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

Abstract：

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.

journal_name

Invest Ophthalmol Vis Sci

journal_title

Investigative ophthalmology & visual science

authors

Bozulic LD,Dean WL,Delamere NA

doi

10.1167/iovs.04-0809

keywords:

subject

Has Abstract

pub_date

2005-02-01 00:00:00

pages

618-22

issue

eissn

0146-0404

issn

1552-5783

pii

46/2/618

journal_volume

pub_type

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