Themis2/ICB1 Is a Signaling Scaffold That Selectively Regulates Macrophage Toll-Like Receptor Signaling and Cytokine Production

Background

Thymocyte expressed molecule involved in selection 1 (Themis1, SwissProt accession number {"type":"entrez-protein","attrs":{"text":"Q8BGW0","term_id":"81896053","term_text":"Q8BGW0"}}Q8BGW0) is the recently characterised founder member of a novel family of proteins. A second member of this family, Themis2 ({"type":"entrez-protein","attrs":{"text":"Q91YX0","term_id":"73920022","term_text":"Q91YX0"}}Q91YX0), also known as ICB1 (Induced on contact with basement membrane 1), remains unreported at the protein level despite microarray and EST databases reporting Themis2 mRNA expression in B cells and macrophages.

Methodology/Principal Findings

Here we characterise Themis2 protein for the first time and show that it acts as a macrophage signalling scaffold, exerting a receptor-, mediator- and signalling pathway-specific effect on TLR responses in RAW 264.7 macrophages. Themis2 over-expression enhanced the LPS-induced production of TNF but not IL-6 or Cox-2, nor TNF production induced by ligands for TLR2 (PAM3) or TLR3 (poly I∶C). Moreover, LPS-induced activation of the MAP kinases ERK and p38 was enhanced in cells over-expressing Themis2 whereas the activation of JNK, IRF3 or NF-κB p65, was unaffected. Depletion of Themis2 protein by RNA inteference inhibited LPS-induced TNF production in primary human macrophages demonstrating a requirement for Themis2 in this event. Themis2 was inducibly tyrosine phosphorylated upon LPS challenge and interacted with Lyn kinase ({"type":"entrez-protein","attrs":{"text":"P25911","term_id":"2507208","term_text":"P25911"}}P25911), the Rho guanine nucleotide exchange factor, Vav ({"type":"entrez-protein","attrs":{"text":"P27870","term_id":"137483","term_text":"P27870"}}P27870), and the adaptor protein Grb2 ({"type":"entrez-protein","attrs":{"text":"Q60631","term_id":"2498425","term_text":"Q60631"}}Q60631). Mutation of either tyrosine 660 or a proline-rich sequence (PPPRPPK) simultaneously interrupted this complex and reduced by approximately 50% the capacity of Themis2 to promote LPS-induced TNF production. Finally, Themis2 protein expression was induced during macrophage development from murine bone marrow precursors and was regulated by inflammatory stimuli both in vitro and in vivo.

Conclusions/Significance

We hypothesise that Themis2 may constitute a novel, physiological control point in macrophage inflammatory responses.     

The influence of non‐climate predictors at local and landscape resolutions depends on the autecology of the species

Species distribution models have come under criticism for being too simplistic for making robust future forecasts, partly because they assume that climate is the main determinant of geographical range at large spatial extents and coarse resolutions, with non‐climate predictors being important only at finer scales. We suggest that this paradigm might be obscured by species movement patterns. To explore this we used contrasting kangaroo (family Macropodidae) case studies: two species with relatively small, stable home ranges (Macropus giganteus and M. robustus) and three species with more extensive, adaptive ranging behaviour (M. antilopinus, M. fuliginosus and M. rufus). We predicted that non‐climate predictors will be most influential to model fit and predictive performance at local spatial resolution for the former species and at landscape resolution for the latter species. We compared residuals autocovariate – boosted regression tree (RAC‐BRT) model statistics with and without species‐specific non‐climate predictors (habitat, soil, fire, water and topography), at local‐ and landscape‐level spatial resolutions (5 and 50 km). As predicted, the influence of non‐climate predictors on model fit and predictive performance (compared with climate‐only models) was greater at 50 compared with 5 km resolution for M. rufus and M. fuliginosus and the opposite trend was observed for M. giganteus. The results for M. robustus and M. antilopinus were inconclusive. Also notable was the difference in inter‐scale importance of climate predictors in the presence of non‐climate predictors. In conclusion, differences in autecology, particularly relating to space use, may contribute to the importance of non‐climate predictors at a given scale, not model scale per se. Further exploration of this concept across a range of species is encouraged and findings may contribute to more effective conservation and management of species at ecologically meaningful scales.     

The Restoration of Phytophagous Beetles in Species‐Rich Chalk Grasslands

This study focuses on the restoration of chalk grasslands over a 6‐year period and tests the efficacy of two management practices, hay spreading and soil disturbance, in promoting this process for phytophagous beetles. Restoration success for the beetles, measured as similarity to target species–rich chalk grassland, was not found to be influenced by either management practice. In contrast, restoration success for the plants did increase in response to hay spreading management. Although the presence of suitable host plants was considered to dictate the earliest point at which phytophagous beetles could successfully colonized, few beetle species colonized as soon as their host plants became established. Morphological characteristics and feeding habits of 27 phytophagous beetle species were therefore tested to identify factors that limited their colonization and persistence. The lag time between host plant establishment and colonization was greatest for flightless beetles. Beetles with foliage‐feeding larvae both colonized at slower rates than seed‐, stem‐, or root‐feeding species and persisted within the swards for shorter periods. Although the use of hay spreading may benefit plant communities during chalk grassland restoration, it did not directly benefit phytophagous beetles. Without techniques for overcoming colonization limitation for invertebrate taxa, short‐term success of restoration may be limited to the plants only.     

Posttranslational regulation of tristetraprolin subcellular localization and protein stability by p38 mitogen-activated protein kinase and extracellular signal-regulated kinase pathways

The p38 mitogen-activated protein kinase (MAPK) signaling pathway, acting through the downstream kinase MK2, regulates the stability of many proinflammatory mRNAs that contain adenosine/uridine-rich elements (AREs). It is thought to do this by modulating the expression or activity of ARE-binding proteins that regulate mRNA turnover. MK2 phosphorylates the ARE-binding and mRNA-destabilizing protein tristetraprolin (TTP) at serines 52 and 178. Here we show that the p38 MAPK pathway regulates the subcellular localization and stability of TTP protein. A p38 MAPK inhibitor causes rapid dephosphorylation of TTP, relocalization from the cytoplasm to the nucleus, and degradation by the 20S/26S proteasome. Hence, continuous activity of the p38 MAPK pathway is required to maintain the phosphorylation status, cytoplasmic localization, and stability of TTP protein. The regulation of both subcellular localization and protein stability is dependent on MK2 and on the integrity of serines 52 and 178. Furthermore, the extracellular signal-regulated kinase (ERK) pathway synergizes with the p38 MAPK pathway to regulate both stability and localization of TTP. This effect is independent of kinases that are known to be synergistically activated by ERK and p38 MAPK. We present a model for the actions of TTP and the p38 MAPK pathway during distinct phases of the inflammatory response.     

Regional localisations and linkage relationships of seven RFLPs and myotonic dystrophy on chromosome 19

Summary We have studied the genetic linkage relationships of seven DNA polymorphisms on chromosome 19, with each other and with the myotonic dystrophy locus. The DNA sequences were localised to various regions of the chromosome using translocations in somatic cell hybrids. These results provide the basis for a linkage map of most of chromosome 19, and suggest that the myotonic dystrophy locus is close to the centromere.