The organellular chloride channel protein CLIC4/mtCLIC translocates to the nucleus in response to cellular stress and accelerates apoptosis.
CLIC4/mtCLIC, a chloride intracellular channel protein, localizes to the mitochondria and cytoplasm of keratinocytes and participates in the apoptotic response to stress. We now show that multiple stress inducers cause the translocation of cytoplasmic CLIC4 to the nucleus. Immunogold electron microscopy and confocal analyses indicate that nuclear CLIC4 is detected prior to the apoptotic phenotype. CLIC4 associates with the Ran, NTF2, and Importin-alpha nuclear import complexes in immunoprecipitates of lysates from cells treated with apoptotic/stress-inducing agents. Deletion or mutation of the nuclear localization signal in the C terminus of CLIC4 eliminates nuclear translocation, whereas N terminus deletion enhances nuclear localization. Targeting CLIC4 to the nucleus via adenoviral transduction accelerates apoptosis when compared with cytoplasmic CLIC4, and only nuclear-targeted CLIC4 causes apoptosis in Apaf null mouse fibroblasts or in Bcl-2-overexpressing keratinocytes. These results indicate that CLIC4 nuclear translocation is an integral part of the cellular response to stress and may contribute to the initiation of nuclear alterations that are associated with apoptosis.
Suh
Kwang S
KS
Laboratory of Cellular Carcinogenesis and Tumor Promotion, Center for Cancer Research, NCI, National Institutes of Health (NIH), Bethesda, Maryland 20892, USA.
Mutoh
Michihiro
M
Nagashima
Kunio
K
Fernandez-Salas
Ester
E
Edwards
Lindsay E
LE
Hayes
Daniel D
DD
Crutchley
John M
JM
Marin
Keith G
KG
Dumont
Rebecca A
RA
Levy
Joshua M
JM
Cheng
Christina
C
Garfield
Susan
S
Yuspa
Stuart H
SH
D021581:Active Transport, Cell Nucleus; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D002478:Cells, Cultured; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D051379:Mice; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D019913:Nuclear Localization Signals / Q000235:genetics / Q000378:metabolism; D015388:Organelles / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion
C479423:CLIC protein, mouse; D018118:Chloride Channels; D024101:Mitochondrial Proteins; D019913:Nuclear Localization Signals; D011994:Recombinant Proteins; D004247:DNA