Ankyrin-B is required for coordinated expression of beta-2-spectrin, the Na/K-ATPase and the Na/Ca exchanger in the inner segment of rod photoreceptors

Exp Eye Res. 2009 Jan;88(1):57-64. doi: 10.1016/j.exer.2008.09.022. Epub 2008 Nov 1.

Abstract

Rod photoreceptors are highly polarized cells whose exquisite sensitivity to light depends on precise compartmentalization of ion channels/transporters within specialized membrane domains. Here, we report evidence for an ankyrin-B based mechanism for coordinated expression of the beta-2-spectrin-based membrane skeleton, and the Na/K-ATPase and Na/Ca exchanger in the inner segment of rod photoreceptors. We first discovered that ankyrin-B localizes to the inner segments but not outer segments of rod photoreceptors in vertebrates including humans, mice, and frogs. We found that haploinsufficiency of ankyrin-B in mice is accompanied by 50% reduction in inner segments of membrane proteins, including the Na/K-ATPase and the Na/Ca exchanger, as well as beta-2-spectrin, which is a component of the spectrin-actin membrane skeleton. These results are consistent with a mechanism where ankyrin-B is required to restrict the Na/K-ATPase and Na/Ca exchanger to the inner segment of rod photoreceptors by tethering these membrane proteins to beta-2-spectrin.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ankyrins / deficiency
  • Ankyrins / metabolism
  • Ankyrins / physiology*
  • Carrier Proteins / metabolism*
  • Electroretinography
  • Eye Proteins / metabolism
  • Humans
  • Mice
  • Mice, Inbred C57BL
  • Microfilament Proteins / metabolism*
  • Retinal Photoreceptor Cell Inner Segment / metabolism*
  • Retinal Photoreceptor Cell Inner Segment / physiology
  • Sodium-Calcium Exchanger / metabolism*
  • Sodium-Potassium-Exchanging ATPase / metabolism*
  • Species Specificity
  • Xenopus

Substances

  • ANK2 protein, human
  • Ank2 protein, mouse
  • Ankyrins
  • Carrier Proteins
  • Eye Proteins
  • Microfilament Proteins
  • Sodium-Calcium Exchanger
  • fodrin
  • Sodium-Potassium-Exchanging ATPase