Purchase this article with an account.
Sheila A Baker, Joseph Laird, Colten K Lankford, David M Yamaguchi, Yuan Pan; Investigating 14-3-3 as a coordinator for the assembly and trafficking of HCN1 in photoreceptors. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4803.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Photoreceptor signaling depends on the coordinated action of multiple ion transporters and channels. Photoreceptor outer segments, inner segments, and synapses all contain a unique inventory of ion channels. How various ion channels are sorted into the correct compartment is completely unknown. In this study we have investigated the mechanisms controlling the trafficking of a representative inner segment localized channel – HCN1. HCN1 opens in response to hyperpolarization and carries a feedback current that shapes visual responses under medium and bright light conditions.
Trafficking signals were mapped by analyzing the subcellular localization of a series of HCN1 mutants expressed in transgenic Xenopus rods. Trafficking mutants were verified in mammalian HCN1 expressed in cell culture using imaging, immunoprecipitation, and velocity sedimentation assays.
Two trafficking signals with opposing functions were identified – a di-arginine endoplasmic reticulum (ER) retention signal and a novel ER export signal. The export signal dominates over the retention signal but when the retention signal is mutated there is an increase in unassembled HCN1 monomers. Binding motifs for the ubiquitous 14-3-3 family of signaling adaptors flank both ER trafficking signals. 14-3-3 binding to HCN1 was validated and found to be phosphorylation dependent.
HCN1 encodes for two trafficking signals that regulate trafficking out of the ER, and HCN1 has been identified as a novel client for 14-3-3. We suggest that recruitment of 14-3-3 to HCN1 tetramers blocks the action of the ER retention signal thereby promoting forward trafficking of intact channels. This model places 14-3-3 in a key regulatory position where it coordinates the action of the two opposing trafficking signals in a quality control checkpoint for the trafficking of HCN1.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
This PDF is available to Subscribers Only