Staphylococcal lipoproteins and their role in bacterial survival in mice

Staphylococcus aureus expresses about 50 lipoproteins (Lpp), which are lipid-anchored in the membrane. The processing of the precursor to the mature Lpp is catalyzed by the phosphatidyl glycerol diacylglyceryl transferase (Lgt) and the lipoprotein-specific type II signal peptidase (LspA) leading to diacylated Lpp. Possibly another acyltransferase attaches a third fatty acid leading to triacylated Lpp. Lpp function as binding proteins for transport of nutrients across the microbial membrane and are involved in processing of other proteins, but most Lpp remain of predicted or unknown function. The di- or triacylated lipid structure is sensed by host pattern recognition receptor TLR2 and induces innate immune responses in professional and non-professional phagocytes. In the host, maturation of Lpp confers optimal metal ion - particularly iron - acquisition, it enhances staphylococcal invasion and phagocytosis, intracellular survival and persistence of infections. However, the advantages of Lpp maturation are counterbalanced by the capability to induce inflammation. In this review, we summarize the current knowledge about the role of Lpp in iron acquisition and TLR2 recognition in the host and describe the consequences of Lpp maturation for survival of S. aureus in the host.