Project description:The second messenger, cyclic-AMP (cAMP) is conserved across all taxa of life. It is involved in propagating the signal from environmental stimuli and converting it into a response. In bacteria such as M. tuberculosis (Mtb), P. aeruginosa, V. cholerae and B. pertussis, cAMP has been implicated in virulence, regulation of metabolism and gene expression. Cyclic AMP signalling in mycobacteria is especially complex – with 16 enzymes that produce cAMP in Mtb alone. By discovery of a novel, actinobacteria conserved enzyme that degrades cAMP, we have developed a tool to modulate cAMP levels in mycobacteria. By using a combination of metabolomics, bioenergetics and time-to-kill assays, we show that when this enzyme is overexpressed in the model organism M. smegmatis, there is a 3.3 -fold decrease in intracellular cAMP levels. This was concomitant with altered cell envelope permeability, compromised bioenergetics and most importantly, led to a decrease in the tolerance to various frontline antimicrobials. Taken together, this work provides clear evidence that cAMP is involved in antimicrobial tolerance in mycobacteria and that this may represent a promising new target for antimicrobial development.
Project description:We have previously reported that Mycobacterium tuberculosis Rv2837c (cnpB) encodes a phosphodiesterase that specifically cleaves cyclic di-AMP (c-di-AMP) into AMP. Deletion of cnpB results in significant virulence attenuation in a mouse pulmonary infection model, which is very likely due to the significantly elevated c-di-AMP levels as overexpression of Mtb diadenylate cyclase, disA, also leads to a similar outcome. An earlier study also demonstrated that CnpB functions similarly to E. coli oligoribonuclease (Orn) that hydrolyzes 2-5-mer nanoRNAs (short oligonucleotides of five residues or shorter in length) except that CnpB prefers 2-mer nanoRNA as a substrate. Additionally, a recent report showed that CnpB also degrades cyclic di-GMP (c-di-GMP), although we demonstrated that CnpB prefers c-di-AMP to c-di-GMP according to an in vitro enzymatic kinetics analysis In this study, we initially attempted to determine c-di-AMP-mediated gene regulation in Mtb by comparing the expression profiles between WT and ∆cnpB using RNA-Seq. We found that the CRISPR-Cas system of M. tuberculosis was highly upregulated by deletion of cnpB.
Project description:Analysis of MDA-MB-231 breast tumor cell from knocking-down phosphodiesterase 3A (PDE3A), a cyclic nucleotide phosphodiesterase. Results provide insight into the role of PDE3A in breast tumor progression and metastasis.
Project description:The development of an effective vaccine to protect against HIV acquisition will be greatly bolstered by in-depth understanding of the innate and adaptive responses to the virus. We report here that the efficacy of DNA/ALVAC/gp120/alum vaccines, based on V2-specific antibodies mediating apoptosis of infected cells (V2-ADCC), is complemented by efferocytosis, a cyclic AMP (cAMP)-dependent antiphlogistic engulfment of apoptotic cells by CD14+ monocytes. Central to vaccine efficacy is the engagement of the CCR2+/CCL2 axis and tolerogenic dendritic cells producing IL-10 (DC-10). Durable epigenetic reprogramming in CD14+ cells of the cyclic AMP/CREB pathway and increased levels of miRNA-139-5p, a negative regulator of expression of the cAMP-specific phosphodiesterase PDE4D, in extracellular vesicles correlated with vaccine efficacy. These data posit that efferocytosis, through the prompt and effective removal of apoptotic infected cells, contributes to vaccine efficacy by decreasing inflammation and maintaining tissue homeostasis.
Project description:Streptococcus agalactiae is among the few pathogens that have not developed resistance to ß-lactam antibiotics despite decades of clinical use. The molecular basis of this long-lasting susceptibility has not been investigated, and it is uncertain whether specific mechanisms constraint the emergence of resistance. In this study, we first report a conserved role of the signaling nucleotide cyclic-di-AMP in the sensitivity of S. agalactiae to ß-lactam. Specifically, we demonstrate that inactivation of the phosphodiesterase GdpP confers ß-lactam tolerance. Characterizing the signaling pathway revealed an antagonistic regulation by the transcriptional factor BusR, which is activated by c-di-AMP and negatively regulates ß-lactam susceptibility. Furthermore, we show that simultaneous inhibition of osmolyte transporters activity and transcription by c-di-AMP has an additive effect, sustaining ß-lactam tolerance. Finally, transposon mutagenesis for ß-lactam reduced susceptibility reveals a convergent pattern of mutations, including in the KhpAB small RNA chaperone and the protein S immunomodulator. Overall, our findings suggest mechanisms that may foster antibiotic resistance in S. agalactiae and demonstrate that c-di-AMP acts as a turgor pressure rheostat, coordinating an integrated response to cell wall weakening due to ß-lactam activity.
Project description:The impact of 2',3'-cyclic nucleotide monophosphates (2',3'-cNMPs) on global gene expression in S. Typhimurium was investigated by heterologous expression of a 2',3'-cyclic nucleotide phosphodiesterase (CNPase), which reduces intracellular 2',3'-cNMP levels.
Project description:The impact of 2',3'-cyclic nucleotide monophosphates (2',3'-cNMPs) on global gene expression in E. coli was investigated by heterologous expression of a 2',3'-cyclic nucleotide phosphodiesterase (CNPase), which reduces intracellular 2',3'-cNMP levels.
Project description:c-di-GMP and c-di-AMP are important conserved second messenger in bacteria, they play a critical role in a wide range of cellular processes, such as motility, virulence, biofilm formation, cell-cycle progression and cell development, but there are only two c-di-GMP receptors and one c-di-AMP receptors were identified in mycobacteria so far, to identify more c-di-GMP and c-di-AMP receptors we compare the protein expression level of c-di-GMP or c-di-AMP synthesis enzyme overexpression strain with the wild type Mycobacterium smegmatis.
Project description:The collective movement of African trypanosomes on semi-solid surfaces, known as social motility, is presumed to be due to migration factors and repellents released by the parasites. Here we show that procyclic (insect midgut) forms acidify their environment as a consequence of glucose metabolism, generating pH gradients by diffusion. Early and late procyclic forms exhibit self-organising properties on agarose plates. While early procyclic forms are repelled by acid and migrate outwards, late procyclic forms remain at the inoculation site. Furthermore, trypanosomes respond to exogenously formed pH gradients, with both early and late procyclic forms being attracted to alkali. pH taxis is mediated by multiple cyclic AMP effectors: deletion of one copy of adenylate cyclase ACP5, or both copies of the cyclic AMP response protein CARP3, abrogates the response to acid, while deletion of phosphodiesterase PDEB1 completely abolishes pH taxis. The ability to sense pH is biologically relevant as trypanosomes experience large changes as they migrate through their tsetse host. Supporting this, a CARP3 null mutant is severely compromised in its ability to establish infections in flies. Based on these findings, we propose that the expanded family of adenylate cyclases in trypanosomes might govern other chemotactic responses in their two hosts.