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Metabolite changes signal genetic regulatory mechanisms for robust cell behavior.

ABSTRACT: UNLABELLED:Exploiting mechanisms of utilizing the sugar d-galactose in Escherichia coli as a model system, we explored the consequences of accumulation of critical intermediates of the d-galactose metabolic pathways by monitoring cell growth, metabolites, and transcript profiles. These studies revealed both metabolic network changes far from the d-galactose pathway and changes in the global gene regulatory network. The concentration change of a critical intermediate disturbs the equilibrium state, generating a ripple effect through several metabolic pathways that ends up signaling up- or downregulation of specific sets of genes in a programmed manner to cope with the imbalance. Such long-range effects on metabolites and genetic regulatory mechanisms not only may be a common feature in bacteria but very likely operate during cellular development and differentiation in higher organisms as well as in disease cells, like cancer cells. IMPORTANCE:Metabolite accumulation can create adverse intracellular conditions that are relieved by compensatory immediate changes of metabolite pools and later changes of transcript levels. It has been known that gene expression is normally regulated by added catabolic substrates (induction) or anabolic end products (repression). It is becoming apparent now that change in the concentration of metabolic intermediates also plays a critical role in genetic regulatory networks for metabolic homeostasis. Our study provides new insight into how metabolite pool changes transduce signals to global gene regulatory networks.

SUBMITTER: Lee SJ

PROVIDER: S-EPMC3903281 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Metabolite changes signal genetic regulatory mechanisms for robust cell behavior.

Lee Sang Jun SJ Trostel Andrei A Adhya Sankar S

mBio 20140128 1

<h4>Unlabelled</h4>Exploiting mechanisms of utilizing the sugar d-galactose in Escherichia coli as a model system, we explored the consequences of accumulation of critical intermediates of the d-galactose metabolic pathways by monitoring cell growth, metabolites, and transcript profiles. These studies revealed both metabolic network changes far from the d-galactose pathway and changes in the global gene regulatory network. The concentration change of a critical intermediate disturbs the equilibr ...[more]

PMID: 24473130

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Project description:Regulatory T cells (Tregs) are immunosuppressive cells of the immune system that control autoimmune reactivity. Tregs also respond during immune reactions to infectious agents in order to limit immunopathological damage from potent effectors such as CD8+ cytolytic T lymphocytes. We have used the Friend virus (FV) model of retroviral infection in mice to investigate how viral infections induce Tregs. During acute FV infection, there is significant activation and expansion of thymus-derived (natural) Tregs that suppress virus-specific CD8+ T cell responses. Unlike conventional T cells, the responding Tregs are not virus specific, so the mechanisms that induce their expansion are of great interest. We now show that B cells provide essential signals for Treg expansion during FV infection. Treg responses are greatly diminished in B cell-deficient mice but can be restored by adoptive transfers of B cells at the time of infection. The feeble Treg responses in B cell-deficient mice are associated with enhanced virus-specific CD8+ T cell responses and accelerated virus control during the first 2 weeks of infection. In vitro experiments demonstrated that B cells promote Treg activation and proliferation through a glucocorticoid-induced receptor superfamily member 18 (GITR) ligand-dependent mechanism. Thus, B cells play paradoxically opposing roles during FV infection. They provide proliferative signals to immunsosuppressive Tregs, which slows early virus control, and they also produce virus-specific antibodies, which are essential for long-term virus control.IMPORTANCE When infectious agents invade a host, numerous immunological mechanisms are deployed to limit their replication, neutralize their spread, and destroy the host cells harboring the infection. Since immune responses also have a strong capacity to damage host cells and tissues, their magnitude, potency, and duration are under regulatory control. Regulatory T cells are an important component of this control, and the mechanisms that induce them to respond and exert immunosuppressive regulation are of great interest. In the current report, we show that B cells, the cells responsible for making pathogen-specific antibodies, are also involved in promoting the expansion of regulatory T cells during a retroviral infection. In vitro studies demonstrated that they do so via stimulation of the Tregs through interactions between cell surface molecules: GITR interactions with its ligand (GITRL) on B cells and GITR on regulatory T cells. These findings point the way toward therapeutics to better treat infections and autoimmune diseases.

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Metabolite changes signal genetic regulatory mechanisms for robust cell behavior.

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Metabolite changes signal genetic regulatory mechanisms for robust cell behavior.

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