Interaction with receptor for activated C kinase 1 (RACK1) sensitises PDE4D5 towards hydrolysis of cyclic AMP and activation by protein kinase C

Rebecca J Bird , George S. Baillie , Stephen J Yarwood (1)

1 Institute of Molecular Cell and Systems Biology

We have identified the Protein Kinase C (PKC) anchoring protein, Receptor for Activated C Kinase 1 (RACK1), as a specific binding partner for the cyclic AMP-specific phosphodiesterase, PDE4D5, suggesting a potential site for cross-talk between the PKC- and cyclic AMP-signalling pathways. Here we find that elevation of intracellular cyclic AMP with the b2-adrenoceptor agonist, isoproterenol, led to activation of PDE4 enzymes in the particulate and soluble fractions of HEK293 cells, whereas activation of PDE4D5 by isoproterenol and the PKC-activator, PMA, was restricted to the particulate fraction where it interacts with RACK1, however RACK1 is dispensable for anchoring PDE4D5 to the particulate fraction. Kinetic studies did demonstrate that RACK1 alters the conformation of particulate-associated PDE4D5 so that it more readily interacts with its substrate, cyclic AMP, and with rolipram, a PDE4 inhibitor that specifically targets the enzymes active site. Interaction with RACK1 was also essential for PKC-dependent, and ERK-independent, phosphorylation (on Ser 126) and activation of PDE4D5 in response to PMA and isoproterenol both of which trigger the recruitment of PKCa to RACK1. Together these results reveal novel signalling cross-talk, whereby RACK1 mediates PKC-dependent activation of PDE4D5 in the particulate fraction of HEK293 cells in response to elevations in intracellular cyclic AMP.

Mots clés: Life Sciences

Rebecca J Bird, George S. Baillie, Stephen J Yarwood. Interaction with receptor for activated C kinase 1 (RACK1) sensitises PDE4D5 towards hydrolysis of cyclic AMP and activation by protein kinase C. Biochemical Journal, 2010, 432 (1), pp.207-216. ⟨10.1042/BJ20101010⟩. ⟨hal-00529107⟩