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Amiloride inhibits macropinocytosis by lowering submembranous pH and preventing Rac1 and Cdc42 signaling.

Macropinocytosis is differentiated from other types of endocytosis by its unique susceptibility to inhibitors of Na(+)/H(+) exchange. Yet, the functional relationship between Na(+)/H(+) exchange and macropinosome formation remains obscure. In A431 cells, stimulation by EGF simultaneously activated macropinocytosis and Na(+)/H(+) exchange, elevating cytosolic pH and stimulating Na(+) influx. Remarkably, although inhibition of Na(+)/H(+) exchange by amiloride or HOE-694 obliterated macropinocytosis, neither cytosolic alkalinization nor Na(+) influx were required. Instead, using novel probes of submembranous pH, we detected the accumulation of metabolically generated acid at sites of macropinocytosis, an effect counteracted by Na(+)/H(+) exchange and greatly magnified when amiloride or HOE-694 were present. The acidification observed in the presence of the inhibitors did not alter receptor engagement or phosphorylation, nor did it significantly depress phosphatidylinositol-3-kinase stimulation. However, activation of the GTPases that promote actin remodelling was found to be exquisitely sensitive to the submembranous pH. This sensitivity confers to macropinocytosis its unique susceptibility to inhibitors of Na(+)/H(+) exchange.

Pubmed ID: 20156964


  • Koivusalo M
  • Welch C
  • Hayashi H
  • Scott CC
  • Kim M
  • Alexander T
  • Touret N
  • Hahn KM
  • Grinstein S


The Journal of cell biology

Publication Data

February 22, 2010

Associated Grants

  • Agency: NHLBI NIH HHS, Id: F30HL094020-02
  • Agency: NIGMS NIH HHS, Id: GM57464
  • Agency: NIGMS NIH HHS, Id: GM64346
  • Agency: Canadian Institutes of Health Research, Id: MOP4665
  • Agency: NIGMS NIH HHS, Id: R01 GM057464
  • Agency: NIGMS NIH HHS, Id: T32 GM008719
  • Agency: NIGMS NIH HHS, Id: U54 GM064346

Mesh Terms

  • Actin Depolymerizing Factors
  • Amiloride
  • Animals
  • Cell Line
  • Cytosol
  • Enzyme Activation
  • Epidermal Growth Factor
  • GRB2 Adaptor Protein
  • Guanidines
  • Humans
  • Hydrogen-Ion Concentration
  • Hydrolysis
  • Intracellular Membranes
  • Phosphorylation
  • Pinocytosis
  • Proto-Oncogene Proteins c-akt
  • Rabbits
  • Recombinant Fusion Proteins
  • Signal Transduction
  • Sodium
  • Sodium-Hydrogen Antiporter
  • Sulfones
  • cdc42 GTP-Binding Protein
  • rac1 GTP-Binding Protein