title: The GAFa domain of phosphodiesterase-6 contains a rod outer segment localization signal.
abstract: Photoreceptor phosphodiesterase-6 (PDE6) is a peripheral membrane protein synthesized in the inner segment of photoreceptor cells. Newly synthesized PDE6 is transported to the outer segment (OS) where it serves as a key effector enzyme in the phototransduction cascade. Proper localization of PDE6 in photoreceptors is critically important to the function and survival of photoreceptor cells. The mechanism of PDE6 transport to the OS remains largely unknown. In this study, we investigated potential OS targeting signals of PDE6 by constructing cGMP-binding, cGMP-specific phosphodiesterase-5/PDE6 chimeric proteins and analyzing their localization in rods of transgenic Xenopus laevis. We found that efficient OS localization of chimeric isoprenylated PDE enzymes required the presence of a targeting motif within the PDE6 GAFa domain. Furthermore, the GAFa-dependent localization signal was sufficient to target GAFa fusion protein to the OS. Our results support the idea that effective trafficking of the peripheral membrane proteins to the OS of photoreceptor cells requires a sorting/targeting motif in addition to a membrane-binding signal.
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Pallavi
authors.initials: P
authors.lastname: Cheguru
authors.forename: Zhongming
authors.initials: Z
authors.lastname: Zhang
authors.forename: Nikolai O
authors.initials: NO
authors.lastname: Artemyev
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D015153:Blotting, Western; D003001:Cloning, Molecular; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6 / Q000502:physiology*; D005123:Eye / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007814:Larva; D008099:Liver / Q000166:cytology / Q000378:metabolism; D018613:Microscopy, Confocal; D050506:Mutant Chimeric Proteins / Q000502:physiology; D009154:Mutation / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D017948:Retinal Rod Photoreceptor Cells / Q000187:drug effects / Q000502:physiology; D012374:Rod Cell Outer Segment / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D014982:Xenopus laevis
chemical_list: D050506:Mutant Chimeric Proteins; D010726:Phosphodiesterase Inhibitors; D054707:Cyclic Nucleotide Phosphodiesterases, Type 6
keywords: GAF domain; PDE6; protein trafficking; retina; rods; targeting signal