C3 as substrate for adhesion of Streptococcus pneumoniae.
The ability of choline-binding protein A (CbpA) of Streptococcus pneumoniae to bind the third component of complement (C3) suggests possible interactions with opsonic C3 in the bloodstream or with C3 secreted by epithelial cells. The latter possibility was investigated by measuring C3 in supernatants of resting and cytokine-activated monolayers of type II pulmonary epithelial cells (A549 cells). Expression of C3 on the epithelial cell surface was confirmed by immunofluorescence. Epithelially produced C3 bound to CbpA, as determined by Western blot test. cbpa(-) mutants and lysates therefrom failed to bind C3, were completely deficient in adhesion to a matrix in which C3 was the sole substrate, and demonstrated a moderate yet significant decrease in adhesion to type II pulmonary epithelial cells. These results confirm the interaction of the pneumococcal protein CbpA and its substrate, C3, in 2 in vitro models of adhesion.
Department of Pediatrics, Division of Infectious Diseases, and Department of Microbiology, Immunology and Molecular Pathobiology, University of Minnesota, Minneapolis, USA.
B L
BL
Smith
M K
MK
Hostetter
D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D003176:Complement C3 / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism; D008168:Lung / Q000378:metabolism / Q000382:microbiology; D009154:Mutation; D011485:Protein Binding; D020545:Respiratory Mucosa / Q000378:metabolism / Q000382:microbiology; D013296:Streptococcus pneumoniae / Q000472:pathogenicity* / Q000648:ultrastructure; D014407:Tumor Cells, Cultured
D001426:Bacterial Proteins; D003176:Complement C3; D016209:Interleukin-8