Dissecting the PDE4d orthologue Dunce isoform functions in Drosophila melanogaster

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In humans as in the fruit fly Drosophila melanogaster several phosphodiesterases (PDEs) exit. They hydrolyze cAMP to AMP and terminate cAMP signaling. One of the most important questions related to phosphodiesterase function was already raised by Houslay in 2010: “Why are there so many different isoforms generated when all of them hydrolyze cAMP?” While there is emerging evidence that sub-cellular micro-domains of cAMP are involved in the regulation of cAMP signaling specificity due to targeted PDE activity and cAMP effector proteins to different domains in the cell, our knowledge is far from comprehensive. We propose to use Drosophila melanogaster to diessect the function of the Pde4d orthologue Dunce on subcellular, on neuronal and behavioral level. We want to investigate whether different isoforms of the Pde4D orthologue Dunce are required to set up distinct cAMP micro-domains in neurons. We focus our analysis on Dunce for serval reasons. First Dunce is the only cAMP specific PDE in Drosophila, second we have previosly shown that different Dunce isoforms are expressed in different sub-cellular compartments. Third dunce mutants differ in their defects in neuronal plasticity. To measure changes in neuronal plasticity and function we will analyze the function of Dunce in associative aversive olfactory learning and memory and neuron morphology. In particular we want to use the differences on behavioral, cellular und subcellular level to address whether different Dunce isoforms act in the same neurons in different subcellular domains to regulate cAMP signaling. Further we want to determine whether the same isoform regulates in different neurons similar forms of neuronal plasticity. Finally we will investigate whether subcellular changes of PDE activity are restricted to specific cellular sites or whether these changes extend over the whole neuron. Towards this end, we will use genetic, molecular-genetic, imagine techniques and behavioral analysis. The obtained results will shed light on how in Drosophila cellular cAMP domains are set up and how different Dunce isoforms contribute to changes of neuronal plasticity.