EphB2 and ephrin-B2 regulate the ionic homeostasis of vestibular endolymph

Christopher Dravis, Tao Wu, Michael J. Chumley, Nobuhiko Yokoyama, Shiniu Wei, Doris K. Wu, Daniel C. Marcus, Mark Henkemeyer

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

The ability to transport cations and anions across epithelia is critical for the regulation of pH, ionic homeostasis, and volume of extracellular fluids. Although the transporters and channels that facilitate ion and water movement across cell membranes are well known, the molecular mechanisms and signal transduction events that regulate these activities remain poorly understood. The Eph family of receptor tyrosine kinases and their membrane-anchored ephrin ligands are well known to transduce bidirectional signals that control axon guidance and other cell migration/adhesion events during development. However, these molecules are also expressed in non-motile epithelial cells, including EphB2 in K+-secreting vestibular dark cells and ephrin-B2 in the adjacent transitional cells of the inner ear. Consistent with these expression patterns, mice with cytoplasmic domain mutations that interfere with EphB2 forward signaling or ephrin-B2 reverse signaling exhibit a hyperactive circling (waltzing) locomotion associated with a decreased amount of endolymph fluid that normally fills the vestibular labyrinth. Endolymph is unusual as an extracellular fluid in that it is normally high in K+ and low in Na+. Direct measurement of this fluid in live animals revealed significant decreases in K+ concentration and endolymphatic potential in both EphB2 and ephrin-B2 mutant mice. Our findings provide evidence that bidirectional signaling mediated by B-subclass Ephs and ephrins controls the production and ionic homeostasis of endolymph fluid and thereby provide the first evidence that these molecules can control the activities of mature epithelial cells.

Original languageEnglish (US)
Pages (from-to)93-104
Number of pages12
JournalHearing Research
Volume223
Issue number1-2
DOIs
StatePublished - Jan 1 2007

Keywords

  • Dark cells
  • Endolymph
  • EphB2
  • Ephrin-B2
  • Ionic homeostasis
  • Potassium
  • Receptor tyrosine kinase
  • Transitional cells
  • Vestibular epithelium

ASJC Scopus subject areas

  • Sensory Systems

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    Dravis, C., Wu, T., Chumley, M. J., Yokoyama, N., Wei, S., Wu, D. K., Marcus, D. C., & Henkemeyer, M. (2007). EphB2 and ephrin-B2 regulate the ionic homeostasis of vestibular endolymph. Hearing Research, 223(1-2), 93-104. https://doi.org/10.1016/j.heares.2006.10.007