Differential regulation by Toll-like receptor agonists reveals that MCPIP1 is the potent regulator of innate immunity in bacterial and viral infections.

Toll-like receptors (TLRs) are key molecules in innate immunity that recognize a variety of pathogen-associated molecular patterns. Activation of TLRs by their agonists initiates several signaling cascades, which eventually result in the expression of immune modifiers. Despite the fact that MCPIP1 is reported as an important immune regulator involved in macrophage activation, modulation of its expression by all known TLR agonists has never been documented. In this study, we present for the first time that in human monocyte-derived macrophages all TLR agonists, except CpG, markedly induced the expression of MCPIP1. The level of the induced transcript, as well as the protein and time of their appearance varied depending on the agonist. Furthermore, we confirmed the strong and differential upregulation of MCPIP1 during bacteria, virus and fungus infection. MCPIP1 belongs to a group of early-response genes; however, in the present study, we show for the first time the sustained high level of MCPIP1 expression during long-term Staphylococcus aureus infection. Taken together, our results implicate MCPIP1 as a potent regulator of innate immunity, which can be strongly engaged in the pathogenesis of acute and chronic infective diseases.