title: Separate roles of PKA and EPAC in renal function unraveled by the optogenetic control of cAMP levels in vivo.
abstract: Cyclic AMP (cAMP) is a ubiquitous second messenger that regulates a variety of essential processes in diverse cell types, functioning via cAMP-dependent effectors such as protein kinase A (PKA) and/or exchange proteins directly activated by cAMP (EPAC). In an intact tissue it is difficult to separate the contribution of each cAMP effector in a particular cell type using genetic or pharmacological approaches alone. We, therefore, utilized optogenetics to overcome the difficulties associated with examining a multicellular tissue. The transgenic photoactive adenylyl cyclase bPAC can be activated to rapidly and reversibly generate cAMP pulses in a cell-type-specific manner. This optogenetic approach to cAMP manipulation was validated in vivo using GAL4-driven UAS-bPAC in a simple epithelium, the Drosophila renal (Malpighian) tubules. As bPAC was expressed under the control of cell-type-specific promoters, each cAMP signal could be directed to either the stellate or principal cells, the two major cell types of the Drosophila renal tubule. By combining the bPAC transgene with genetic and pharmacological manipulation of either PKA or EPAC it was possible to investigate the functional impact of PKA and EPAC independently of each other. The results of this investigation suggest that both PKA and EPAC are involved in cAMP sensing, but are engaged in very different downstream physiological functions in each cell type: PKA is necessary for basal secretion in principal cells only, and for stimulated fluid secretion in stellate cells only. By contrast, EPAC is important in stimulated fluid secretion in both cell types. We propose that such optogenetic control of cellular cAMP levels can be applied to other systems, for example the heart or the central nervous system, to investigate the physiological impact of cAMP-dependent signaling pathways with unprecedented precision.
authors.affiliation: Institute for Biology/Genetics, Free University Berlin, D-14195 Berlin, Germany.
authors.forename: Marina
authors.initials: M
authors.lastname: Efetova
authors.forename: Linda
authors.initials: L
authors.lastname: Petereit
authors.forename: Kamil
authors.initials: K
authors.lastname: Rosiewicz
authors.forename: Gayle
authors.initials: G
authors.lastname: Overend
authors.forename: Florian
authors.initials: F
authors.lastname: Haußig
authors.forename: Bernhard T
authors.initials: BT
authors.lastname: Hovemann
authors.forename: Pablo
authors.initials: P
authors.lastname: Cabrero
authors.forename: Julian A T
authors.initials: JA
authors.lastname: Dow
authors.forename: Martin
authors.initials: M
authors.lastname: Schwärzel
mesh_terms: D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D030801:Animals, Genetically Modified; D002450:Cell Communication; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000502:physiology*; D004847:Epithelial Cells / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D008317:Malpighian Tubules / Q000378:metabolism / Q000502:physiology*; D062308:Optogenetics; D009928:Organ Specificity; D015398:Signal Transduction
chemical_list: D029721:Drosophila Proteins; C542725:Epac protein, Drosophila; D020662:Guanine Nucleotide Exchange Factors; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases