Activation of PDE10 and PDE11

Background: The cyclic nucleotide phosphodiesterases PDE10 and PDE11 contain putatively regulatory GAF domains with unknown function. Results: Synthetic GAF domain ligands can activate both PDEs. Conclusion: PDE10 is activated by cAMP, whereas physiological ligand of the PDE11 GAF domains remains unknown. Significance: This is the first demonstration of a functional role of the PDE10 and PDE11 GAF domains. The most recently identified cyclic nucleotide phosphodiesterases, PDE10 and PDE11, contain a tandem of so called GAF domains in their N-terminal regulatory regions. In PDE2 and PDE5, the GAF domains mediate cGMP stimulation, however, their function in PDE10 and PDE11 remains controversial. Although the GAF domains of PDE10 mediate cAMPinduced stimulation of chimeric adenylyl cyclases, cAMP binding did not stimulate the PDE10 holoenzyme. Comparable data about cGMP and the PDE11 GAF domains exist. Here, we identified synthetic ligands for the GAF domains of PDE10 and PDE11 to reduce interference of the GAF ligand with PDE's catalytic reaction. With these ligands, GAFmediated stimulation of the PDE10 and PDE11 holoenzymes is demonstrated for the first time. Furthermore, PDE10 is shown to be activated by cAMP which paradoxically results in potent competitive inhibition of cGMP turnover by cAMP. PDE11, albeit susceptible to GAFdependent stimulation is not activated by the native cyclic nucleotides cAMP and cGMP. In sum, PDE11 can be stimulated by GAF domain ligands but its native ligand remains to be identified and PDE10 is the only PDE activated by cAMP. Phosphodiesterases (PDE) play important roles in the control of cyclic nucleotide signalling. To date, 11 families of PDEs have been identified differing in regulation and catalytic properties. With the exception of the photoreceptor PDE6, all PDEs are homodimers with conserved C-terminal catalytic domains and different N-terminal regulatory regions (for review see 1-3). PDE10 and PDE11 are the most recently discovered PDE families and both hydrolyse cAMP and cGMP (4-9). Each of these enzymes is encoded by one gene giving rise to several splice variants. For PDE10, 12 splice variants characterised by unique Nand C-terminal sequences have been described (10). The predominant forms are the membrane-bound PDE10A2 and a cytosolic form, PDE10A1 or PDE10A3 in humans or rats, respectively (11). For PDE11, four splice variants differing in the length of their N termini were found (9). Only PDE11A4 contains a complete tandem of GAF domains (see below); the other splice variants are truncations thereof (8). http://www.jbc.org/cgi/doi/10.1074/jbc.M111.263806 The latest version is at JBC Papers in Press. Published on November 21, 2011 as Manuscript M111.263806