Carbonic anhydrase IX interacts with bicarbonate transporters in lamellipodia and increases cell migration via its catalytic domain

J Biol Chem. 2012 Jan 27;287(5):3392-402. doi: 10.1074/jbc.M111.286062. Epub 2011 Dec 14.

Abstract

Carbonic anhydrase IX (CA IX) is a hypoxia-induced cell surface enzyme expressed in solid tumors, and functionally involved in acidification of extracellular pH and destabilization of intercellular contacts. Since both extracellular acidosis and reduced cell adhesion facilitate invasion and metastasis, we investigated the role of CA IX in cell migration, which promotes the metastatic cascade. As demonstrated here, ectopically expressed CA IX increases scattering, wound healing and transwell migration of MDCK cells, while an inactive CA IX variant lacking the catalytic domain (ΔCA) fails to do so. Correspondingly, hypoxic HeLa cells exhibit diminished migration upon inactivation of the endogenous CA IX either by forced expression of the dominant-negative ΔCA variant or by treatment with CA inhibitor, implying that the catalytic activity is indispensable for the CA IX function. Interestingly, CA IX improves cell migration both in the absence and presence of hepatocyte growth factor (HGF), an established inducer of epithelial-mesenchymal transition. On the other hand, HGF up-regulates CA IX transcription and triggers CA IX protein accumulation at the leading edge of lamellipodia. In these membrane regions CA IX co-localizes with sodium bicarbonate co-transporter (NBCe1) and anion exchanger 2 (AE2) that are both components of the migration apparatus and form bicarbonate transport metabolon with CA IX. Moreover, CA IX physically interacts with AE2 and NBCe1 in situ, as shown here for the first time. Thus, our findings suggest that CA IX actively contributes to cell migration via its ability to facilitate ion transport and pH control at protruding fronts of moving cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anion Transport Proteins / genetics
  • Anion Transport Proteins / metabolism*
  • Antigens, Neoplasm / biosynthesis*
  • Antigens, Neoplasm / genetics
  • Antiporters / genetics
  • Antiporters / metabolism*
  • Bicarbonates / metabolism
  • Carbonic Anhydrase IX
  • Carbonic Anhydrases / biosynthesis*
  • Carbonic Anhydrases / genetics
  • Cell Hypoxia / physiology
  • Cell Movement / physiology*
  • Gene Expression Regulation, Enzymologic / physiology*
  • HeLa Cells
  • Hepatocyte Growth Factor / genetics
  • Hepatocyte Growth Factor / metabolism
  • Humans
  • Hydrogen-Ion Concentration
  • Ion Transport / physiology
  • Protein Structure, Tertiary
  • Pseudopodia / genetics
  • Pseudopodia / metabolism*
  • SLC4A Proteins
  • Sodium-Bicarbonate Symporters / genetics
  • Sodium-Bicarbonate Symporters / metabolism*
  • Up-Regulation / physiology

Substances

  • Anion Transport Proteins
  • Antigens, Neoplasm
  • Antiporters
  • Bicarbonates
  • HGF protein, human
  • SLC4A Proteins
  • SLC4A4 protein, human
  • Sodium-Bicarbonate Symporters
  • Hepatocyte Growth Factor
  • CA9 protein, human
  • Carbonic Anhydrase IX
  • Carbonic Anhydrases