R. Skryma et al., Store depletion and store-operated Ca2+ current in human prostate cancer LNCaP cells: involvement in apoptosis, J PHYSL LON, 527(1), 2000, pp. 71-83
1. In the present study, we investigated the mechanisms involved in the ind
uction of apoptosis by the Ca2+-ATPase inhibitor thapsigargin (TG), in andr
ogen-sensitive human prostate cancer LNCaP cells.
2. Exposure of fura-2-loaded LNCaP cells to TG in the presence of extracell
ular calcium produced an increase in intracellular Ca2+, the first phase of
which was associated with depletion of intracellular stores and the second
one with consecutive extracellular Ca2+ entry through plasma membrane, sto
re-operated Ca2+ channels (SOCs).
3. For the first time we have identified and characterized the SOC-mediated
membrane current (I-store) in prostate cells using whole-cell, cell-attach
ed, and perforated patch-clamp techniques, combined with fura-2 microspectr
ofluorimetric and Ca2+-imaging measurements.
4. I-store in LNCaP cells lacked voltage-dependent gating and displayed an
inwardly rectifying current-voltage relationship. The unitary conductance o
f SOCs with 80 mM Ca2+ as a charge carrier was estimated at 3.2 +/- 0.4 pS.
The channel has a high selectivity for Ca2+ over monovalent cations and is
inhibited by Ni2+ (0.5-3 mM) and La3+ (1 mu M).
5. Treatment of LNCaP cells with TG (0.1 mu M) induced apoptosis as judged
from morphological changes. Decreasing extracellular free Ca2+ to 200 nM or
adding 0.5 mM Ni2+ enhanced TG-induced apoptosis.
6. The ability of TG to induce apoptosis was not reduced by loading the cel
ls with intracellular Ca2+ chelator (BAPTB-AM). 7. These results indicate t
hat in androgen-sensitive prostate cancer cells the depletion of intracellu
lar Ca2+ stores may trigger apoptosis but that there is no requirement for
the activation of store-activated Ca2+ current and sustained Ca2+ entry in
induction and development of programmed cell death.