The influence of SRC-family tyrosine kinases on Na,K-ATPase activity in lens epithelium

Invest Ophthalmol Vis Sci. 2005 Feb;46(2):618-22. doi: 10.1167/iovs.04-0809.


Purpose: Na,K-adenosine triphosphatase (ATPase) is essential for the regulation of cytoplasmic ion concentrations in lens cells. Earlier studies demonstrated that tyrosine phosphorylation by Lyn kinase, a Src-family member, inhibits Na,K-ATPase activity in porcine lens epithelium. In the present study, experiments were conducted to compare the ability of other Src-family kinases (Fyn, Src, and Lck) and Fes, a non-Src-family tyrosine kinase, to alter Na,K-ATPase activity.

Methods: Membranes prepared from porcine lens epithelium were incubated with partially purified tyrosine kinases in buffer containing 1 mM adenosine triphosphate (ATP). ATP hydrolysis in the presence and absence of ouabain was used to measure Na,K-ATPase activity. Western blot analysis was used to examine phosphotyrosine-containing proteins and tyrosine kinase expression.

Results: Fyn reduced Na,K-ATPase activity by approximately 30%. In contrast, Src caused a approximately 38% increase of Na,K-ATPase activity. Na,K-ATPase activity in membrane material treated with Lck or Fes was not significantly altered, even though Lck and Fes treatment induced robust tyrosine phosphorylation. Added exogenously, each tyrosine kinase induced a different pattern of membrane protein tyrosine phosphorylation. As judged by immunoprecipitation, Src, Fyn, Lyn, and Lck elicited tyrosine phosphorylation of the Na,K-ATPase alpha1 protein. Src, Fyn, Lyn, Lck, and Fes were each detectable in the epithelium by Western blot.

Conclusions: The results indicate considerable variation in the Na,K-ATPase activity response of lens epithelium to different tyrosine kinases. This could perhaps explain why inhibition of Na,K-ATPase activity is reported to be caused by tyrosine phosphorylation in some tissues, whereas stimulation of Na,K-ATPase activity is observed in other tissues.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphate / pharmacology
  • Animals
  • Blotting, Western
  • Cell Membrane / drug effects
  • Cell Membrane / enzymology
  • Enzyme Inhibitors / pharmacology
  • Epithelium / drug effects
  • Epithelium / enzymology
  • Hydrolysis
  • Lens, Crystalline / drug effects*
  • Lens, Crystalline / enzymology
  • Ouabain / pharmacology
  • Phosphorylation
  • Sodium-Potassium-Exchanging ATPase / metabolism*
  • Swine
  • Tyrosine / metabolism
  • src-Family Kinases / pharmacology*


  • Enzyme Inhibitors
  • Tyrosine
  • Ouabain
  • Adenosine Triphosphate
  • src-Family Kinases
  • Sodium-Potassium-Exchanging ATPase