Staphylococcus aureus LukAB stem domain unlatching influences toxin oligomerization

ABSTRACT: Staphylococcus aureus (S. aureus) is a serious global pathogen that causes a diverse range of invasive diseases and is notorious for antibiotic resistance. S. aureus utilizes a family of pore-forming toxins, known as bi component leukocidins, to evade the host immune response and promote infection. Among these is LukAB (leukocidin A, leukocidin B), a toxin that is secreted as a soluble heterodimer and assembles into an octameric beta barrel pore that is embedded in the host cell membrane, resulting in death of the host cell. The established cellular receptor for LukAB is CD11b of the Mac1 complex. LukAB variants from S. aureus clonal complexes (CC) 30 and 45 were recently described to use the proton channel hydrogen voltage gated channel 1 (HVCN1) as a receptor. Here we show that HVCN1 is an essential receptor used by all LukAB variants representing the major S. aureus clonal complexes, including CC8 LukAB, which belongs to the most prevalent lineage responsible for skin and soft tissue infections in the United States. We demonstrate that while each receptor is sufficient to recruit CC8 LukAB to the plasma membrane of phagocytes, both receptors are required for maximal lytic activity. Why LukAB requires two receptors, and how each of these receptors contribute to pore-formation remains unknown. To begin to resolve this, we performed an alanine scanning mutagenesis screen to identify mutations that allow CC8 LukAB to bypass the requirement for CD11b. We discovered thirty mutations primarily localized in the stem domain of LukA and LukB that enabled LukAB to exhibit enhanced cytotoxicity in the absence of CD11b. Using crosslinking, electron microscopy, and hydroxyl radical protein footprinting experiments we show these mutations alter the solvent accessibility of the stem domain which prime LukAB for oligomerization. Together, our data allow us to introduce a role for CD11b beyond toxin recruitment to the target cell: we propose a model in which CD11b binding unlatches the membrane penetrating stem domains of LukAB, and this change in flexibility promotes toxin oligomerization, driving pore-formation. The mass spectrometric raw files for the hydroxyl radical footprinting experiment are included here.

INSTRUMENT(S): Q Exactive HF-X

ORGANISM(S): Staphylococcus Aureus (ncbitaxon:1280)

SUBMITTER: Beatrix Ueberheide  

PROVIDER: MSV000092897 | MassIVE |

SECONDARY ACCESSION(S): PXD045499

REPOSITORIES: MassIVE