Regulation of the colonization and invasive phenotypes by protease activity in Staphylococcus aureus, analysis of fibronectin-binding protein (FNBP) and V8 protease as paradigms of this concept

grantor: University of Toronto'Staphylococcus aureus' infects nearly every tissue and organ system in the human body, and this versatility has been attributed to an ability to rapidly alter virulence factor production such that a colonization phenotype can be rapidly exchanged for one favoring invasion. Cell surface FnBPs promote adhesion to traumatized host tissue, and are maximally expressed during exponential growth. Conversely, secreted V8 protease (SspA) expression is repressed during exponential growth, and upregulated as cells approach stationary phase. Herein, we hypothesized that the colonization and invasive phenotypes of 'S. aureus' can be significantly affected by sued proteases, using FnBP and SspA as paradigms of these phases of infection. Initially we addressed factors that contribute to the considerable variation in Fn-binding observed among 'S. aureus' clinical isolates, as this may be important for developing adhesion-blocking antibodies. The ' fnb' locus was polymorphic in a small number of clinical isolates in terms of the number of 'fnb' genes and/or repeated Fn-binding D-motifs. Furthermore, functional antigenic variation was observed in the D3-like motif of the epidemic strain CMRSA-1. However, these observations were not related to variations in Fn-binding. In contrast, variation in Fn-binding among MRSA was inversely related to protease activity, and previous work in our lab demonstrated a role for SspA in degrading cell-surface FnBP. Therefore, we hypothesized that SspA modifies the colonization and invasive phenotypes of 'S. aureus'. Non-polar inactivation of 'ssp'A in 'S. aureus' SP6391 ('ssp'APh.D