June 2015
Volume 56, Issue 7
Free
ARVO Annual Meeting Abstract  |   June 2015
Identifying targeting motifs necessary for the differential localization of Na+/K+-ATPase isoforms in photoreceptors
Author Affiliations & Notes
  • Joseph G. Laird
    Biochemistry, University of Iowa, Carver College of Medicine, Iowa City, IA
  • Yuan Pan
    Biochemistry, University of Iowa, Carver College of Medicine, Iowa City, IA
  • David Yamaguchi
    Biochemistry, University of Iowa, Carver College of Medicine, Iowa City, IA
  • Sheila A Baker
    Biochemistry, University of Iowa, Carver College of Medicine, Iowa City, IA
  • Footnotes
    Commercial Relationships Joseph Laird, None; Yuan Pan, None; David Yamaguchi, None; Sheila Baker, None
  • Footnotes
    Support None
Investigative Ophthalmology & Visual Science June 2015, Vol.56, 453. doi:
  • Views
  • Share
  • Tools
    • Alerts
      ×
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      Joseph G. Laird, Yuan Pan, David Yamaguchi, Sheila A Baker; Identifying targeting motifs necessary for the differential localization of Na+/K+-ATPase isoforms in photoreceptors. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):453.

      Download citation file:


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

      ×
  • Supplements
Abstract

Purpose: Na+/K+-ATPase (NKA) is the sodium pump used by all cells to establish and maintain electrochemical gradients across cellular membranes. It can alternatively function in signaling as a receptor for cardiotonic steroids or participate in maintaining cell-cell adhesion. Ways to accommodate the unique requirements of different cell types include the utilization of different NKA isoforms or altering the subcellular localization of NKA. In photoreceptors, NKA composed of the α3 subunit is located in the plasma membrane of the inner segment. But in sperm, NKA is composed of the α4 subunit and localizes to the flagella. We observed that upon expression in photoreceptors NKA α4 localized to the analogous ciliary compartment, the outer segment. Our goal in this study was to take advantage of that observation to dissect the differential targeting information encoded within each of these NKA isoforms.

Methods: A series of GFP-tagged NKA constructs were cloned. These included a series of α3/α4 chimeras, deletion mutants and point mutants of each isoform. The proteins were expressed in Xenopus laevis rods by generating transgenic tadpoles. Retinas from stage 43-46 animals were immunostained with anti-GFP antibodies and imaged with confocal microscopy.

Results: NKA α3 and α4 are most divergent in their cytoplasmic, unstructured N-termini. Chimeras with this region exchanged resulted in changing the localization of α3 from the inner segment plasma membrane to the outer segment and vice versa. Analysis of a series of paired chimeric constructs narrowed the region containing the motif responsible for this differential targeting to fourteen amino acids. Within this region we identified a valine and proline necessary for outer segment localization.

Conclusions: This study allowed us to uncover a targeting motif within a flagellar NKA isoform with similarity to the targeting motif of rhodopsin. We speculate that lack of this targeting motif in NKA α3 contributes to its inner segment localization where competition for energy resources between NKA, phototransduction in the outer segment, and the synaptic vesicle cycle in the synapse can be minimized.

×
×

This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.

×