Mitogen-activated protein kinase (MAPK) cascades are conserved signalling modules that regulate responses to diverse extracellular stimuli, developmental cues and environmental stresses. A MAPK is phosphorylated and activated by a MAPK kinase (MAPKK), which is activated by an upstream protein kinase, such as Raf, Mos or a MAPKK kinase. @entity6771 , a MAPKK in the @entity375 @entity375 , is required for two developmental pathways: mating and invasive (filamentous) growth. @entity5677 and Fus3, the MAPK targets of @entity6771 , are required for mating, but their role in @entity851 has been unclear. Because no other @entity375 MAPK has been shown to function in @entity851 , it was proposed that @entity6771 may have non-MAPK targets. We show instead that @entity5677 is the principal target of @entity6771 in the invasive-growth response in both haploids and diploids. We demonstrate further that @entity5677 in its inactive form is a potent negative regulator of @entity851 . @entity6771 acts to relieve this negative regulation by switching @entity5677 from an inhibitor to an activator. These results indicate that this MAPK has a physiologically important function in its unactivated state. Comparison of normal and MAPK-deficient cells indicates that @entity1568 starvation and activated Ras stimulate filamentous growth through both MAPK-independent and MAPK-dependent means.

Inhibitory and activating functions for MAPK XXXX in the @entity375 filamentous-growth signalling pathway.

@entity6771 :: ('851396(Tax:4932)', 'Gene') :: ['Ste7'] @entity1568 :: ('MESH:D009584', 'Chemical') :: ['nitrogen'] @entity851 :: ('MESH:D006130', 'Disease') :: ['invasive growth'] @entity5677 :: ('852931(Tax:4932)', 'Gene') :: ['Kss1'] @entity375 :: ('4932', 'Species') :: ['yeast', 'Saccharomyces cerevisiae', 'S. cerevisiae']
@entity5677 :: (852931(Tax:4932),Gene) :: ['Kss1']
