The Structural Basis for Lipid and Endotoxin Binding in RP105-MD-1, and Consequences for Regulation of Host Lipopolysaccharide Sensitivity

Ortiz-Suarez, Maite L.; Bond, Peter J.

doi:10.1016/j.str.2015.10.021

Cited by 12 publications

(12 citation statements)

References 54 publications

(127 reference statements)

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“…One matched the bound state observed in the X-ray structure (Park et al, 2009), while in the opposite orientation the glucosamine disaccharide was rotated by 180 . The population of the latter orientation, in addition to the crystallographic state, is consistent with observations of nuclear magnetic resonance (NMR) cross-peaks for labeled endotoxin (Yu et al, 2012) and has been observed for the closely related MD-1 protein (Ortiz-Suarez and Bond, 2016). In a typical ''productive'' binding simulation, the lipid A molecule rapidly settled within the MD-2 pocket, and a native-like state was observed after $80 ns.…”

Section: Assembly Of the Lipid A/md-2 Complexsupporting

confidence: 85%

A Thermodynamic Funnel Drives Bacterial Lipopolysaccharide Transfer in the TLR4 Pathway

et al. 2018

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The Gram-negative bacterial outer membrane contains lipopolysaccharide, which potently stimulates the mammalian innate immune response. This involves a relay of specialized complexes culminating in transfer of lipopolysaccharide from CD14 to Toll-like receptor 4 (TLR4) and its co-receptor MD-2 on the cell surface, leading to activation of downstream inflammatory responses. In this study we develop computational models to trace the TLR4 cascade in near-atomic detail. We demonstrate through rigorous thermodynamic calculations that lipopolysaccharide molecules traversing the receptor cascade fall into a thermodynamic funnel. An affinity gradient for lipopolysaccharide is revealed upon extraction from aggregates or realistic bacterial outer membrane models and transfer through CD14 to the terminal TLR4/MD-2 receptor-co-receptor complex. We subsequently assemble viable CD14/TLR4/MD-2 oligomers at the plasma membrane surface, and observe lipopolysaccharide exchange between CD14 and TLR4/MD-2. Collectively, this work helps to unravel the key structural determinants governing endotoxin recognition in the TLR4 innate immune pathway.

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Section: Assembly Of the Lipid A/md-2 Complexsupporting

confidence: 85%

A Thermodynamic Funnel Drives Bacterial Lipopolysaccharide Transfer in the TLR4 Pathway

et al. 2018

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“…The structural difference between MD-1 and MD-2 explains the low affinity of MD-1, which has a shallower cavity for direct binding to LPS (39). However, a recent crystallographic study demonstrates the structural basis for lipid and endotoxin binding to the CD180/MD-1 complex through a series of atomically detailed molecular simulations (40). The MD-1 cavity was expanded by a decrease in entropy to accommodate endotoxin binding, such that the CD180/MD-1 complex acts as a sink and source of LPS for TLR4.…”

Section: Discussionmentioning

confidence: 99%

Myeloma Cells Are Activated in Bone Marrow Microenvironment by the CD180/MD-1 Complex, Which Senses Lipopolysaccharide

et al. 2018

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Multiple myeloma (MM) cells acquire dormancy and drug resistance via interaction with bone marrow stroma cells (BMSC) in a hypoxic microenvironment. Elucidating the mechanisms underlying the regrowth of dormant clones may contribute to further improvement of the prognosis of MM patients. In this study, we find that the CD180/MD-1 complex, a noncanonical lipopolysaccharide (LPS) receptor, is expressed on MM cells but not on normal counterparts, and its abundance is markedly upregulated under adherent and hypoxic conditions. Bacterial LPS and anti-CD180 antibody, but not other Toll-like receptor ligands, enhanced the growth of MM cells via activation of MAP kinases ERK and JNK in positive correlation with expression levels of CD180. Administration of LPS significantly increased the number of CD180/CD138 double-positive cells in a murine xenograft model when MM cells were inoculated with direct attachment to BMSC. Knockdown of CD180 canceled the LPS response and Promoter analyses identified IKZF1 (Ikaros) as a pivotal transcriptional activator of the gene. Both cell adhesion and hypoxia activated transcription of the gene by increasing Ikaros expression and its binding to the promoter region. Pharmacological targeting of Ikaros by the immunomodulatory drug lenalidomide ameliorated the response of MM cells to LPS in a CD180-dependent manner and Thus, the CD180/MD-1 pathway may represent a novel mechanism of growth regulation of MM cells in a BM milieu and may be a therapeutic target of preventing the regrowth of dormant MM cells. This study describes a novel mechanism by which myeloma cells are regulated in the bone marrow, where drug resistance and dormancy can evolve after treatment, with potential therapeutic implications for treating this often untreatable blood cancer. .

