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.
Savignan
F
F
Laboratoire de Physiologie et de Physiopathologie de la Signalisation Cellulaire, Université Bordeaux 2, Bordeaux, France.
Ballion
B
B
Odessa
M F
MF
Charveron
M
M
Bordat
P
P
Dufy
B
B
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