PKA can adopt structural or enzymatic roles depending on its anchoring site

Protein kinase A (PKA) assumes different roles depending on where it is anchored. This versatile kinase is a key player in cAMP signaling, with its spatial specificity determined by A-kinase anchoring proteins (AKAPs). However, determining the specific functions of PKA pools that are anchored at individual sites has proven challenging due to the lack of methods that can isolate anchoring at defined locations.

In this study, researchers developed a SpyCatcher-SpyTag-based replacement strategy that allows for a direct comparison of AKAP function with and without type II PKA regulatory (RII) subunit anchoring in live signaling environments. When RII was anchored to AKAP79 or AKAP1, it led to distinct phosphorylation-dependent effects. For instance, it caused the membrane recruitment of the catalytic subunit and regulated mitochondrial morphology.

On the other hand, when MAP2 anchored RII, it triggered phosphorylation-independent microtubule straightening, increased the formation of widely spaced microtubule bundles, and facilitated dendritic arborization. This structural function was also observed when native MAP2-RII binding occurred, and it required an intact cAMP-binding pocket in the second cyclic nucleotide-binding domain.

These findings demonstrate that AKAP-bound PKA can act as either an enzymatic or structural component, offering a generalizable approach to dissect compartmentalized kinase signaling.