Non-canonical regulation of cAMP-dependent protein kinase in the synapse (360G-Wellcome-104194_Z_14_A)

This project will investigate a mechanism for regulating cAMP-dependent protein kinase (PKA) that is not founded on cAMP fluctuations. Neuronal PKA activity is largely dictated by rates of binding and release of PKA catalytic subunits from inhibitory type II regulatory (RII) subunits. The balance of these rates determines the fraction of free catalytic subunits. According to the canonical model, reductions in PKA activity follow from decreases in cAMP concentration since cAMP-free RII subunits bind catalytic subunits with higher affinity. Dephosphorylation of a serine in the RII autoinhibitory sequence also generates a form of RII with higher affinity for catalytic subunits, but no plausible mechanism has been uncovered that involves regulation of this site. We will investigate whether anchoring of phosphatases in complex with RII subunits enables suppression of PKA activity by shifting the Michaelis constant for RII dephosphorylation into the physiological range. We will build and test models of neuronal PKA signalling to understand the kinetic basis of this mode of PKA regulation. We will examine whether RII dephosphorylation within a synaptic signalling complex is necessary for the induction of long-term depression of synaptic strength. Finally, we will investigate interplay between Ca2+ signalling and this novel form of PKA regulation.