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Expression of cyclic GMP-inhibited phosphodiesterases 3A and 3B (PDE3A and PDE3B) in rat tissues: differential subcellular localization and regulated expression by cyclic AMP.

ABSTRACT: A combination of pharmacological, molecular biological and biochemical approaches were used to investigate the differential expression of two cyclic GMP-inhibited cyclic nucleotide phosphodiesterase genes (PDE3A and PDE3B) in the rat. RT PCR using PDE3A- or PDE3B-specific oligonucleotide primers allowed amplification of products encoding PDE3A (508 bp) or PDE3B (499 bp) sequences from several rat tissues (heart, aorta, liver, kidney and epididymal fat), from primary cultures of aortic vascular smooth muscle cells (VSMC) as well as from an SV40 large T-antigen immortalized aortic VSMC line. Immunoblotting experiments with PDE3-selective antisera allowed the detection of both PDE3A and PDE3B immunoreactive proteins in several rat tissues, including tissues of the cardiovascular system, in primary cultures of aortic VSMC and in an SV40 large T-antigen immortalized aortic VSMC line. In all cases, PDE3A was expressed as a 120 kDa protein which was only detected in the cytosolic fraction. PDE3B was expressed as a 135 kDa protein and its expression was limited to the particulate fraction of all tissues and cells studied. Prolonged incubation of cultured aortic VSMC with agents that increase VSMC cyclic AMP (forskolin or 8-bromo-cyclic AMP) produced marked time-dependent increases in PDE3 activity which correlated with increases in PDE3A and PDE3B RT PCR signals and a marked increase in particulate PDE3 activity and PDE3B protein. The physiological, pharmacological and biochemical implications of these findings are discussed based on previous reports of the effects of PDE3 inhibitors in the cardiovascular system and the relevance of our findings are presented in the context of the development of PDE3A and/or PDE3B-selective pharmacological agents.

SUBMITTER: Liu H

PROVIDER: S-EPMC1565736 | biostudies-other | 1998 Dec

REPOSITORIES: biostudies-other

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Expression of cyclic GMP-inhibited phosphodiesterases 3A and 3B (PDE3A and PDE3B) in rat tissues: differential subcellular localization and regulated expression by cyclic AMP.

Liu H H Maurice D H DH

British journal of pharmacology 19981201 7

A combination of pharmacological, molecular biological and biochemical approaches were used to investigate the differential expression of two cyclic GMP-inhibited cyclic nucleotide phosphodiesterase genes (PDE3A and PDE3B) in the rat. RT PCR using PDE3A- or PDE3B-specific oligonucleotide primers allowed amplification of products encoding PDE3A (508 bp) or PDE3B (499 bp) sequences from several rat tissues (heart, aorta, liver, kidney and epididymal fat), from primary cultures of aortic vascular s ...[more]

PMID: 9884079

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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.

Project description:Klebsiella pneumoniae is the predominant pathogen isolated from liver abscesses of diabetic patients in Asian countries. However, the effects of elevated blood glucose levels on the virulence of this pathogen remain largely unknown. Type 3 fimbriae, encoded by the mrkABCDF genes, are important virulence factors in K. pneumoniae pathogenesis. In this study, the effects of exogenous glucose and the intracellular cyclic AMP (cAMP) signaling pathway on type 3 fimbriae expression regulation were investigated. The production of MrkA, the major subunit of type 3 fimbriae, was increased in glucose-rich medium, whereas cAMP supplementation reversed the effect. MrkA production was markedly increased by cyaA or crp deletion, but slightly decreased by cpdA deletion. In addition, the mRNA levels of mrkABCDF genes and the activity of PmrkA were increased in Δcrp strain, as well as the mRNA levels of mrkHIJ genes that encode cyclic di-GMP (c-di-GMP)-related regulatory proteins that influence type 3 fimbriae expression. Moreover, the activities of PmrkHI and PmrkJ were decreased in ΔlacZΔcrp strain. These results indicate that CRP-cAMP down-regulates mrkABCDF and mrkHIJ at the transcriptional level. Further deletion of mrkH or mrkI in Δcrp strain diminished the production of MrkA, indicating that MrkH and MrkI are required for the CRP regulation of type 3 fimbriae expression. Furthermore, the high activity of PmrkHI in the ΔlacZΔcrp strain was diminished in ΔlacZΔcrpΔmrkHI, but increased in the ΔlacZΔcrpΔmrkJ strain. Deletion of crp increased the intracellular c-di-GMP concentration and reduced the phosphodiesterase activity. Moreover, we found that the mRNA levels of multiple genes related to c-di-GMP metabolism were altered in Δcrp strain. These indicate that CRP regulates type 3 fimbriae expression indirectly via the c-di-GMP signaling pathway. In conclusion, we found evidence of a coordinated regulation of type 3 fimbriae expression by the CRP-cAMP and c-di-GMP signaling pathways in K. pneumoniae.

Dataset Information

Expression of cyclic GMP-inhibited phosphodiesterases 3A and 3B (PDE3A and PDE3B) in rat tissues: differential subcellular localization and regulated expression by cyclic AMP.

Publications

Expression of cyclic GMP-inhibited phosphodiesterases 3A and 3B (PDE3A and PDE3B) in rat tissues: differential subcellular localization and regulated expression by cyclic AMP.

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