Interleukin-3 withdrawal induces an early increase in mitochondrial membrane potential unrelated to the Bcl-2 family. Roles of intracellular pH, ADP transport, and F(0)F(1)-ATPase.
Cytokines such as interleukin-3 (IL-3) promote the survival of hematopoietic cells through mechanisms that are not well characterized. Withdrawal of IL-3 from an IL-3-dependent pro-B cell line induced early stress-related events that preceded cell death by more than 40 h. Intracellular pH rose above pH 7.8, peaking 2-3 h post-IL-3 withdrawal, and induced a transient increase in mitochondrial membrane potential (Delta Psi(m)) detected using several different dyes. Similar events were observed following IL-7 withdrawal from a different dependent cell line. Bcl-2, Bax, and caspases were unrelated to these early events. Intracellular alkaline pH inhibited the mitochondrial import of ADP, which would limit ATP synthesis. Total cellular ATP sharply declined during this early period, presumably as a consequence of suppressed ADP import. This was followed by an increase in reduced pyridine nucleotides. The transient increase in Delta Psi(m) was blocked by oligomycin, an inhibitor of F(0)F(1-)ATPase that may have undergone reversal caused by the abnormal ADP-ATP balance within mitochondria. These findings suggest a novel sequence of early events following trophic factor withdrawal in which alkaline pH inhibits ADP import into mitochondria, reversing the F(0)F(1-)ATPase, which in turn consumes ATP and pumps out protons, raising Delta Psi(m).
Khaled
A R
AR
Laboratory of Molecular Immunoregulation, Division of Basic Sciences, NCI, National Institutes of Health, Frederick, Maryland 21702, USA.
Reynolds
D A
DA
Young
H A
HA
Thompson
C B
CB
Muegge
K
K
Durum
S K
SK
D000244:Adenosine Diphosphate / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D001692:Biological Transport; D020169:Caspases / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D007377:Interleukin-3 / Q000502:physiology*; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000502:physiology*; D009243:NAD / Q000032:analysis / Q000378:metabolism; D010084:Oxidation-Reduction; D011518:Proto-Oncogene Proteins / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000502:physiology*; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; D007377:Interleukin-3; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D009243:NAD; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D020169:Caspases; D006180:Proton-Translocating ATPases