Surfactant protein A (SP-A)-mediated clearance of Staphylococcus aureus involves binding of SP-A to the staphylococcal adhesin eap and the macrophage receptors SP-A receptor 210 and scavenger receptor class A

J Biol Chem. 2011 Feb 11;286(6):4854-70. doi: 10.1074/jbc.M110.125567. Epub 2010 Dec 1.

Abstract

Staphylococcus aureus causes life-threatening pneumonia in hospitals and deadly superinfection during viral influenza. The current study investigated the role of surfactant protein A (SP-A) in opsonization and clearance of S. aureus. Previous studies showed that SP-A mediates phagocytosis via the SP-A receptor 210 (SP-R210). Here, we show that SP-R210 mediates binding and control of SP-A-opsonized S. aureus by macrophages. We determined that SP-A binds S. aureus through the extracellular adhesin Eap. Consequently, SP-A enhanced macrophage uptake of Eap-expressing (Eap(+)) but not Eap-deficient (Eap(-)) S. aureus. In a reciprocal fashion, SP-A failed to enhance uptake of Eap(+) S. aureus in peritoneal Raw264.7 macrophages with a dominant negative mutation (SP-R210(DN)) blocking surface expression of SP-R210. Accordingly, WT mice cleared infection with Eap(+) but succumbed to sublethal infection with Eap- S. aureus. However, SP-R210(DN) cells compensated by increasing non-opsonic phagocytosis of Eap(+) S. aureus via the scavenger receptor scavenger receptor class A (SR-A), while non-opsonic uptake of Eap(-) S. aureus was impaired. Macrophages express two isoforms: SP-R210(L) and SP-R210(S). The results show that WT alveolar macrophages are distinguished by expression of SP-R210(L), whereas SR-A(-/-) alveolar macrophages are deficient in SP-R210(L) expressing only SP-R210(S). Accordingly, SR-A(-/-) mice were highly susceptible to both Eap(+) and Eap(-) S. aureus. The lungs of susceptible mice generated abnormal inflammatory responses that were associated with impaired killing and persistence of S. aureus infection in the lung. In conclusion, alveolar macrophage SP-R210(L) mediates recognition and killing of SP-A-opsonized S. aureus in vivo, coordinating inflammatory responses and resolution of S. aureus pneumonia through interaction with SR-A.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesins, Bacterial / genetics
  • Adhesins, Bacterial / metabolism*
  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Humans
  • Lung / metabolism
  • Macrophages, Alveolar / metabolism*
  • Macrophages, Peritoneal / metabolism*
  • Mice
  • Mice, Knockout
  • Phagocytosis / physiology
  • Pneumonia, Staphylococcal / genetics
  • Pneumonia, Staphylococcal / metabolism*
  • Pulmonary Surfactant-Associated Protein A / genetics
  • Pulmonary Surfactant-Associated Protein A / metabolism*
  • Receptors, Cell Surface / genetics
  • Receptors, Cell Surface / metabolism*
  • Staphylococcus aureus / genetics
  • Staphylococcus aureus / metabolism*

Substances

  • Adhesins, Bacterial
  • Pulmonary Surfactant-Associated Protein A
  • Receptors, Cell Surface
  • surfactant protein A receptor