title: c-Jun NH2-terminal kinase (JNK)-dependent nuclear translocation of apoptosis-inducing factor (AIF) following engagement of membrane immunoglobulin on WEHI-231 B lymphoma cells.
abstract: WEHI-231 B lymphoma cells have been employed for analysis of antigen-induced B cell unresponsiveness because these cells undergo cell cycle arrest in G1, accompanied by induction of apoptosis. In the present study, we examined the requirement for toxic small molecules apoptosis-inducing factor (AIF) and cytochrome c, and subsequent caspase activation in apoptotic cell death in WEHI-231 and CH31 B lymphoma cells following engagement of membrane immunoglobulin (mIg). Pan-caspase inhibitor BD-fmk blocked mIg-mediated increase in cells with sub-G1 DNA content, whereas it did not affect mIg-mediated loss of mitochondrial membrane potential and phosphatidylserine exposure on B cell membrane. Dominant-negative form of c-Jun NH2-terminal kinase1 (JNK1) blocked the translocation of AIF into the nuclei and cytosol from the mitochondria in the WEHI-231 and CH31 cells following mIg engagement, whereas constitutively active form of JNK1 enhanced it. This AIF translocation was also blocked by Bcl-xL, but not by BD-fmk. Moreover, AIF-deficient clones via small interfering RNA (siRNA)-mediated method showed small increase in loss of mitochondrial membrane potential. After mIg engagement, the AIF-deficient clones displayed an enhanced sensitivity to mIg-mediated apoptosis, concomitant with translocation of a residual AIF into the nuclei, compared with control clone. Our findings are compatible with the notion that AIF has dual role, with a proapoptotic function in the nuclei and a distinct anti-apoptotic function in the mitochondria. These observations would be valuable for analysis of B cell unresponsiveness and hopefully for treatment of diseases involving B cell dysfunction.
authors.affiliation: Department of Immunology, Intractable Immune System Disease Research Center, Tokyo Medical University, 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan.
authors.forename: Eiko
authors.initials: E
authors.lastname: Takada
authors.forename: Kikumi
authors.initials: K
authors.lastname: Hata
authors.forename: Junichiro
authors.initials: J
authors.lastname: Mizuguchi
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D051033:Apoptosis Inducing Factor / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism*; D002999:Clone Cells; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016193:G1 Phase / Q000187:drug effects; D007075:Immunoglobulin M / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008223:Lymphoma / Q000201:enzymology* / Q000473:pathology*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D034622:RNA Interference; D051020:bcl-X Protein / Q000378:metabolism
chemical_list: D000906:Antibodies; D051033:Apoptosis Inducing Factor; D004791:Enzyme Inhibitors; D007075:Immunoglobulin M; D010718:Phosphatidylserines; D051020:bcl-X Protein; D004247:DNA; D048031:JNK Mitogen-Activated Protein Kinases