Cho H, Jeong DW, Liu Q, Yeo WS, Vogl T, Skaar EP, Chazin WJ, Bae T. Calprotectin Increases the Activity of the SaeRS Two Component System and Murine Mortality during Staphylococcus aureus Infections.
PLoS Pathog 2015;
11:e1005026. [PMID:
26147796 PMCID:
PMC4492782 DOI:
10.1371/journal.ppat.1005026]
[Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2014] [Accepted: 06/16/2015] [Indexed: 11/19/2022] Open
Abstract
Calprotectin, the most abundant cytoplasmic protein in neutrophils, suppresses the growth of Staphylococcus aureus by sequestering the nutrient metal ions Zn and Mn. Here we show that calprotectin can also enhance the activity of the SaeRS two component system (TCS), a signaling system essential for production of over 20 virulence factors in S. aureus. The activity of the SaeRS TCS is repressed by certain divalent ions found in blood or neutrophil granules; however, the Zn bound-form of calprotectin relieves this repression. During staphylococcal encounter with murine neutrophils or staphylococcal infection of the murine peritoneal cavity, calprotectin increases the activity of the SaeRS TCS as well as the production of proinflammatory cytokines such as IL-1β and TNF-α, resulting in higher murine mortality. These results suggest that, under certain conditions, calprotectin can be exploited by S. aureus to increase bacterial virulence and host mortality.
Staphylococcus aureus is an important human pathogen causing skin infections and a variety of life-threatening diseases such as pneumonia, sepsis, and toxic shock syndrome. Previous study showed that the growth of S. aureus in abscesses is suppressed by the host antimicrobial protein calprotectin, which sequesters Zn and Mn from bacterial usage. During bacterial infection, calprotectin also plays an important role in the production of proinflammatory cytokines. Although the antimicrobial activity of calprotectin has been well defined, it is not known how the proinflammatory property of calprotectin affects staphylococcal infection. In this study, we found that the Zn-binding property of calprotectin increases the pathogenic potential of S. aureus by enhancing the activity of the SaeRS two component system in S. aureus. We also found that, under certain infection conditions, the proinflammatory property of calprotectin is rather detrimental to host survival. Our study illustrates that the important antimicrobial protein can be exploited by S. aureus to render the bacterium a more effective pathogen, and provides an example of the intricate tug-of-war between host and a bacterial pathogen.
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