title: CRP-Cyclic AMP Regulates the Expression of Type 3 Fimbriae via Cyclic di-GMP in Klebsiella pneumoniae.
abstract: 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.
authors.affiliation: School of Chinese Medicine, China Medical University, Taichung, Taiwan, Republic of China.
authors.forename: Ching-Ting
authors.initials: CT
authors.lastname: Lin
authors.affiliation: Division of Urology, Taichung Tzu Chi Hospital, The Buddhist Tzu Chi Medical Foundation, Taichung, Taiwan, Republic of China.|Tzu Chi University School of Post-Baccalaureate Chinese Medicine, Hualien, Taiwan, Republic of China.
authors.forename: Tien-Huang
authors.initials: TH
authors.lastname: Lin
authors.affiliation: Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan, Republic of China.
authors.forename: Chien-Chen
authors.initials: CC
authors.lastname: Wu
authors.affiliation: School of Chinese Medicine, China Medical University, Taichung, Taiwan, Republic of China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wan
authors.affiliation: School of Chinese Medicine, China Medical University, Taichung, Taiwan, Republic of China.
authors.forename: Chun-Fa
authors.initials: CF
authors.lastname: Huang
authors.affiliation: Department of Biological Science and Technology, National Chiao Tung University, Hsinchu, Taiwan, Republic of China.
authors.forename: Hwei-Ling
authors.initials: HL
authors.lastname: Peng
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002097:C-Reactive Protein / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D007711:Klebsiella pneumoniae / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; C062025:bis(3',5')-cyclic diguanylic acid; D002097:C-Reactive Protein; D000242:Cyclic AMP; D006152:Cyclic GMP; D005947:Glucose