Dataset Information

CcpA-independent glucose regulation of lactate dehydrogenase 1 in Staphylococcus aureus.

ABSTRACT: Lactate Dehydrogenase 1 (Ldh1) is a key enzyme involved in Staphylococcus aureus NO·-resistance. Full ldh1-induction requires the presence of glucose, and mutants lacking the Carbon-Catabolite Protein (CcpA) exhibit decreased ldh1 transcription and diminished Ldh1 activity. The redox-regulator Rex represses ldh1 directly by binding to Rex-sites within the ldh1 promoter (P(ldh1)). In the absence of Rex, neither glucose nor CcpA affect ldh1 expression implying that glucose/CcpA-mediated activation requires Rex activity. Rex-mediated repression of ldh1 depends on cellular redox status and is maximal when NADH levels are low. However, compared to WT cells, the ?ccpA mutant exhibited impaired redox balance with relatively high NADH levels, yet ldh1 was still poorly expressed. Furthermore, CcpA did not drastically alter Rex transcript levels, nor did glucose or CcpA affect the expression of other Rex-regulated genes indicating that the glucose/CcpA effect is specific for P(ldh1). A putative catabolite response element (CRE) is located ?30 bp upstream of the promoter-distal Rex-binding site in P(ldh1). However, CcpA had no affinity for P(ldh1) in vitro and a genomic mutation of CRE upstream of P(ldh1) in S. aureus had no affect on Ldh1 expression in vivo. In contrast to WT, ?ccpA S. aureus preferentially consumes non-glycolytic carbon sources. However when grown in defined medium with glucose as the primary carbon source, ?ccpA mutants express high levels of Ldh1 compared to growth in media devoid of glucose. Thus, the actual consumption of glucose stimulates Ldh1 expression rather than direct CcpA interaction at P(ldh1).

SUBMITTER: Crooke AK

PROVIDER: S-EPMC3544828 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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CcpA-independent glucose regulation of lactate dehydrogenase 1 in Staphylococcus aureus.

Crooke Adrianne K AK Fuller James R JR Obrist Markus W MW Tomkovich Sarah E SE Vitko Nicholas P NP Richardson Anthony R AR

PloS one 20130114 1

Lactate Dehydrogenase 1 (Ldh1) is a key enzyme involved in Staphylococcus aureus NO·-resistance. Full ldh1-induction requires the presence of glucose, and mutants lacking the Carbon-Catabolite Protein (CcpA) exhibit decreased ldh1 transcription and diminished Ldh1 activity. The redox-regulator Rex represses ldh1 directly by binding to Rex-sites within the ldh1 promoter (P(ldh1)). In the absence of Rex, neither glucose nor CcpA affect ldh1 expression implying that glucose/CcpA-mediated activation ...[more]

PMID: 23342123

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Project description:The complex cross talk between metabolism and gene regulatory networks makes it difficult to untangle individual constituents and study their precise roles and interactions. To address this issue, we modularized the transcriptional regulatory network (TRN) of the Staphylococcus aureus USA300 strain by applying independent component analysis (ICA) to 385 RNA sequencing samples. We then combined the modular TRN model with a metabolic model to study the regulation of carbon and amino acid metabolism. Our analysis showed that regulation of central carbon metabolism by CcpA and amino acid biosynthesis by CodY are closely coordinated. In general, S. aureus increases the expression of CodY-regulated genes in the presence of preferred carbon sources such as glucose. This transcriptional coordination was corroborated by metabolic model simulations that also showed increased amino acid biosynthesis in the presence of glucose. Further, we found that CodY and CcpA cooperatively regulate the expression of ribosome hibernation-promoting factor, thus linking metabolic cues with translation. In line with this hypothesis, expression of CodY-regulated genes is tightly correlated with expression of genes encoding ribosomal proteins. Together, we propose a coarse-grained model where expression of S. aureus genes encoding enzymes that control carbon flux and nitrogen flux through the system is coregulated with expression of translation machinery to modularly control protein synthesis. While this work focuses on three key regulators, the full TRN model we present contains 76 total independently modulated sets of genes, each with the potential to uncover other complex regulatory structures and interactions. IMPORTANCE Staphylococcus aureus is a versatile pathogen with an expanding antibiotic resistance profile. The biology underlying its clinical success emerges from an interplay of many systems such as metabolism and gene regulatory networks. This work brings together models for these two systems to establish fundamental principles governing the regulation of S. aureus central metabolism and protein synthesis. Studies of these fundamental biological principles are often confined to model organisms such as Escherichia coli. However, expanding these models to pathogens can provide a framework from which complex and clinically important phenotypes such as virulence and antibiotic resistance can be better understood. Additionally, the expanded gene regulatory network model presented here can deconvolute the biology underlying other important phenotypes in this pathogen.

Dataset Information

CcpA-independent glucose regulation of lactate dehydrogenase 1 in Staphylococcus aureus.

Publications

CcpA-independent glucose regulation of lactate dehydrogenase 1 in Staphylococcus aureus.

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