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Identification and characterization of phosphodiesterases that specifically degrade 3'3'-cyclic GMP-AMP.

ABSTRACT: Cyclic dinucleotides act as intracellular second messengers, modulating a variety of cellular activities including innate immune activation. Although phosphodiesterases (PDEs) hydrolyzing c-di-GMP and c-di-AMP have been identified, no PDEs for cGAMPs have been reported. Here we identified the first three cGAMP-specific PDEs in V. cholerae (herein designated as V-cGAP1/2/3). V-cGAPs are HD-GYP domain-containing proteins and specifically break 3'3'-cGAMP, but not other forms of cGAMP. 3'3'-cGAMP is first linearized by all three V-cGAPs to produce 5'-pApG, which is further hydrolyzed into 5'-ApG by V-cGAP1. In this two-step reaction, V-cGAP1 functions as both a PDE and a 5'-nucleotidase. In vivo experiments demonstrated that V-cGAPs play non-redundant roles in cGAMP degradation. The high specificity of V-cGAPs on 3'3'-cGAMP suggests the existence of specific PDEs for other cGAMPs, including 2'3'-cGAMP in mammalian cells. The absolute requirement of the GYP motif for 3'3'-cGAMP degradation suggests that HD domain-containing PDEs in eukaryotes are probably unable to hydrolyze cGAMPs. The fact that all V-cGAPs attack 3'3'-cGAMP on one specific phosphodiester bond suggests that PDEs for other cGAMPs would utilize a similar strategy. These results will provide valuable information for identification and characterization of mammalian 2'3'-cGAMP-specific PDEs in future studies.

SUBMITTER: Gao J

PROVIDER: S-EPMC4423081 | biostudies-other | 2015 May

REPOSITORIES: biostudies-other

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Identification and characterization of phosphodiesterases that specifically degrade 3'3'-cyclic GMP-AMP.

Gao Juyi J Tao Jianli J Liang Weili W Zhao Meng M Du Xiaoxia X Cui Shan S Duan Haifeng H Kan Biao B Su Xiaodong X Jiang Zhengfan Z

Cell research 20150403 5

Cyclic dinucleotides act as intracellular second messengers, modulating a variety of cellular activities including innate immune activation. Although phosphodiesterases (PDEs) hydrolyzing c-di-GMP and c-di-AMP have been identified, no PDEs for cGAMPs have been reported. Here we identified the first three cGAMP-specific PDEs in V. cholerae (herein designated as V-cGAP1/2/3). V-cGAPs are HD-GYP domain-containing proteins and specifically break 3'3'-cGAMP, but not other forms of cGAMP. 3'3'-cGAMP i ...[more]

PMID: 25837739

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Project description:Intracellular levels of the bacterial second messenger cyclic di-GMP (c-di-GMP) are controlled by antagonistic activities of diguanylate cyclases and phosphodiesterases. The phosphodiesterase PdeH was identified as a key regulator of motility in Escherichia coli, while deletions of any of the other 12 genes encoding potential phosphodiesterases did not interfere with motility. To analyze the roles of E. coli phosphodiesterases, we demonstrated that most of these proteins are expressed under laboratory conditions. We next isolated suppressor mutations in six phosphodiesterase genes, which reinstate motility in the absence of PdeH by reducing cellular levels of c-di-GMP. Expression of all mutant alleles also led to a reduction of biofilm formation. Thus, all of these proteins are bona fide phosphodiesterases that are capable of interfering with different c-di-GMP-responsive output systems by affecting the global c-di-GMP pool. This argues that E. coli possesses several phosphodiesterases that are inactive under laboratory conditions because they lack appropriate input signals. Finally, one of these phosphodiesterases, PdeL, was studied in more detail. We demonstrated that this protein acts as a transcription factor to control its own expression. Motile suppressor alleles led to a strong increase of PdeL activity and elevated pdeL transcription, suggesting that enzymatic activity and transcriptional control are coupled. In agreement with this, we showed that overall cellular levels of c-di-GMP control pdeL transcription and that this control depends on PdeL itself. We thus propose that PdeL acts both as an enzyme and as a c-di-GMP sensor to couple transcriptional activity to the c-di-GMP status of the cell.Most bacteria possess multiple diguanylate cyclases and phosphodiesterases. Genetic studies have proposed that these enzymes show signaling specificity by contributing to distinct cellular processes without much cross talk. Thus, spatial separation of individual c-di-GMP signaling units was postulated. However, since most cyclases and phosphodiesterases harbor N-terminal signal input domains, it is equally possible that most of these enzymes lack their activating signals under laboratory conditions, thereby simulating signaling specificity on a genetic level. We demonstrate that a subset of E. coli phosphodiesterases can be activated genetically to affect the global c-di-GMP pool and thus influence different c-di-GMP-dependent processes. Although this does not exclude spatial confinement of individual phosphodiesterases, this study emphasizes the importance of environmental signals for activation of phosphodiesterases.

Dataset Information

Identification and characterization of phosphodiesterases that specifically degrade 3'3'-cyclic GMP-AMP.

Publications

Identification and characterization of phosphodiesterases that specifically degrade 3'3'-cyclic GMP-AMP.

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