Molecular characterization and identification of proteins regulated by Hfq in Neisseria meningitidis.
Bottom Line: Using proteomics, the expression of 28 proteins was found to be significantly affected upon deletion of hfq.One of the differentially expressed proteins, GdhA, was identified as an essential virulence factor for establishment of sepsis in an animal model, studied earlier.These results show that in N. meningitidis Hfq is involved in the regulation of a variety of components contributing to the survival and establishment of meningococcal disease.
Hfq is a highly conserved pleiotropically acting prokaryotic RNA-binding protein involved in the post-transcriptional regulation of many stress-responsive genes by small RNAs. In this study, we show that Hfq of the strictly human pathogen Neisseria meningitidis is involved in the regulation of expression of components involved in general metabolic pathways, iron metabolism and virulence. A meningococcal hfq deletion strain (H44/76Deltahfq) is impaired in growth in nutrient-rich media and does not grow at all in nutrient-limiting medium. The growth defect was complemented by expression of hfq in trans. Using proteomics, the expression of 28 proteins was found to be significantly affected upon deletion of hfq. Of these, 20 proteins are involved in general metabolism, among them seven iron-responsive genes. Two proteins (PilE, TspA) are involved in adherence to human cells, a step crucial for the onset of disease. One of the differentially expressed proteins, GdhA, was identified as an essential virulence factor for establishment of sepsis in an animal model, studied earlier. These results show that in N. meningitidis Hfq is involved in the regulation of a variety of components contributing to the survival and establishment of meningococcal disease.
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Mentions: The complete genome sequences of four meningococcal, two strains of the closely related human pathogen Neisseria gonorrhoeae and one commensal neisserial species (Neisseria lactamica) are known (Parkhill et al., 2000; Tettelin et al., 2000; Bentley et al., 2007; Chung et al., 2008; Peng et al., 2008). The amino acid sequence of Hfq of the meningococcal strain used in this study (H44/76) is identical to the Hfq sequence of meningococcal strain FAM18 and 98% identical to the sequences of the other three meningococcal strains. In addition, the sequence of H44/76 is 98% identical to gonococcal Hfq and 95% identical to the Hfq sequence of N. lactamica. The H44/76 neisserial Hfq amino acid sequence shows 63% and 60% identities to Hfq proteins of E. coli and Vibrio spp., respectively (Fig. 1). Of importance, hardly any amino acid substitutions in the meningococcal Hfq sequence, compared with those of E. coli and Vibro spp., are observed in highly conserved regions of the protein shown to be important for functionality (Fig. 1) (Schumacher et al., 2002).