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Binding of Src to Na+/K+-ATPase forms a functional signaling complex

Jiang Tian1, Ting Cai, Zhaokan Yuan

  • 1Department of Pharmacology, Medical University of Ohio, Toledo, OH 43614, USA.

Molecular Biology of the Cell
|November 4, 2005
PubMed

Insights

Ouabain triggers a functional signaling complex between Na+/K+-ATPase and Src kinase. This interaction regulates Src activity and downstream tyrosine phosphorylation, revealing a novel signal transduction pathway.

Area of Science:

  • Cellular signaling
  • Biochemistry
  • Molecular biology

Background:

  • Ouabain is known to activate Src, leading to tyrosine phosphorylation of downstream effectors.
  • The precise molecular mechanisms underlying this activation, particularly the interaction between Na+/K+-ATPase and Src, remain incompletely understood.

Purpose of the Study:

  • To investigate the formation of a functional signaling complex between Na+/K+-ATPase and Src.
  • To elucidate the nature of the interaction between these two proteins and its regulation by ouabain.

Main Methods:

  • Colocalization studies in LLC-PK1 cells.
  • Fluorescence resonance energy transfer (FRET) analysis to assess protein proximity.
  • GST pulldown assays to determine direct interactions.
  • In vitro kinase assays with purified proteins and cell-based assays.

Main Results:

  • Na+/K+-ATPase and Src colocalize and interact in the plasma membrane, with ouabain regulating the interaction.
  • Src's kinase domain interaction with Na+/K+-ATPase subunit 1 is ouabain-dependent, while SH3SH2 domain binding is constitutive.
  • Binding inhibits Src activity; ouabain releases the kinase domain, restoring activity.
  • Ouabain treatment increases the distance between Na+/K+-ATPase and Src in cells, stimulating tyrosine phosphorylation.

Conclusions:

  • Na+/K+-ATPase and Src form a functional signaling complex regulated by ouabain.
  • This interaction represents a novel mechanism for signal transduction involving a P-type ATPase and a nonreceptor tyrosine kinase.
  • The findings provide new insights into the regulation of Src activity and downstream signaling pathways.

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