Protein kinase antagonists inhibit invasion of mammalian cells by Fonsecaea pedrosoi

Abstract

The phosphorylation process is an important mechanism of cell signalling and regulation. It has been implicated recently in defence strategies against a variety of pathogens that alter host signalling pathways in order to facilitate their invasion and survival within host cells. In this study, the involvement of protein kinases (PKs) has been investigated in attachment and invasion by the pathogenic fungusFonsecaea pedrosoiwithin epithelial cells and macrophages. The use of the PK inhibitors staurosporine, genistein and calphostin C prior to infection provided significant information about the role played by PKs in theF. pedrosoi–host cell interaction. All three PK inhibitors could reduce cell invasion byF. pedrosoisignificantly. Pre-treatment of macrophages, epithelial cells or conidia with PK inhibitors decreased fungus invasion, and this effect could be overcome by okadaic acid, a phosphatase inhibitor. Immunofluorescence assays showed that tyrosine residues were phosphorylated in the first step of the interaction, while serine residues were phosphorylated in the subsequent step of entry of the parasite into the host cell. These results suggest that both host-cell and conidium PK activities are important in the interaction process, playing a significant role in cell invasion.