Dataset Information

Microbial regulation of glucose metabolism and cell-cycle progression in mammalian colonocytes.

ABSTRACT: A prodigious number of microbes inhabit the human body, especially in the lumen of the gastrointestinal (GI) tract, yet our knowledge of how they regulate metabolic pathways within our cells is rather limited. To investigate the role of microbiota in host energy metabolism, we analyzed ATP levels and AMPK phosphorylation in tissues isolated from germfree and conventionally-raised C57BL/6 mice. These experiments demonstrated that microbiota are required for energy homeostasis in the proximal colon to a greater extent than other segments of the GI tract that also harbor high densities of bacteria. This tissue-specific effect is consistent with colonocytes utilizing bacterially-produced butyrate as their primary energy source, whereas most other cell types utilize glucose. However, it was surprising that glucose did not compensate for butyrate deficiency. We measured a 3.5-fold increase in glucose uptake in germfree colonocytes. However, (13)C-glucose metabolic-flux experiments and biochemical assays demonstrated that they shifted their glucose metabolism away from mitochondrial oxidation/CO(2) production and toward increased glycolysis/lactate production, which does not yield enough ATPs to compensate. The mechanism responsible for this metabolic shift is diminished pyruvate dehydrogenase (PDH) levels and activity. Consistent with perturbed PDH function, the addition of butyrate, but not glucose, to germfree colonocytes ex vivo stimulated oxidative metabolism. As a result of this energetic defect, germfree colonocytes exhibited a partial block in the G(1)-to-S-phase transition that was rescued by a butyrate-fortified diet. These data reveal a mechanism by which microbiota regulate glucose utilization to influence energy homeostasis and cell-cycle progression of mammalian host cells.

SUBMITTER: Donohoe DR

PROVIDER: S-EPMC3460890 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Microbial regulation of glucose metabolism and cell-cycle progression in mammalian colonocytes.

Donohoe Dallas R DR Wali Aminah A Brylawski Bruna P BP Bultman Scott J SJ

PloS one 20120928 9

A prodigious number of microbes inhabit the human body, especially in the lumen of the gastrointestinal (GI) tract, yet our knowledge of how they regulate metabolic pathways within our cells is rather limited. To investigate the role of microbiota in host energy metabolism, we analyzed ATP levels and AMPK phosphorylation in tissues isolated from germfree and conventionally-raised C57BL/6 mice. These experiments demonstrated that microbiota are required for energy homeostasis in the proximal colo ...[more]

PMID: 23029553

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Project description:In the model organism Caulobacter crescentus, a network of two-component systems involving the response regulators CtrA, DivK, and PleD coordinates cell cycle progression with differentiation. Active phosphorylated CtrA prevents chromosome replication in G1 cells while simultaneously regulating expression of genes required for morphogenesis and development. At the G1-S transition, phosphorylated DivK (DivK∼P) and PleD (PleD∼P) accumulate to indirectly inactivate CtrA, which triggers DNA replication initiation and concomitant cellular differentiation. The phosphatase PleC plays a pivotal role in this developmental program by keeping DivK and PleD phosphorylation levels low during G1, thereby preventing premature CtrA inactivation. Here, we describe CckN as a second phosphatase akin to PleC that dephosphorylates DivK∼P and PleD∼P in G1 cells. However, in contrast to PleC, no kinase activity was detected with CckN. The effects of CckN inactivation are largely masked by PleC but become evident when PleC and DivJ, the major kinase for DivK and PleD, are absent. Accordingly, mild overexpression of cckN restores most phenotypic defects of a pleC null mutant. We also show that CckN and PleC are proteolytically degraded in a ClpXP-dependent way before the onset of the S phase. Surprisingly, known ClpX adaptors are dispensable for PleC and CckN proteolysis, raising the possibility that as yet unidentified proteolytic adaptors are required for the degradation of both phosphatases. Since cckN expression is induced in stationary phase, depending on the stress alarmone (p)ppGpp, we propose that CckN acts as an auxiliary factor responding to environmental stimuli to modulate CtrA activity under suboptimal conditions.IMPORTANCE Two-component signal transduction systems are widely used by bacteria to adequately respond to environmental changes by adjusting cellular parameters, including the cell cycle. In Caulobacter crescentus, PleC acts as a phosphatase that indirectly protects the response regulator CtrA from premature inactivation during the G1 phase of the cell cycle. Here, we provide genetic and biochemical evidence that PleC is seconded by another phosphatase, CckN. The activity of PleC and CckN phosphatases is restricted to the G1 phase since both proteins are degraded by ClpXP protease before the G1-S transition. Degradation is independent of any known proteolytic adaptors and relies, in the case of CckN, on an unsuspected N-terminal degron. Our work illustrates a typical example of redundant functions between two-component proteins.

Dataset Information

Microbial regulation of glucose metabolism and cell-cycle progression in mammalian colonocytes.

Publications

Microbial regulation of glucose metabolism and cell-cycle progression in mammalian colonocytes.

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