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“…Our microarray data showed a substantial upregulation of CD14 and downregulation of CD180 in trophoblasts exposed to calcitriol. Notably, these proteins have opposite effects on the TLR4 response (Miyake 2003, Kelley et al 2013, Ortiz-Suarez & Bond 2016. CD14 is a TLR4 co-receptor (Jersmann 2005) and is expressed in two forms, one as a GPI-linked membrane protein and one as a soluble form (sCD14) present in serum.…”

Section: Response Of Cd14 and Cd180 To Calcitriolmentioning

confidence: 99%

“…Our data extend the understanding of the vitamin D-induced innate immune responses of human trophoblast by identifying a likely role for the upregulation of CD14, and downregulation of CD180, in response to calcitriol binding to the VDR in trophoblast. These two CD proteins influence the cellular TLR4 response in opposite directions (Ortiz-Suarez & Bond 2016). TLRs are expressed in many epithelia (Gay et al 2014) including human trophoblasts, and multiple bacterial products, including LPS, activate TLR4.…”

Section: Figurementioning

confidence: 99%

“…We assessed the response of primary cultures of human trophoblasts to calcitriol and used whole-genome microarrays to identify hypothesis-generating changes in gene expression. Notably, the microarray identified a marked inverse effect of calcitriol on gene expression for two immunomodulators, CD14 and CD180/RP105 (hereafter designated CD180), both of which regulate tolllike receptor 4 (TLR4)-mediated responses to bacterial ligands (Kelley et al 2013, Gay et al 2014, Ortiz-Suarez & Bond 2016. We then tested the hypothesis that calcitriolupregulation of CD14 enhances the response of villous syncytiotrophoblasts to bacterial lipopolysaccharide (LPS).…”

Section: Introductionmentioning

confidence: 99%

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Calcitriol regulates immune genes CD14 and CD180 to modulate LPS responses in human trophoblasts

Longtine¹,

Cvitic²,

Colvin³

et al. 2017

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We assessed the response of primary cultures of placental villous mononucleated trophoblasts and multinucleated syncytiotrophoblast to calcitriol, the most biologically active form of vitamin D. Whole-genome microarray data showed that calcitriol modulates the expression of many genes in trophoblasts within 6 hours of exposure and RT-qPCR revealed similar responses in cytotrophoblasts, syncytiotrophoblasts and villous explants. Both cytotrophoblasts and syncytiotrophoblasts expressed genes for the vitamin D receptor, for LRP2 and CUBN that mediate internalization of calcidiol, for that encodes the enzyme that converts calcidiol into active calcitriol, and for that encodes the enzyme that modifies calcitriol and calcidiol to inactive calcitetrol. Notably, we found an inverse effect of calcitriol on expression of CD14 and CD180/RP105, proteins that differentially regulate toll-like receptor 4-mediated immune responses. Supported by gene ontology analysis, we tested the hypothesis that CD14 and CD180 modulate the inflammatory response of syncytiotrophoblast to bacterial lipopolysaccharide (LPS). These cells showed a robust response to a wide range of LPS concentrations, with induction of active NF-κB and increased secretion of IL-6 and IL-8. SiRNA-mediated knockdown of reduced the secretion of IL-6 and IL-8 in response to LPS. Collectively, our data showed that calcitriol has a rapid and widespread effect on villous trophoblast gene expression in general, and a specific effect on the innate immune response by syncytiotrophoblast.

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The Structural Basis for Lipid and Endotoxin Binding in RP105-MD-1, and Consequences for Regulation of Host Lipopolysaccharide Sensitivity

Cited by 12 publications

References 54 publications

A Thermodynamic Funnel Drives Bacterial Lipopolysaccharide Transfer in the TLR4 Pathway

A Thermodynamic Funnel Drives Bacterial Lipopolysaccharide Transfer in the TLR4 Pathway

Myeloma Cells Are Activated in Bone Marrow Microenvironment by the CD180/MD-1 Complex, Which Senses Lipopolysaccharide

Calcitriol regulates immune genes CD14 and CD180 to modulate LPS responses in human trophoblasts

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