ABSTRACT
Coagulation factor 2 receptor (F2R), also well-known as a protease-activated receptor 1 (PAR1), is the first known thrombin receptor and plays a critical role in transmitting thrombin-mediated activation of intracellular signaling in many types of cells. It has been known that bacterial infections lead to activation of coagulation systems, and recent studies suggest that PAR1 may be critically involved not only in mediating bacteria-induced detrimental coagulation, but also in innate immune and inflammatory responses. Community-acquired pneumonia, which is frequently caused by Streptococcus pneumoniae (S. pneumoniae), is characterized as an intra-alveolar coagulation and an interstitial neutrophilic inflammation. Recently, the role of PAR1 in regulating pneumococcal infections has been proposed. However, the role of PAR1 in pneumococcal infections has not been clearly understood yet. In this review, recent findings on the role of PAR1 in pneumococcal infections and possible underlying molecular mechanisms by which S. pneumoniae regulates PAR1-mediated immune and inflammatory responses will be discussed.