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Forschungsdatenbank PMU-SQQUID

Activation of Na+/H(+)-exchanger by transforming Ha-ras requires stimulated cellular calcium influx and is associated with rearrangement of the actin cytoskeleton.
Ritter, M; Wöll, E; Haller, T; Dartsch, PC; Zwierzina, H; Lang, F;
Eur J Cell Biol. 1997; 72(3): 222-228.
Originalarbeiten (Zeitschrift)


Ritter Markus


Expression of the Ha-ras oncogene in NIH 3T3 fibroblasts (+ras cells) results in growth factor-independent proliferation and marked alteration of cytoskeletal architecture including breakdown of actin stress fiber network. Compared to identical cells not expressing the oncogene (-ras cells), +ras cells exhibit a more alkaline intracellular pH (pH(i)) and a larger cell volume (CV), both of which are important mitogenic elements. They are due to a set point shift for activation of the Na+/H+-exchanger. Moreover +ras cells respond to stimuli like 0.5% fetal calf serum or bradykinin with sustained oscillations of the cell membrane potential (PD) due to stimulated Ca2+ entry which triggers pulsatile release of calcium from internal stores and subsequent activation of calcium-sensitive K+ channels, 10 mu mol/l bepridil inhibit oscillations of PD and protect +ras cells against actin stress fiber depolymerization, It is shown that bepridil blocks both cellular calcium entry as measured by Mn2+ quenching of fura-2 fluorescence and activation of the Na+/H+-exchanger following expression of the Ha-ras oncogene. Inhibition of the Na+/H+-exchanger with 10 mu mol/l HOE 694, on the other hand, does not significantly alter Ha-ras stimulated calcium entry or cytoskeletal rearrangement. In -ras cells ionomycin (0.1 mu mol/l) leads to a transient increase in Ca-i. This effect is paralleled by a transient depolymerization of actin stress fiber network which cannot be inhibited by HOE 694. Disruption of the actin cytoskeleton in -ras cells by cytochalasin D does not alter steady state cell volume or Na+/H+-exchange activity. However, stimulation of cytochalasin-treated las cells with bradykinin leads to cell swelling which ran be blunted by HOE 694. The results show that both cytoskeletal rearrangement and activation of the Na+/H+-exchanger following expression of the Ha-ras oncogene require stimulated calcium influx and Ca-i oscillations. The depolymerization of the actin cytoskeleton is permissive for the Na+/H+-exchanger to cause cell swelling upon stimulation with bradykinin.

Useful keywords (using NLM MeSH Indexing)

3T3 Cells





Cell Size/drug effects


Enzyme Activation

Hydrogen-Ion Concentration


Oncogene Protein p21(ras)/metabolism*

Sodium-Hydrogen Antiporter/metabolism*

Find related publications in this database (Keywords)

Ha-ras oncogene
calcium channels
intracellular calcium
intracellular pH
cell volume