Project description:Analyses of gene expression profiles in evolutionarily diverse organisms have revealed a role for microRNAs in tuning tissue-specific gene expression. Here, we show that the relatively abundant and constitutively expressed miR-58 family of microRNAs sharply defines the tissue-specific expression of the broadly transcribed gene encoding PMK-2 p38 MAPK in Caenorhabditis elegans. Whereas PMK-2 functions redundantly with PMK-1 in the nervous system to regulate neuronal development and behavioral responses to pathogenic bacteria, the miR-58, miR-80, miR-81, and miR-82 microRNAs function redundantly to destabilize pmk-2 mRNA in non-neuronal cells with switch-like potency. Our data suggest a role for the miR-58 family in the establishment of neuronal-specific gene expression in C. elegans, and support a more general role for microRNAs in the establishment of tissue-specific gene expression.
Project description:PMK-1 is involved in the heat stress response of C. elegans, translocates to the nucleus upon heat exposure and influences the expression of chaperone genes, proteasomal subunits and protein-biosynthesis related genes. Differential Gene expression of WT and pmk-1 deletion mutant (KU25) after 5 hours at 35°C
Project description:Innate immunity in Caenorhabditis elegans requires a conserved PMK-1 p38 mitogen-activated protein kinase (MAPK) pathway that regulates the basal and pathogen-induced expression of immune effectors. The mechanisms by which PMK-1 p38 MAPK regulates the transcriptional activation of the C. elegans immune response have not been identified. Furthermore, in mammalian systems the genetic analysis of physiological targets of p38 MAPK in immunity has been limited. Here, we show that C. elegans ATF-7, a member of the conserved cyclic AMP-responsive element binding (CREB)/activating transcription factor (ATF) family of basic-region leucine zipper (bZIP) transcription factors and an ortholog of mammalian ATF2/ATF7, has a pivotal role in the regulation of PMK-1-mediated innate immunity. Genetic analysis of loss-of-function alleles and a gain-of-function allele of atf-7, combined with expression analysis of PMK-1-regulated genes and biochemical characterization of the interaction between ATF-7 and PMK-1, suggest that ATF-7 functions as a repressor of PMK-1-regulated genes that undergoes a switch to an activator upon phosphorylation by PMK-1. Whereas loss-of-function mutations in atf-7 can restore basal expression of PMK-1-regulated genes observed in the pmk-1 null mutant, the induction of PMK-1-regulated genes by pathogenic Pseudomonas aeruginosa PA14 is abrogated. The switching modes of ATF-7 activity, from repressor to activator in response to activated PMK-1 p38 MAPK, are reminiscent of the mechanism of regulation mediated by the corresponding ancestral Sko1p and Hog1p proteins in the yeast response to osmotic stress. Our data point to the regulation of the ATF2/ATF7/CREB5 family of transcriptional regulators by p38 MAPK as an ancient conserved mechanism for the control of innate immunity in metazoans, and suggest that ATF2/ATF7 may function in a similar manner in the regulation of mammalian innate immunity.
Project description:P38 mitogen-activated protein kinase (p38 MAPK) plays an important role in innate immunity and is activated by ultraviolet (UV) radiation. However, the molecular mechanism underlying UV stress remains unclear. In this study, we reported that UV activated PMK-1/p38 MAPK signaling via JKK-1 and MOM-4 in Caenorhabditis elegans. In C. elegans, different UV radiation doses resulted in PMK-1 phosphorylation. However, pmk-1 mutants failed to demonstrate an altered survival time in response to UV when compared with wild-type worms. Further analysis showed that JKK-1, but not SEK-1 mutants, displayed impaired PMK-1 activation following UV irradiation, suggesting that JKK-1 is the upstream MAP2K for the activation of PMK-1 in C. elegans under UV stimulation. UV-induced activation of PMK-1 was markedly reduced in MOM-4, but not in NSY-1 and DLK-1 mutant worms, suggesting that MOM-4 is the upstream MAP3K regulator of PMK-1 activation in response to UV stress in C. elegans. Additionally, daf-16 mutants displayed a shorter lifespan under UV stress, but UV-induced activation of PMK-1 was not markedly reduced in daf-16 and age-1 mutant worms. Our results revealed the signaling pathway involved in PMK-1 activation in C. elegans in response to UV radiation.
