Activation of a Ca2+-permeable cation channel by two different inducers of apoptosis in a human prostatic cancer cell line.
1. We have combined patch clamp recording with simultaneous [Ca2+]i measurements in single LNCaP cells (a human prostate cancer cell line), to study the activation of Ca2+-permeable channels by two different inducers of apoptosis, ionomycin and serum deprivation. 2. In perforated patch recording, LNCaP cells had a membrane potential of -40 mV and a resting [Ca2+]i of 90 nM. Application of ionomycin at levels that induced apoptosis in these cells (10 microM) produced a biphasic increase in [Ca2+]i. The first rise in [Ca2+]i was due to release of Ca2+ from internal stores and it was associated with a membrane hyperpolarization to -77 mV. The latter was probably due to the activation of high conductance, Ca2+- and voltage-dependent K+ channels (maxi-K). Conversely, the second rise in [Ca2+]i was always preceded by and strictly associated with membrane depolarization and required external Ca2+. Serum deprivation, another inducer of apoptosis, unmasked a voltage-independent Ca2+ permeability as well. 3. A lower concentration of ionomycin (1 microM) did not induce apoptosis, and neither depolarized LNCaP cells nor produced the biphasic increase in [Ca2+]i. However, the first increment in [Ca2+]i due to release from internal Ca2+ stores was evident at this concentration of ionomycin. 4. Simultaneous recordings of [Ca2+]i and ion channel activity in the cell attached configuration of patch clamp revealed a Ca2+-permeable, Ca2+-independent, non-selective cation channel of 23 pS conductance. This channel was activated only during the second increment in [Ca2+]i induced by ionomycin. The absence of serum activated the 23 pS channel as well, albeit at a lower frequency than with ionomycin. 5. Thus, the 23 pS channel can be activated by two unrelated inducers of apoptosis and it could be another Ca2+ influx mechanism in programmed cell death of LNCaP cells.
Gutierrez
A A
AA
Departamento de Bioquímica, Instituto de Fisiología Celular, Universidad Nacional Autonoma de Mexico, Mexico DF 04510, Mexico.
Arias
J M
JM
García
L
L
Mas-Oliva
J
J
Guerrero-Hernández
A
A
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D016895:Culture Media, Serum-Free; D006801:Humans; D007473:Ion Channels / Q000187:drug effects* / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D015759:Ionomycin / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D011471:Prostatic Neoplasms / Q000378:metabolism / Q000473:pathology; D014407:Tumor Cells, Cultured
D016895:Culture Media, Serum-Free; D007473:Ion Channels; D015759:Ionomycin; D002118:Calcium