitously on the cell surface, in intracellular compartments, and in the extracellular matrix. GAGs mediate the majority of ligand-binding activities of proteoglycans, and many microbial pathogens elaborate cell-surface and secreted factors that interact with GAGs. Some pathogens also modulate the expression and function of proteoglycans through known virulence factors. Several GAG-binding pathogens can no longer attach to and invade host cells whose GAG expression has been reduced by mutagenesis or enzymatic treatment. Furthermore, GAG antagonists have been shown to inhibit microbial attachment and host cell entry in vitro and reduce virulence in vivo. Together, these observations underscore the biological significance of proteoglycan-pathogen interactions in infectious diseases.

Anatomical Record-advances in Integrative Anatomy and Evolutionary Biology, May 19, 2010

The extracellular domain of several membrane-anchored proteins is released from the cell surface ... more The extracellular domain of several membrane-anchored proteins is released from the cell surface as soluble proteins through a regulated proteolytic mechanism called ectodomain shedding. Cells use ectodomain shedding to actively regulate the expression and function of surface molecules, and modulate a wide variety of cellular and physiological processes. Ectodomain shedding rapidly converts membrane-associated proteins into soluble effectors and, at the same time, rapidly reduces the level of cell surface expression. For some proteins, ectodomain shedding is also a prerequisite for intramembrane proteolysis, which liberates the cytoplasmic domain of the affected molecule and associated signaling factors to regulate transcription. Ectodomain shedding is a process that is highly regulated by specific agonists, antagonists, and intracellular signaling pathways. Moreover, only about 2% of cell surface proteins are released from the surface by ectodomain shedding, indicating that cells selectively shed their protein ectodomains. This review will describe the molecular and cellular mechanisms of ectodomain shedding, and discuss its major functions in lung development and disease.

Veterinary Research, Oct 29, 2018

Streptococcus suis is a swine pathogen and zoonotic agent responsible for meningitis and septic s... more Streptococcus suis is a swine pathogen and zoonotic agent responsible for meningitis and septic shock. Although several putative virulence factors have been described, the initial steps of the S. suis pathogenesis remain poorly understood. While controversial results have been reported for a S. suis serotype 2 zinc metalloprotease (Zmp) regarding its IgA protease activity, recent phylogenetic analyses suggested that this protein is homologous to the ZmpC of Streptococcus pneumoniae, which is not an IgA protease. Based on the previously described functions of metalloproteases (including IgA protease and ZmpC), different experiments were carried out to study the activities of that of S. suis serotype 2. First, results showed that S. suis, as well as the recombinant Zmp, were unable to cleave human IgA 1 , confirming lack of IgA protease activity. Similarly, S. suis was unable to cleave P-selectin glycoprotein ligand-1 and to activate matrix metalloprotease 9, at least under the conditions tested. However, S. suis was able to partially cleave mucin 16 and syndecan-1 ectodomains. Experiments carried out with an isogenic Δzmp mutant showed that the Zmp protein was partially involved in such activities. The absence of a functional Zmp protein did not affect the ability of S. suis to adhere to porcine bronchial epithelial cells in vitro, or to colonize the upper respiratory tract of pigs in vivo. Taken together, our results show that S. suis serotype 2 Zmp is not a critical virulence factor and highlight the importance of independently confirming results on S. suis virulence by different teams.

Nature Communications, 2020

Intratumoral heterogeneity is a common feature of many myeloid leukemias and a significant reason... more Intratumoral heterogeneity is a common feature of many myeloid leukemias and a significant reason for treatment failure and relapse. Thus, identifying the cells responsible for residual disease and leukemia re-growth is critical to better understanding how they are regulated. Here, we show that a knock-in reporter mouse for the stem cell gene Musashi 2 (Msi2) allows identification of leukemia stem cells in aggressive myeloid malignancies, and provides a strategy for defining their core dependencies. Specifically, we carry out a high throughput screen using Msi2-reporter blast crisis chronic myeloid leukemia (bcCML) and identify several adhesion molecules that are preferentially expressed in therapy resistant bcCML cells and play a key role in bcCML. In particular, we focus on syndecan-1, whose deletion triggers defects in bcCML growth and propagation and markedly improves survival of transplanted mice. Further, live imaging reveals that the spatiotemporal dynamics of leukemia cells ...

Journal of Biological Chemistry, Jun 1, 2015

Background: Syndecan-1 promotes bacterial infections, but how this is accomplished remains unclea... more Background: Syndecan-1 promotes bacterial infections, but how this is accomplished remains unclear. Results: Syndecan-1 and 2-O-sulfated heparan compounds specifically enhanced S. aureus corneal virulence and inhibited bacterial killing by CRAMP secreted from degranulated neutrophils. Conclusion: Specific structural motifs in syndecan-1 HS promote S. aureus corneal infection by inhibiting neutrophil CRAMP. Significance: This study uncovers a new pathogenic role for syndecan-1 in bacterial infection. Ablation of syndecan-1 in mice is a gain of function mutation that enables mice to significantly resist infection by several bacterial pathogens. Syndecan-1 shedding is induced by bacterial virulence factors, and inhibition of shedding attenuates bacterial virulence, whereas administration of purified syndecan-1 ectodomain enhances virulence, suggesting that bacteria subvert syndecan-1 ectodomains released by shedding for their pathogenesis. However, the pro-pathogenic functions of syndecan-1 ectodomain have yet to be clearly defined. Here, we examined how syndecan-1 ectodomain enhances Staphylococcus aureus virulence in injured mouse corneas. We found that syndecan-1 ectodomain promotes S. aureus corneal infection in an HS-dependent manner. Surprisingly, we found that this propathogenic activity is dependent on 2-O-sulfated domains in HS, indicating that the effects of syndecan-1 ectodomain are structure-based. Our results also showed that purified syndecan-1 ectodomain and heparan compounds containing 2-O-sulfate motifs inhibit S. aureus killing by antimicrobial factors secreted by degranulated neutrophils, but does not affect intracellular phagocytic killing by neutrophils. Immunodepletion of antimicrobial factors with staphylocidal activities demonstrated that CRAMP, a cationic antimicrobial peptide, is primarily responsible for S. aureus killing among other factors secreted by degranulated neutrophils. Furthermore, we found that purified syndecan-1 ectodomain and heparan compounds containing 2-O-sulfate units potently and specifically inhibit S. aureus killing by synthetic CRAMP. These results provide compelling evidence that a specific subclass of sulfate groups, and not the overall charge of HS, permits syndecan-1 ectodomains to promote S. aureus corneal infection by inhibiting a key arm of neutrophil host defense.