Project description:Yersinia pestis has acquired a variety of complex strategies that enable the bacterium to overcome defenses in different hosts and ensure its survival and successful transmission. A full-genome microarray analysis on Caenorhabditis elegans infected with Y. pestis shows enrichment in genes that are markers of innate immune responses and regulated by a conserved PMK-1/p38 MAPK. Consistent with a role in regulating expression of immune effectors, inhibition of PMK-1/p38 by mutation or RNA interference enhances susceptibility to Y. pestis. Further studies of mosaic animals where PMK-1/p38 is exclusively inhibited or overexpressed in a tissue-specific manner indicate that PMK-1/p38 controls expression of a CUB-like family of immune genes at the cell-autonomous level. Given the conserved nature of PMK-1/p38 MAPK-mediated signaling and innate immune responses, PMK-1/p38 MAPK may play a role in the immune response against Y. pestis in natural hosts.
Project description:PMK-1 is involved in the heat stress response of C. elegans, translocates to the nucleus upon heat exposure and influences the expression of chaperone genes, proteasomal subunits and protein-biosynthesis related genes.
Project description:Metformin, as the first-line oral drug for type 2 diabetes, has proven benefits against aging, cancer and cardiovascular diseases. But the influence of metformin to the immune response and its molecular mechanisms remain obscure. Metformin increases resistance to not only the Gram-negative pathogens Pseudomonas aeruginosa and Salmonella enterica but also the Gram-positive pathogens Enterococcus faecalis and Staphylococcus aureus. Meanwhile, metformin protects the animals from the infection by enhancing the tolerance to the pathogen infection rather than by reducing the bacterial burden. Through the screening of classical immune pathways in C. elegans, we find metformin enhances innate immunity through p38 MAPK pathway. Furthermore, activated p38/PMK-1 by metformin acts on the intestine for innate immune response. In addition, metformin-treated mice have increased resistance to P. aeruginosa PA14 infection and significantly increased the levels of active PMK-1. Therefore, promoted p38/PMK-1-mediated innate immunity by metformin is conserved from worms to mammals. Our work provides a conserved mechanism by which metformin enhances immune response and boosts its therapeutic application in the treatment of pathogen infection.
Project description:The p38 mitogen-activated protein kinase PMK-1 of Caenorhabditis elegans has been associated with heavy metal, oxidative and pathogen stress. Pmk-1 is part of an operon comprising three p38 homologues, with pmk-1 expression suggested to be regulated by the operon promoter. There are contradictory reports about the cellular localization of PMK-1. We were interested to study principles of pmk-1 expression and to analyze the role of PMK-1 under heat stress. Using a translational GFP reporter, we found pmk-1 expression to be driven by a promoter in front of pmk-1. PMK-1 was detected in intestinal cells and neurons, with a cytoplasmic localization at moderate temperature. Increasing temperature above 32 °C, however, induced a nuclear translocation of PMK-1 as well as PMK-1 accumulation near to apical membranes. Testing survival rates revealed 34-35 °C as critical temperature range, where short-term survival severely decreased. Mutants of the PMK-1 pathway (pmk-1Δ, sek-1Δ, mek-1Δ) as well as a mutant of JNK pathway (jnk-1Δ) showed significantly lower survival rates than wild-type or mutants of other pathways (kgb-1Δ, daf-2Δ). Rescue and overexpression experiments verified the negative effects of pmk-1Δ on heat tolerance. Studying gene expression by RNA-seq and semi-quantitative reverse transcriptase polymerase chain reaction revealed positive effects of the PMK-1 pathway on the expression of genes for chaperones, protein biosynthesis, protein degradation, and other functional categories. Thus, the PMK-1 pathway is involved in the heat stress responses of C. elegans, possibly by a PMK-1-mediated activation of the transcription factor SKN-1 and/or an indirect or direct PMK-1-dependent activation (hyperphosphorylation) of heat-shock factor 1.
Project description:We identified more than 300 genes inversely regulated by ced-3 and pmk-1 that enriched for epidermal stress response factors in C elegans
Project description:Infectious diseases caused by bacterial pathogens reduce the fitness of their associated host but are generally limited in duration. In order for the diseased host to regain any lost fitness upon recovery, a variety of molecular, cellular, and physiological processes must be employed. To better understand mechanisms underlying the recovery process, we have modeled an acute Pseudomonas aeruginosa infection in C. elegans using brief exposures to this pathogen and subsequent antibiotic treatment. To identify host genes altered during recovery from P. aeruginosa infection, we performed whole genome expression profiling. The analysis of this dataset indicated that the activity of the host immune system is down-regulated upon recovery and revealed shared and pathogen-specific host responses during recovery. We determined that the GATA transcription factor ELT-2 and the p38 MAP kinase PMK-1 are necessary for animals to successfully recover from an acute P. aeruginosa infection. In addition, we found that ELT-2 plays a more prominent and earlier role than PMK-1 during recovery. Our data sheds further light on the molecular mechanisms and transcriptional programs involved in recovery from an acute bacterial infection, which provides a better understanding of the entire infectious disease process.