Protein phosphorylation dynamics: investigating a new dimension of regulatory control during mitosis

Protein phosphorylation regulates protein function in a switch-like manner.

Although each phosphorylation site only exists in two states (on/off), the frequency of switching between these states can vary dramatically.

Individual molecules that flash on and off rapidly can possess unique signalling properties, but these are difficult to study because dynamic information remains hidden from current analytical methods.

We will use heavy-[18O2]-ATP and mass spectrometry to quantify, for the first time, the rate that individual substrates are phosphorylated and dephosphorylated over time.

We will measure this globally and characterise different complexes during mitosis that rely on phosphorylation-dephosphorylation cycles to function correctly (BUBc/RepoMan/Centralspindlin/COMA).

We will study how these cycles control signal-switching and protein binding-release events, which we predict are needed to order mitotic progression, generate gradients of activity and/or assemble protein complexes. These concepts will be tested with purified components, mathematical modelling and quantitative microscopy.

Although we use mitosis as a model system, this work has far-reaching implications.

If binary phosphorylation events generate more complex outputs by varying their on/off rates, then any pathway could use this property to transmit information differently.

It is therefore crucial to investigate this phenomenon because these rates could be modulated to drive both signalling and disease.