Intracellular calcium oscillations in cell populations of ras-transfected I-7 subline of human HaCaT keratinocytes.
We have observed oscillations of intracellular Ca2+ (Ca[i]) concentration in populations of ras-transfected HaCaT keratinocytes of I-7 subline. In postconfluent monolayers of I-7 keratinocytes, an increase in extracellular Ca2+ (Ca[o]) concentration to 0.25-0.5 mM induced sinusoidal Ca(i) oscillations, which persisted longer than 1 h with amplitudes of 50-150 nM and periods of 5-10 min. Thapsigargin, which depletes internal Ca2+ stores, did not prevent Ca(o)-induced Ca(i) oscillations, and it also induced Ca(i) oscillations in the ras-transfected I-7 line. Removal of extracellular Ca2+ or addition of Ca2+-entry blocker La3+ or SK&F 96365 inhibited Ca(i) oscillations, suggesting that Ca(i) oscillations in ras-transfected HaCaT keratinocytes were dependent on Ca2+ influx across the plasma membrane. Because the Ca(o)-induced Ca(i) oscillations have been observed only in ras-transfected I-7 subline and not in its nontransfected parental HaCaT line, this may provide a partial explanation for the divergent responses of ras-transfected and nontransfected keratinocytes to Ca(o) signal for control of growth and differentiation.
Shi
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Department of Dermatology, University of California Davis School of Medicine, 95616, USA.
Isseroff
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D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D011905:Genes, ras; D006801:Humans; D015603:Keratinocytes / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014162:Transfection
D019284:Thapsigargin; D002118:Calcium