Binding of the non-typeable Haemophilus influenzae lipooligosaccharide to the PAF receptor initiates host cell signalling

Abstract

SummaryNon-typeable Haemophilus influenzae (NTHi) invades host cells by binding of the platelet-activating factor (PAF) receptor via lipooligosaccharide (LOS) glycoforms containing phosphorylcholine (ChoP). The effect of NTHi infection on host cell signalling and its role in NTHi invasion was examined. The infection of human bronchial epithelial cells with NTHi 2019 increased cytosolic Ca 21 levels, and the invasion of bronchial cells by NTHi 2019 was inhibited by pretreatment with the cell-permeant intracellular Ca 21 chelator BAPTA-AM (P 0.022) or thapsigargin (P 0.016). Cytosolic inositol phosphate (IP) levels were also increased after infection with NTHi 2019 (P , 0.001), but not after infection with isogenic mutants expressing altered LOS glycoforms lacking ChoP. PAF receptor antagonist reduced NTHi 2019-stimulated IP production in a dosedependent manner. NTHi 2019 invasion was inhibited by pertussis toxin (PTX) and the phosphatidylinositol-3-kinase inhibitors wortmannin and LY294002. The less invasive strain NTHi 7502 also initiated IP production, but was unaffected by PAF receptor antagonist or PTX. These data demonstrate that the binding of the PAF receptor by NTHi initiates receptor coupling to a PTXsensitive heterotrimeric G protein complex, resulting in a multifactorial host cell signal cascade and bacterial invasion. Moreover, the data suggest that NTHi strains initiate cell signalling and invade by different mechanisms, and that invasion mediated by PAF receptor activation is more efficient than macropinocytosis.

Phosphorylcholine Decreases Early Inflammation and Promotes the Establishment of Stable Biofilm Communities of Nontypeable Haemophilus influenzae Strain 86-028NP in a Chinchilla Model of Otitis Media

“…For many of these bacteria, carriage in vivo enriches for bacterial populations that express higher levels of PCho (6,45,50,52,53). Contributions of PCho to the persistence of NTHi in vivo include increased adherence to and invasion of airway epithelial cells (39,40,42), resistance to some host antimicrobials (23), and diminished potency of LOS as an inflammatory agonist (55). The results of this study show that PCho promotes the establishment and persistence of NTHi communities within the chinchilla middle ear.…”

Concepts and Mechanisms: Crossing Host Barriers

“…The laminin receptor (LR) and platelet activating factor receptor (PAFr) have been identified as common portals of CNS entry for the leading meningeal pathogens such as E. coli K1 Kim et al 2005a), Neisseria meningitidis (Virji et al 1993), Streptococcus pneumoniae (Ring et al 1998;Orihuela et al 2009), and Haemophilus influenzae (Swords et al 2001). LR was identified to function as a receptor for CNF-1 of E. coli K1 Kim et al 2005a), PilQ and PorA of N. meningitidis, CbpA of S. pneumoniae, and OmpP2 of H. influenzae (Orihuela et al 2009).…”

Role of p38 MAP Kinase and Transforming Growth Factor-β Signaling in Transepithelial Migration of Invasive Bacterial Pathogens

“…Mice lacking TLR2, for example, are more susceptible to overwhelming infection with S. pneumoniae (12). In addition, both species express phosphorylcholine on their surface and can bind and initiate signaling through mimicry of platelet activating factor and ligation of its receptor (2,13).…”