September 2016
Volume 57, Issue 12
Open Access
ARVO Annual Meeting Abstract  |   September 2016
Investigating 14-3-3 as a coordinator for the assembly and trafficking of HCN1 in photoreceptors
Author Affiliations & Notes
  • Sheila A Baker
    Biochemistry, Carver College of Med, Univ of Iowa, Iowa City, Iowa, United States
  • Joseph Laird
    Biochemistry, Carver College of Med, Univ of Iowa, Iowa City, Iowa, United States
  • Colten K Lankford
    Biochemistry, Carver College of Med, Univ of Iowa, Iowa City, Iowa, United States
  • David M Yamaguchi
    Biochemistry, Carver College of Med, Univ of Iowa, Iowa City, Iowa, United States
  • Yuan Pan
    Biochemistry, Carver College of Med, Univ of Iowa, Iowa City, Iowa, United States
  • Footnotes
    Commercial Relationships   Sheila Baker, None; Joseph Laird, None; Colten Lankford, None; David Yamaguchi, None; Yuan Pan, None
  • Footnotes
    Support  NIH Grant EY020542
Investigative Ophthalmology & Visual Science September 2016, Vol.57, 4803. doi:
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    • Get Citation

      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.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : 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.

Methods : 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.

Results : 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.

Conclusions : 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.

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