ABSTRACT
The pathogenic yeast Candida albicans and its derived molecules stimulate a wide range of macrophage secretory functions and may adapt to escape being killed by this phagocyte. In this study, phagocytosis of C. albicans and of the nonpathogenic yeast Saccharomyces cerevisiae was shown to be associated with phosphorylation of the mitogen-activated protein kinase (MAPK)/extracellularly regulated kinase (ERK) pathway in the absence of significant activation of either p38MAPK or stress-activated protein kinase/c-Jun N-terminal kinase. However, although 80% of endocytosed C. albicans survived after 1 h, 80% of S. cerevisiae cells were killed. Considerable quantitative differences were observed between the two species in the sequential phosphorylation of MAPK/ERK kinase (MEK), extracellularly regulated kinase-1, and 90-kDa-ribosomal S6 kinases. A lower level of activation of the pathway by C. albicans was associated with a species-specific overexpression of the MEK phosphatase MAPK phosphatase (MKP)-1. Killing of both C. albicans and S. cerevisiae could be reduced using PD98059, which mimics MKP-1 and inhibits MEK phosphorylation, suggesting that specific MKP-1 activation by C. albicans could contribute to its ability to escape the yeast lytic potential of macrophages.
