The Human Antimicrobial Protein Calgranulin C Participates in Control of Helicobacter pylori Growth and Regulation of Virulence

Abstract

f During infectious processes, antimicrobial proteins are produced by both epithelial cells and innate immune cells. Some of these antimicrobial molecules function by targeting transition metals and sequestering these metals in a process referred to as "nutritional immunity." This chelation strategy ultimately starves invading pathogens, limiting their growth within the vertebrate host. Recent evidence suggests that these metal-binding antimicrobial molecules have the capacity to affect bacterial virulence, including toxin secretion systems. Our previous work showed that the S100A8/S100A9 heterodimer (calprotectin, or calgranulin A/B) binds zinc and represses the elaboration of the H. pylori cag type IV secretion system (T4SS). However, there are several other S100 proteins that are produced in response to infection. We hypothesized that the zinc-binding protein S100A12 (calgranulin C) is induced in response to H. pylori infection and also plays a role in controlling H. pylori growth and virulence. To test this, we analyzed gastric biopsy specimens from H. pylori-positive and -negative patients for S100A12 expression. These assays showed that S100A12 is induced in response to H. pylori infection and inhibits bacterial growth and viability in vitro by binding nutrient zinc. Furthermore, the data establish that the zinc-binding activity of the S100A12 protein represses the activity of the cag T4SS, as evidenced by the gastric cell "hummingbird" phenotype, interleukin 8 (IL-8) secretion, and CagA translocation assays. In addition, high-resolution field emission gun scanning electron microscopy (FEG-SEM) was used to demonstrate that S100A12 represses biogenesis of the cag T4SS. Together with our previous work, these data reveal that multiple S100 proteins can repress the elaboration of an oncogenic bacterial surface organelle. Helicobacter pylori is a Gram-negative member of the Epsilonproteobacteria commonly found in the human stomach (1). More than 50% of the world's population is chronically infected with H. pylori, despite a robust immune response to this bacterium (2, 3). The vast majority of infected persons exhibit no symptoms of disease; however, the presence of this pathogen can increase the risk of negative outcomes, including duodenal ulcer, dysplasia, mucosa-associated lymphoid tissue (MALT) lymphoma, and invasive gastric cancer (4). Negative outcomes of H. pylori infection are associated with multiple factors, including host genetics, environmental contributions such as diet and smoking, and bacterial virulence properties.One major virulence factor that contributes to H. pylori-associated disease outcomes is the cag pathogenicity island-encoded type IV secretion system (cag T4SS) (5). The cag T4SS is a macromolecular nanomachine responsible for translocating substrates, including peptidoglycan and the oncogenic effector molecule CagA, into host epithelial cells (6). The translocation activity of the cag T4SS leads to multiple consequences in host cell biology, including cytoskeletal rearrangements, indu...

Bacterial Strategies to Maintain Zinc Metallostasis at the Host-Pathogen Interface

“…CP also binds Fe II with high affinity, hinting at a broader anti-bacterial function of this protein (14). S100 A7 (psoriasin) and A12 (calgranulin C) are other well studied members of this class of proteins with metal-sequestering antimicrobial activity (15,16).…”

Transition Metals and Virulence in Bacteria

“…Psoriasin also contributes to mucosal immunity on the tongue and in the vagina (92, 94). Similarly, S100A12 (calgranulin C), which binds both Zn 2+ and Cu 2+ , is induced in H. pylori infection and limits bacterial growth through zinc chelation (56). …”

“…These findings raise questions as to the mechanism of copper limitation in these niches (e.g., cerebrospinal fluid). Although the host immune protein S100A12 binds copper in addition to zinc, its antimicrobial activity against H. pylori appears to be restricted to zinc chelation (56). Improved understanding of the importance of cobalt, nickel, and copper for bacterial pathogenesis will determine whether the host actively limits these metals through nutritional immunity and whether bacterial pathogens are affected by their limitation or can counteract host-mediated limitation.…”

Zinc’ing it out: zinc homeostasis mechanisms and their impact on the pathogenesis of human pathogen group A streptococcus

“…The members of the S100 family are major players in imposing host-mediated zinc limitation at bacterial infection sites. 39–42 Among the various S100 proteins, calprotectin (CP) is the best-characterized antimicrobial zinc chelator. 43–47 CP is a heterodimer of S100A8 and S100A9 proteins, which is present abundantly at various bacterial colonization surfaces in the host.…”

“…43,44,47 CP is released from the neutrophils and the extracellular CP exerts its antimicrobial activity against several human pathogens by calcium-dependent chelation of zinc and manganese. 30,42,46–48,51–56 Structurally, each subunit of CP has two calcium-binding EF-hand motifs and occupancy of calcium at each EF-hand motif is necessary for transition metal binding by CP. 45,46 In addition, CP heterodimer has two metal binding sites located at the intersubunit dimerization interface.…”