Regulation of MAPK Signaling in Yeast

Abstract

Mitogen activated protein kinase (MAPK) pathways orchestrate the response of cells to their changing extracellular environment. Budding yeast has proven to be a useful model system to elucidate the basic principles of these complex signal transduction processes. Yeast cells use six MAP-kinases, which respond to diverse conditions such as pheromone signals, osmolarity, cell wall stress and nutritional status. Depending on the external and internal conditions, multiple signals must be integrated leading to a defined output and different signaling kinetics. In this review, we will discuss the molecular architecture of the mating and high-osmolarity-glycerol (HOG) MAPK pathways, and compare their underlying signaling parameters. These two pathways use shared components and by contrasting their activation and regulation we try to deduce common and specific principles for MAPK signaling in yeast. Among those, we will summarize and discuss recent findings, which shed light on positive and negative feedback mechanisms. Finally, we will highlight the importance of quantitative measurements in single cells, which are necessary to unravel stochastic cell-to-cell variations and account for the dynamic signaling kinetics.