FXYD5 Protein Has a Pro-inflammatory Role in Epithelial Cells

J Biol Chem. 2016 May 20;291(21):11072-82. doi: 10.1074/jbc.M115.699041. Epub 2016 Mar 22.

Abstract

The FXYD proteins are a family of small membrane proteins that share an invariant four amino acid signature motif F-X-Y-D and act as tissue-specific regulatory subunits of the Na,K-ATPase. FXYD5 (also termed dysadherin or RIC) is a structurally and functionally unique member of the FXYD family. As other FXYD proteins, FXYD5 specifically interacts with the Na,K-ATPase and alters its kinetics by increasing Vmax However, unlike other family members FXYD5 appears to have additional functions, which cannot be readily explained by modulation of transport kinetics. Knockdown of FXYD5 in MDA-MB-231 breast cancer cells largely decreases expression and secretion of the chemokine CCL2 (MCP-1). A related effect has also been observed in renal cell carcinoma cells. The current study aims to further characterize the relationship between the expression of FXYD5 and CCL2 secretion. We demonstrate that transfection of M1 epithelial cell line with FXYD5 largely increases lipopolysaccharide (LPS) stimulated CCL2 mRNA and secretion of the translated protein. We have completed a detailed analysis of the molecular events leading to the above response. Our key findings indicate that FXYD5 generates a late response by increasing the surface expression of the TNFα receptor, without affecting its total protein level, or mRNA transcription. LPS administration to mice demonstrates induced secretion of CCL2 and TNFα in FXYD5-expressing lung peripheral tissue, which suggests a possible role for FXYD5 in normal epithelia during inflammation.

Keywords: cytokine induction; inflammation; lipopolysaccharide (LPS); plasma membrane; translocation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cell Line, Tumor
  • Chemokine CCL2 / genetics
  • Chemokine CCL2 / metabolism
  • Epithelial Cells / metabolism
  • Gene Expression / drug effects
  • Gene Knockdown Techniques
  • Humans
  • Inflammation Mediators / metabolism
  • Kinetics
  • Lipopolysaccharides / pharmacology
  • Membrane Glycoproteins / antagonists & inhibitors
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism*
  • Mice
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Receptors, Tumor Necrosis Factor / genetics
  • Receptors, Tumor Necrosis Factor / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Signal Transduction / drug effects

Substances

  • CCL2 protein, human
  • Ccl2 protein, mouse
  • Chemokine CCL2
  • FXYD5 protein, human
  • FXYD5 protein, mouse
  • Inflammation Mediators
  • Lipopolysaccharides
  • Membrane Glycoproteins
  • Membrane Proteins
  • Neoplasm Proteins
  • RNA, Messenger
  • Receptors, Tumor Necrosis Factor
  • Recombinant Proteins