CDK and MAPK Synergistically Regulate Signaling Dynamics via a Shared Multi-site Phosphorylation Region on the Scaffold Protein Ste5

WINTERS, MATTHEW J.; HOLLENSTEIN, DAVID MARIA; COLMAN-LERNER, ALEJANDRO; BUSH, ALAN; AMMERER, GUSTAV; REPETTO, MARÍA VICTORIA; REITER, WOLFGANG; PRYCIAK, PETER M.

MOLECULAR CELL

CELL PRESS

Lugar: United States; Año: 2018 vol. 69 p. 938 - 952

1097-2765

We report an unanticipated system of joint regulation by cyclin-dependent kinase (CDK) and mitogen- activated protein kinase (MAPK), involving collabora- tive multi-site phosphorylation of a single substrate. In budding yeast, the protein Ste5 controls signaling through a G1 arrest pathway. Upon cell-cycle entry, CDK inhibits Ste5 via multiple phosphorylation sites, disrupting its membrane association. Using quantita- tive time-lapse microscopy, we examined Ste5 mem- brane recruitment dynamics at different cell-cycle stages. Surprisingly, in S phase, where Ste5 recruit- ment should be blocked, we observed an initial recruitment followed by a steep drop-off. This delayed inhibition revealed a requirement for both CDK activity and negative feedback from the pathway MAPK Fus3. Mutagenesis, mass spectrom- etry, and electrophoretic analyses suggest that the CDK and MAPK modify shared sites, which are most extensively phosphorylated when both kinases are active and able to bind their docking sites on Ste5. Such collaborative phosphorylation can broaden regulatory inputs and diversify output dynamics of signaling pathways.