Single-Cell and Population NF-κB Dynamic Responses Depend on Lipopolysaccharide Preparation

Gutschow, Miriam V.; Hughey, Jacob J.; Ruggero, Nicholas A.; Bajar, Bryce T.; Valle, Sean D.; Covert, Markus W.

doi:10.1371/journal.pone.0053222

Cited by 18 publications

(26 citation statements)

References 24 publications

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“…Different types of LPS have been shown to produce dramatically different host responses, with diversity in LPS structures having been described between bacterial populations exposed to different environments (Paciello et al, 2013), different bacterial mutants (Guo et al, 1997), and different LPS variants resulting from different isolation procedures (Gutschow et al, 2013). We now show that heterogeneity also exists within a single population of wild-type bacteria.…”

Section: Discussionmentioning

confidence: 99%

Pathogen Cell-to-Cell Variability Drives Heterogeneity in Host Immune Responses

Avraham

Haseley

Brown

et al. 2015

Cell

280

263

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Summary Encounters between immune cells and invading bacteria ultimately determine the course of infection. These interactions are usually measured in populations of cells, masking cell-to-cell variation that may be important for infection outcome. To characterize gene expression variation that underlies distinct infection outcomes, we developed an experimental system that combines single-cell RNA-seq with fluorescent markers, monitoring infection phenotypes. Probing the responses of individual macrophages to invading Salmonella, we find that variation between individual infected host cells is determined by the heterogeneous activity of bacterial factors in individual infecting bacteria. We illustrate how variable PhoPQ activity in the population of invading bacteria drives variable host Type I IFN responses by modifying LPS in a subset of bacteria. This work demonstrates a causative link between host and bacterial variability, with cell-to-cell variation between different bacteria being sufficient to drive radically different host immune responses. This co-variation has implications for host-pathogen dynamics in vivo.

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Section: Discussionmentioning

confidence: 99%

Pathogen Cell-to-Cell Variability Drives Heterogeneity in Host Immune Responses

Avraham

Haseley

Brown

et al. 2015

Cell

280

263

View full text Add to dashboard Cite

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“…7). It will be interesting in the future to examine which features of the signaling dynamics are shared across different sources of LPS (32) and other TLR ligands. Analog information processing and feedback dominance switching may also be important in other cell types that require accurate single-cell-level decision-making to mount functional responses to specific signals.…”

Section: Discussionmentioning

confidence: 99%

Switching of the Relative Dominance Between Feedback Mechanisms in Lipopolysaccharide-Induced NF-κB Signaling

et al. 2014

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A fundamental goal in biology is to gain a quantitative understanding of how appropriate cell responses are achieved amid conflicting signals that work in parallel. Here, through live, single-cell imaging, we monitored both the dynamics of nuclear factor κB (NF-κB) signaling and inflammatory cytokine transcription in macrophages exposed to the bacterial product lipopolysaccharide (LPS). Our analysis revealed a previously uncharacterized positive feedback loop involving induction of the expression of Rela [which encodes the RelA (p65) subunit of NF-κB], which rewires the regulatory network when cells were stimulated with LPS above a distinct concentration. Paradoxically, this rewiring of NF-κB signaling in macrophages (a myeloid cell type) required the transcription factor Ikaros, which promotes the development of lymphoid cells. Mathematical modeling and experimental validation showed that the RelA positive feedback overcame existing negative feedback loops and enabled cells to discriminate between different concentrations of LPS so as to mount an effective innate immune response only at higher concentrations. We suggest that this switching in the relative dominance of feedback loops (“feedback dominance switching”) may be a general mechanism whereby immune cells integrate opposing feedback on a key transcriptional regulator and set a response threshold for the host.

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“…Hao and Baltimore found that TNFα mRNA degradation is several-fold lower when TNFα is produced in response to LPS when compared to TNFα stimulation [67]. This explains why the LPS stimulation leads to the massive secretion of TNFα, which in turn may trigger autocrine signaling, leading to prolonged oscillations of NF-κB, observed recently in a fraction of LPS-stimulated cells [68].…”

Section: Introductionmentioning

confidence: 87%

Spontaneous NF-κB Activation by Autocrine TNFα Signaling: A Computational Analysis

et al. 2013

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NF-κB is a key transcription factor that regulates innate immune response. Its activity is tightly controlled by numerous feedback loops, including two negative loops mediated by NF-κB inducible inhibitors, IκBα and A20, which assure oscillatory responses, and by positive feedback loops arising due to the paracrine and autocrine regulation via TNFα, IL-1 and other cytokines. We study the NF-κB system of interlinked negative and positive feedback loops, combining bifurcation analysis of the deterministic approximation with stochastic numerical modeling. Positive feedback assures the existence of limit cycle oscillations in unstimulated wild-type cells and introduces bistability in A20-deficient cells. We demonstrated that cells of significant autocrine potential, i.e., cells characterized by high secretion of TNFα and its receptor TNFR1, may exhibit sustained cytoplasmic–nuclear NF-κB oscillations which start spontaneously due to stochastic fluctuations. In A20-deficient cells even a small TNFα expression rate qualitatively influences system kinetics, leading to long-lasting NF-κB activation in response to a short-pulsed TNFα stimulation. As a consequence, cells with impaired A20 expression or increased TNFα secretion rate are expected to have elevated NF-κB activity even in the absence of stimulation. This may lead to chronic inflammation and promote cancer due to the persistent activation of antiapoptotic genes induced by NF-κB. There is growing evidence that A20 mutations correlate with several types of lymphomas and elevated TNFα secretion is characteristic of many cancers. Interestingly, A20 loss or dysfunction also leaves the organism vulnerable to septic shock and massive apoptosis triggered by the uncontrolled TNFα secretion, which at high levels overcomes the antiapoptotic action of NF-κB. It is thus tempting to speculate that some cancers of deregulated NF-κB signaling may be prone to the pathogen-induced apoptosis.

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Single-Cell and Population NF-κB Dynamic Responses Depend on Lipopolysaccharide Preparation

Cited by 18 publications

References 24 publications

Pathogen Cell-to-Cell Variability Drives Heterogeneity in Host Immune Responses

Pathogen Cell-to-Cell Variability Drives Heterogeneity in Host Immune Responses

Switching of the Relative Dominance Between Feedback Mechanisms in Lipopolysaccharide-Induced NF-κB Signaling

Spontaneous NF-κB Activation by Autocrine TNFα Signaling: A Computational Analysis

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