| 1. |
- Broström, Julia M., et al.
(författare)
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Toluene diisocyanate exposure and autotaxin–lysophosphatidic acid signalling
- 2018
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 0041-008X .- 1096-0333. ; 355, s. 43-51
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Tidskriftsartikel (refereegranskat)abstract
- Toluene diisocyanate (TDI) is a reactive chemical used in manufacturing plastics. TDI exposure adversely affects workers' health, causing occupational asthma, but individuals differ in susceptibility. We recently suggested a role for signalling mediated by the enzyme autotaxin (ATX) and its product, lysophosphatidic acid (LPA), in TDI toxicity. Here we genotyped 118 TDI-exposed workers for six single-nucleotide polymorphisms (SNPs) in genes encoding proteins implicated in ATX–LPA signalling: purinergic receptor P2X7 (P2RX7), C–C motif chemokine ligand 2 (CCL2), interleukin 1β (IL1B), and caveolin 1 (CAV1). Two P2RX7 SNPs (rs208294 and rs2230911) significantly modified the associations between a biomarker of TDI exposure (urinary 2,4-toluene diamine) and plasma LPA; two IL1B SNPs (rs16944 and rs1143634) did not. CAV1 rs3807989 modified the associations, but the effect was not statistically significant (p = 0.05–0.09). In vitro, TDI-exposed bronchial epithelial cells (16HBE14o-) rapidly released ATX and IL-1β. P2X7 inhibitors attenuated both responses, but confocal microscopy showed non-overlapping localizations of ATX and IL-1β, and down-regulation of CAV1 inhibited the ATX response but not the IL-1β response. This study indicates that P2X7 is pivotal for TDI-induced ATX–LPA signalling, which was modified by genetic variation in P2RX7. Furthermore, our data suggest that the TDI-induced ATX and IL-1β responses occur independently.
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| 2. |
- Broström, Julia, et al.
(författare)
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Toluene diisocyanate: Induction of the autotaxin-lysophosphatidic acid axis and its association with airways symptoms.
- 2015
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Ingår i: Toxicology and Applied Pharmacology. - : Elsevier BV. - 1096-0333 .- 0041-008X. ; 287:3, s. 222-231
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Tidskriftsartikel (refereegranskat)abstract
- Diisocyanates are industrial chemicals which have a wide range of applications in developed and developing countries. They are notorious lung toxicants and respiratory sensitizers. However, the mechanisms behind their adverse effects are not adequately characterized. Autotaxin (ATX) is an enzyme producing lysophosphatidic acid (LPA), and the ATX-LPA axis has been implicated in lung related inflammatory conditions and diseases, including allergic asthma, but not to toxicity of environmental low-molecular-weight chemicals. We investigated effects of toluene diisocyanate (TDI) on ATX induction in human lung epithelial cell models, and we correlated LPA-levels in plasma to biomarkers of TDI exposure in urine collected from workers exposed to <5ppb (parts per billion). Information on workers' symptoms was collected through interviews. One nanomolar TDI robustly induced ATX release within 10min in vitro. A P2X7- and P2X4-dependent microvesicle formation was implicated in a rapid ATX release and a subsequent protein synthesis. Co-localization between purinergic receptors and ATX was documented by immunofluorescence and confocal microscopy. The release was modulated by monocyte chemoattractant protein-1 (MCP-1) and by extracellular ATP. In workers, we found a dose-response relationship between TDI exposure biomarkers in urine and LPA levels in plasma. Among symptomatic workers reporting "sneezing", the LPA levels were higher than among non-symptomatic workers. This is the first report indicating induction of the ATX-LPA axis by an environmental low-molecular-weight chemical, and our data suggest a role for the ATX-LPA axis in TDI toxicity.
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| 3. |
- Zheng, Huiyuan
(författare)
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Molecular function and targeting of β-arrestins in cancer
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the selection leading to cancer, cancer cells make use of the normal extracellular signaling to gain a growth advantage over normal cells. These signals are, in part, generated by plasma membrane receptors. G Protein Coupled Receptors (GPCRs) and Receptor Tyrosine Kinases (RTKs) are major transducer of signals across the plasma membrane. Each cell surface receptor family possesses unique structural characteristics and leads to specific signaling outcomes in the cell. However, there is extensive overlap in the signaling proteins and pathways used to produce these effects. Among them, β-arrestins, molecules previously considered to be associated exclusively with GPCRs are also involved in modulating signaling through a classical RTK, the insulin-like growth factor type 1 (IGF-1R). The overall objective of this thesis is to investigate the function and determine potential utility of the β-arrestins as molecular targets in cancer. This is based on the underlying hypothesis that the signaling complexes coordinated by β-arrestins and involving kinases and ubiquitin ligases contribute to tumorigenesis and the progression of cancer and could be targeted in therapies. Paper I identified the antimicrobial cathelicidin peptide LL-37 as a natural agonist for the IGF-1R. LL-37 binding to the receptor resulted in phosphorylation and ubiquitination of IGF-1R, and β-arrestin dependent signaling activation. This signaling activation was limited to the MAPK/ERK pathway without affecting the other main IGF-1R signaling pathway through PI3K/AKT, indicating that LL-37 may act as a β-arrestin biased agonist for the IGF-1R, sustaining the invasive phenotype. Paper II investigated the β-arrestin-IGF-1R binding mechanism and reveal the missing links that to functionally portray a prototypical RTK, the IGF-1R, as a GPCR: GRK dependent phosphorylation of IGF-1R serine residues as the underlying mechanism for β-arrestin binding. While highlighting the cross-talk between the IGF-1R and GPCR at the level of GRKs, this study identified the molecular basis of IGF-1R biased signaling to be dependent on β-arrestin/IGF-1R interaction controlled by GRKs. Paper III investigates the paradox of agonist-like IGF-1R downregulation following treatment with antagonist anti-IGF-1R antibodies. The results show that this process is governed by β-arrestin1 recruitment to the IGF-1R, initiating receptor ubiquitination and degradation. Yet, this β-arrestin1 recruitment to the IGF-1R initiates a wave of ERK signaling activation, demonstrated to have a protective role for the cancer cells. Paper IV reveals that β-arrestin1 mediated IGF-1R signalling is crucial for H-Ras induced transformation. The mechanism underlying this process is impaired intensity and spatial distribution of activated MAPK/ERK signalling in the absence of β-arrestin1. In conclusion, this thesis demonstrates that β-arrestins play a central role in IGF-1R function, controlling ubiquitination/degradation of the receptor, and receptor signaling. This study, focusing on β-arrestins as central molecules in modulation of the intracellular signaling, may provide new clues in the search for new molecular-designed treatments of cancer.
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