Smad3 potentiates transforming growth factor beta (TGFbeta )-induced apoptosis and expression of the BH3-only protein Bim in WEHI 231 B lymphocytes.
Transforming growth factor-beta (TGFbeta) is a potent growth inhibitor and inducer of apoptosis in B lymphocytes and is essential for immune regulation and maintenance of self-tolerance. Here we show that exogenous overexpression of Smad3 potentiates TGFbeta-induced apoptosis and expression of the pro-apoptotic protein Bim in WEHI 231 B lymphocytes. Overexpression of dominant-negative forms of Smad3 abrogate these TGFbeta-induced responses. We also demonstrate that TGFbeta induces Bim protein expression concomitant with its induction of apoptosis in the mouse progenitor B lymphocyte cell line, Ba/F3. Enhanced expression of Bim protein induced by TGFbeta is associated with an increased association of Bim with Bcl-2 and a concomitant loss of mitochondrial membrane potential. Furthermore, we find that the anti-apoptotic effect of the pro-survival cytokine CD40 results in the abrogation of TGFbeta-mediated Bim induction. Our data provide the first evidence of Bim expression levels that are increased by the addition of a pro-apoptotic cytokine, TGFbeta, and also suggest that the TGFbeta-specific transcription factor Smad3 plays a role in mediating Bim expression levels and apoptosis.
Wildey
Gary M
GM
Department of Cell Biology, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA.
Patil
Supriya
S
Howe
Philip H
PH
D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; D015152:Blotting, Northern; D015153:Blotting, Western; D019013:CD40 Antigens / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism*; D002455:Cell Division; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D016207:Cytokines / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology*; D019281:Dimerization; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005799:Genes, Dominant; D008564:Membrane Potentials; D008565:Membrane Proteins; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051900:Smad3 Protein; D013997:Time Factors; D015534:Trans-Activators / Q000502:physiology*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D019013:CD40 Antigens; D002352:Carrier Proteins; D016207:Cytokines; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D012313:RNA