Figure 7.

Model of the lipid asymmetry signaling pathway. A signal from moderate increases in pH induces expression of the pH-responsive genes through activation of the Rim101 pathway. The same Rim101 pathway transduces a signal resulting in Rsb1 expression, but other pathways, such as that involving Mot3 and Mck1, are also required. Changes in lipid asymmetry, caused either by a flip or flop mutation, induce activation of the Rim101 pathway and probably of the Mot3/Mck1-related pathways as well. However, these pathways are activated differently by the flip or flop mutation. The Rim101 pathway is activated more strongly by the flip mutation, whereas other pathways seem to be activated more predominantly by the flop mutation. Pdr1 may act as a basic transcription factor, since little Rsb1 expression was observed in pdr1Δ cells.