Mitochondrial membrane potential (DeltaPsi) and Ca(2+)-induced differentiation in HaCaT keratinocytes.
We have used the human calcium- and temperature-dependent (HaCaT) keratinocyte cell line to elucidate mechanisms of switching from a proliferating to a differentiating state. When grown in low calcium medium (<0.1 mM) HaCaT cells proliferate. However, an increase in the calcium concentration of the culture medium, [Ca(2+)](0), induces growth arrest and the cells start to differentiate. Numerous studies have already shown that the increase in [Ca(2+)](0) results in acute and sustained increases in intracellular calcium concentration, [Ca(2+)](i). We find that the Ca(2+)-induced cell differentiation of HaCaT cells is also accompanied by a significant decrease in mitochondrial membrane potential, DeltaPsi. By combining patch-clamp electrophysiological recordings and microspectrofluorimetric measurements of DeltaPsi on single cells, we show that the increase in [Ca(2+)](i) led to DeltaPsi depolarization. In addition, we report that tetraethylammonium (TEA), a blocker of plasma membrane K(+) channels, which is known to inhibit cell proliferation, and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), a blocker of plasma membrane Cl(-) channels, also affect DeltaPsi. Both these agents stimulate HaCaT cell differentiation. These data therefore strongly suggest a direct causal relationship between depolarization of DeltaPsi and the inhibition of proliferation and induction of differentiation in HaCaT keratinocytes.
Laboratoire de Physiologie et de Physiopathologie de la Signalisation Cellulaire, Université Bordeaux 2, Bordeaux, France.
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F
Savignan
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Ballion
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Odessa
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Charveron
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Bordat
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Dufy
D002118:Calcium / Q000494:pharmacology*; D002122:Calcium Chloride / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects*; D002455:Cell Division; D002460:Cell Line; D004533:Egtazic Acid / Q000031:analogs & derivatives*; D006801:Humans; D007150:Immunohistochemistry; D008564:Membrane Potentials / Q000502:physiology*; D008928:Mitochondria / Q000502:physiology*
C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D004533:Egtazic Acid; D002122:Calcium Chloride; D002118:Calcium