Journal of Biological Chemistry, Dec 1, 2008

The ectodomain shedding of syndecan-1, a major cell surface heparan sulfate proteoglycan, modulat... more The ectodomain shedding of syndecan-1, a major cell surface heparan sulfate proteoglycan, modulates molecular and cellular processes central to the pathogenesis of inflammatory diseases. Syndecan-1 shedding is a highly regulated process in which outside-in signaling accelerates the proteolytic cleavage of syndecan-1 ectodomains at the cell surface. Several extracellular agonists that induce syndecan-1 shedding and metalloproteinases that cleave syndecan-1 ectodomains have been identified, but the intracellular mechanisms that regulate syndecan-1 shedding are largely unknown. Here we examined the role of the syndecan-1 cytoplasmic domain in the regulation of agonist-induced syndecan-1 shedding. Our results showed that the syndecan-1 cytoplasmic domain is essential because mutation of invariant cytoplasmic Tyr residues abrogates ectodomain shedding, but not because it is Tyr phosphorylated upon shedding stimulation. Instead, our data showed that the syndecan-1 cytoplasmic domain binds to Rab5, a small GTPase that regulates intracellular trafficking and signaling events, and this interaction controls the onset of syndecan-1 shedding. Syndecan-1 cytoplasmic domain bound specifically to Rab5 and preferentially to inactive GDP-Rab5 over active GTP-Rab5, and shedding stimulation induced the dissociation of Rab5 from the syndecan-1 cytoplasmic domain. Moreover, the expression of dominantnegative Rab5, unable to exchange GDP for GTP, interfered with the agonist-induced dissociation of Rab5 from the syndecan-1 cytoplasmic domain and significantly inhibited syndecan-1 shedding induced by several distinct agonists. Based on these data, we propose that Rab5 is a critical regulator of syndecan-1 shedding that serves as an on-off molecular switch through its alternation between the GDP-bound and GTP-bound forms.

Journal of Biological Chemistry, 2004

Coreceptor functions of cell surface heparan sulfate proteoglycans

American Journal of Physiology-cell Physiology, May 1, 2022

Receptor-ligand interactions play an important role in many biological processes by triggering sp... more Receptor-ligand interactions play an important role in many biological processes by triggering specific cellular responses. These interactions are frequently regulated by coreceptors that facilitate, alter, or inhibit signaling. Coreceptors work in parallel with other specific and accessory molecules to coordinate receptor-ligand interactions. Cell surface heparan sulfate proteoglycans (HSPGs) function as unique coreceptors because they can bind to many ligands and receptors through their HS and core protein motifs. Cell surface HSPGs are typically expressed in abundance of the signaling receptors and, thus, are capable of mediating the initial binding of ligands to the cell surface. HSPG coreceptors do not possess kinase domains or intrinsic enzyme activities and, for the most part, binding to cell surface HSPGs does not directly stimulate intracellular signaling. Because of these features, cell surface HSPGs primarily function as coreceptors for many receptor-ligand interactions. Given that cell surface HSPGs are widely conserved, they likely serve fundamental functions to preserve basic physiological processes. Indeed, cell surface HSPGs can support specific cellular interactions with growth factors, morphogens, chemokines, extracellular matrix (ECM) components, and microbial pathogens and their secreted virulence factors. Through these interactions, HSPG coreceptors regulate cell adhesion, proliferation, migration, and differentiation, and impact the onset, progression, and outcome of pathophysiological processes, such as development, tissue repair, inflammation, infection, and tumorigenesis. This review seeks to provide an overview of the various mechanisms of how cell surface HSPGs function as coreceptors.

Frontiers in Bioscience, Jun 1, 2016

Role of HSPGs in Systemic Bacterial Infections

Methods in molecular biology, Oct 10, 2021

Heparan sulfate proteoglycans (HSPGs) are at the forefront of host–microbe interactions. Cell sur... more Heparan sulfate proteoglycans (HSPGs) are at the forefront of host–microbe interactions. Cell surface HSPGs are thought to promote infection as attachment and internalization receptors for many bacterial pathogens and as soluble inhibitors of host immunity when released from the cell surface by ectodomain shedding. However, the importance of HSPG–pathogen interactions in vivo has yet to be clearly established. Here we describe several representative methods to study the role of HSPGs in systemic bacterial infections, such as bacteremia and sepsis. The overall experimental strategy is to use mouse models to establish the physiological significance of HSPGs, to determine the identity of HSPGs that specifically promote infection, and to define key structural features of HSPGs that enhance bacterial virulence in systemic infections.