Proteomic and Physiological Responses of Kineococcus radiotolerans to Copper

Copper is a highly reactive, toxic metal; consequently, transport of this metal within the cell is tightly regulated. Intriguingly, the actinobacterium Kineococcus radiotolerans has been shown to not only accumulate soluble copper to high levels within the cytoplasm, but the phenotype also correlated with enhanced cell growth during chronic exposure to ionizing radiation. This study offers a first glimpse into the physiological and proteomic responses of K. radiotolerans to copper at increasing concentration and distinct growth phases. Aerobic growth rates and biomass yields were similar over a range of Cu(II) concentrations (0–1.5 mM) in complex medium. Copper uptake coincided with active cell growth and intracellular accumulation was positively correlated with Cu(II) concentration in the growth medium (R2 = 0.7). Approximately 40% of protein coding ORFs on the K. radiotolerans genome were differentially expressed in response to the copper treatments imposed. Copper accumulation coincided with increased abundance of proteins involved in oxidative stress and defense, DNA stabilization and repair, and protein turnover. Interestingly, the specific activity of superoxide dismutase was repressed by low to moderate concentrations of copper during exponential growth, and activity was unresponsive to perturbation with paraquot. The biochemical response pathways invoked by sub-lethal copper concentrations are exceptionally complex; though integral cellular functions are preserved, in part, through the coordination of defense enzymes, chaperones, antioxidants and protective osmolytes that likely help maintain cellular redox. This study extends our understanding of the ecology and physiology of this unique actinobacterium that could potentially inspire new biotechnologies in metal recovery and sequestration, and environmental restoration

Lipopolysaccharide-induced NF-κB nuclear translocation is primarily dependent on MyD88, but TNFα\alpha expression requires TRIF and MyD88

TLR4 signalling through the MyD88 and TRIF-dependent pathways initiates translocation of the transcription factor NF-κB into the nucleus. In cell population studies using mathematical modeling and functional analyses, Cheng et al. suggested that LPS-driven activation of MyD88, in the absence of TRIF, impairs NF-κB translocation. We tested the model proposed by Cheng et al. using real-time single cell analysis in macrophages expressing EGFP-tagged p65 and a TNF$\alpha$ promoter-driven mCherry. Following LPS stimulation, cells lacking TRIF show a pattern of NF-κB dynamics that is unaltered from wild-type cells, but activation of the TNF$\alpha$ promoter is impaired. In macrophages lacking MyD88, there is minimal NF-κB translocation to the nucleus in response to LPS stimulation, and there is no activation of the TNF$\alpha$ promoter. These findings confirm that signalling through MyD88 is the primary driver for LPS-dependent NF-κB translocation to the nucleus. The pattern of NF-κB dynamics in TRIF-deficient cells does not, however, directly reflect the kinetics of TNF$\alpha$ promoter activation, supporting the concept that TRIF-dependent signalling plays an important role in the transcription of this cytokine.J.S. is supported by the Cambridge Commonwealth, European and International Trust. CEB was supported by a BBSRC fellowship (BB/H021930/1) and a Wellcome Trust Investigator award (WT108045AIA). E.C. and P.C. acknowledge EU-ITN Transpol and EU-ERC Hydrosync. I.D.C.F. is supported by the intramural Research Program of the National Institute of Allergy and Infectious Diseases