Regulatory Role of the MisR/S Two-Component System in Hemoglobin Utilization in Neisseria meningitidis

Abstract

Outer membrane iron receptors are some of the major surface entities that are critical for meningococcal pathogenesis. The gene encoding the meningococcal hemoglobin receptor, HmbR, is both independently transcribed and transcriptionally linked to the upstream gene hemO, which encodes a heme oxygenase. The MisR/S two-component system was previously determined to regulate hmbR transcription, and its hemO and hmbR regulatory mechanisms were characterized further here. The expression of hemO and hmbR was downregulated in misR/S mutants under both iron-replete and iron-restricted conditions, and the downregulation could be reversed by complementation. No significant changes in expression of other iron receptors were detected, suggesting that the MisR/S system specifically regulates hmbR. When hemoglobin was the sole iron source, growth defects were detected in the mutants. Primer extension analysis identified a promoter upstream of the hemO-associated Correia element (CE) and another promoter at the proximal end of CE, and processed transcripts previously identified for other cotranscribed CEs were also detected, suggesting that there may be posttranscriptional regulation. MisR directly interacts with sequences upstream of the CE and upstream of the hmbR Fur binding site and thus independently regulates hemO and hmbR. Analysis of transcriptional reporters of hemO and hmbR further demonstrated the positive role of the MisR/S system and showed that the transcription of hmbR initiated from hemO was significantly reduced. A comparison of the effects of the misS mutation under iron-replete and iron-depleted conditions suggested that activation by the MisR/S system and iron-mediated repression by Fur act independently. Thus, the expression of hemO and hmbR is coordinately controlled by multiple independent regulatory mechanisms, including the MisR/S two-component system.

Neisseria gonorrhoeae Evades Calprotectin-Mediated Nutritional Immunity and Survives Neutrophil Extracellular Traps by Production of TdfH

“…Microarray studies have identified meningococcal TdfH as part of the MisR regulon (49). Additionally, MisRS has been shown to regulate the inner core structure of gonococcal lipooligosaccharide (LOS) and production of the hemoglobin receptor HmbR in N. meningitidis (50,51). When gonococci were grown under Zn-replete and Zn-depleted conditions, we found that the misR mutant derivative in the FA1090 background showed no difference in TdfH production compared to its parent (Fig.…”

Heme Synthesis and Acquisition in Bacterial Pathogens

“…In N. meningitidis, expression of hemO and hmbR is regulated by Fur as well as the MisRS TCS [204,205]. MisRS activates the expression of hemO and hmbR independent of Hb and iron concentration, which suggests an additional layer of regulation for Hb acquisition.…”

Fur-Mediated Global Regulatory Circuits in Pathogenic Neisseria Species

“…For example, in N. meningitidis, Fur-regulated hemO and hmbR were shown to be positively regulated by the two-component system MisR/S under both iron-depleted and -replete conditions (106). Transcription of N. meningitidis kat, which is activated by Fur, is also repressed by OxyR in the absence of H 2 O 2 and activated by OxyR with H 2 O 2 (49).…”