Targeting of PKA, PKC and protein phosphatases to cellular microdomains

The intracellular responses to many distinct extracellular signals involve the direction of broad-based protein kinases and protein phosphatases to ca talyse quite specific protein phosphorylation/dephosphorylation events. It is now clear that such specificity is often achieved through subcellular ta rgeting of distinct pools of kinase or phosphatase towards particular subst rates at specific subcellular locations. Given the dynamic nature of protei n phosphorylation reactions, coordinated control of both kinase and phospha tases is often required and complexes formed by common scaffold or targetin g proteins exist to direct both kinase and phosphatase to the same subcellu lar location. In many cases more than one kinase or phosphatase is required and binding proteins which target more than one kinase or phosphatase have now been identified. This review summarizes recent findings relating to th e concept of targeting PKA, PKC and the major serine/threonine phosphatases , PP1, PP2A and PP2B, through the formation of multi-enzyme signalling comp lexes. (C) Harcourt Publishers Ltd.