The influence of Lyn kinase on Na,K-ATPase in porcine lens epithelium.
Na,K-ATPase is essential for the regulation of cytoplasmic Na+ and K+ levels in lens cells. Studies on the intact lens suggest activation of tyrosine kinases may inhibit Na,K-ATPase function. Here, we tested the influence of Lyn kinase, a Src-family member, on tyrosine phosphorylation and Na,K-ATPase activity in membrane material isolated from porcine lens epithelium. Western blot studies indicated the expression of Lyn in lens cells. When membrane material was incubated in ATP-containing solution containing partially purified Lyn kinase, Na,K-ATPase activity was reduced by approximately 38%. Lyn caused tyrosine phosphorylation of multiple protein bands. Immunoprecipitation and Western blot analysis showed Lyn treatment causes an increase in density of a 100-kDa phosphotyrosine band immunopositive for Na,K-ATPase alpha1 polypeptide. Incubation with protein tyrosine phosphatase 1B (PTP-1B) reversed the Lyn-dependent tyrosine phosphorylation increase and the change of Na,K-ATPase activity. The results suggest that Lyn kinase treatment of a lens epithelium membrane preparation is able to bring about partial inhibition of Na,K-ATPase activity associated with tyrosine phosphorylation of multiple membrane proteins, including the Na,K-ATPase alpha1 catalytic subunit.
Bozulic
Larry D
LD
Department of Ophthalmology and Visual Sciences, School of Medicine, University of Louisville, Louisville, KY 40202, USA.
Dean
William L
WL
Delamere
Nicholas A
NA
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D027682:Cation Transport Proteins / Q000037:antagonists & inhibitors; D004848:Epithelium / Q000187:drug effects / Q000201:enzymology; D007527:Isoenzymes / Q000037:antagonists & inhibitors; D007908:Lens, Crystalline / Q000187:drug effects* / Q000201:enzymology*; D008565:Membrane Proteins / Q000037:antagonists & inhibitors; D010766:Phosphorylation / Q000187:drug effects; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013552:Swine; D014443:Tyrosine / Q000378:metabolism; D019061:src-Family Kinases / Q000494:pharmacology*
D027682:Cation Transport Proteins; D007527:Isoenzymes; D008565:Membrane Proteins; D014443:Tyrosine; D000255:Adenosine Triphosphate; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D000251:Adenosine Triphosphatases; C021838:sodium-translocating ATPase; D000254:Sodium-Potassium-Exchanging ATPase