mtCLIC is up-regulated and maintains a mitochondrial membrane potential in mtDNA-depleted L929 cells.
To explain why mitochondrial DNA (mtDNA)-depleted or rho0 cells still keep a mitochondrial membrane potential (Delta(psi)m) in the absence of respiration, several hypotheses have been proposed. The principal and well accepted one involves a reverse of action for ANT combined to F1-ATPase activity. However, the existence of other putative electrogenic channels has been speculated. Here, using mRNA differential display reverse transcriptase-polymerase chain reaction on L929 mtDNA-depleted cells, we identified mtCLIC as a differentially expressed gene in cells deprived from mitochondrial ATP production. Mitochondrial chloride intracellular channel (mtCLIC), a member of a recently discovered and expanding family of chloride intracellular channels, is up-regulated in mtDNA-depleted and rho0 cells. We showed that its expression is dependent on CREB and p53 and is sensitive to calcium and tumor necrosis factor alpha. Interestingly, up- or down-regulation of mtCLIC protein expression changes Delta(psi)m whereas the chloride channel inhibitor NPPB reduces the Delta(psi)m in mtDNA-depleted L929 cells, measured with the fluorescent probe rhodamine 123. Finally, we demonstrated that purified mitochondria from mtDNA-depleted cells incorporate, in a NPPB-sensitive manner, more 36chloride than parental mitochondria. These findings suggest that mtCLIC could be involved in mitochondrial membrane potential generation in mtDNA-depleted cells, a feature required to prevent apoptosis and to drive continuous protein import into mitochondria.
Arnould
T
T
Laboratoire de Biochimie et Biologie Cellulaire, University of Namur (F.U.N.D.P), 61 rue de Bruxelles, 5000 Namur, Belgium. thierry.arnould@fundp.ac.be
Mercy
L
L
Houbion
A
A
Vankoningsloo
S
S
Renard
P
P
Pascal
T
T
Ninane
N
N
Demazy
C
C
Raes
M
M
D000818:Animals; D002118:Calcium / Q000502:physiology; D002460:Cell Line; D018118:Chloride Channels / Q000096:biosynthesis* / Q000502:physiology*; D017362:Cyclic AMP Response Element-Binding Protein / Q000502:physiology; D004272:DNA, Mitochondrial / Q000235:genetics; D005786:Gene Expression Regulation; D008564:Membrane Potentials; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D024101:Mitochondrial Proteins / Q000096:biosynthesis* / Q000502:physiology*; D008954:Models, Biological; D012333:RNA, Messenger / Q000096:biosynthesis; D015854:Up-Regulation
C479423:CLIC protein, mouse; D018118:Chloride Channels; D017362:Cyclic AMP Response Element-Binding Protein; D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; D012333:RNA, Messenger; D002118:Calcium