The C-terminus of interferon gamma receptor beta chain (IFNgammaR2) has antiapoptotic activity as a Bax inhibitor.
Bax is a pro-apoptotic protein that mediates intrinsic cell-death signaling. Using a yeast-based functional screening approach, we identified interferon gamma receptor beta chain (IFNgammaR2) as a new Bax suppressor. IFNgammaR2 is a component of the IFNgamma receptor complex along with the IFNgammaR alpha chain (IFNgammaR1). Upon IFNgamma binding, a conformational change in the receptor complex occurs that activates the Jak2/STAT1 signaling cascade. We found that the C-terminal region (amino acids 296-337) of IFNgammaR2 (IFNgammaR2(296-337)) contains a novel Bax inhibitory domain. This portion does not contain the Jak2-binding domain; therefore, the antiapoptotic function of IFNgammaR2 is independent of JAK/STAT signaling. IFNgammaR2(296-337) rescued human cells from apoptosis induced by overexpression of Bax but not Bak. Overexpression of IFNgammaR2 (wild type and IFNgammaR2(296-337)) rescued cells from etoposide and staurosporine, which are known to induce Bax-mediated cell death. Interestingly, IFNgammaR2 inhibited apoptosis induced by the BH3-only protein Bim-EL, suggesting that IFNgammaR2 inhibits Bax activation through a BH3-only protein. Bax and IFNgammaR2 were co-immunoprecipitated from cell lysates prepared from HEK293 and DAMI cells. Furthermore, direct binding of purified recombinant proteins of Bax and IFNgammaR2 was also confirmed. Addition of recombinant Bcl-2 protein to cell lysates significantly reduced the interaction of IFNgammaR2 and Bax, suggesting that Bcl-2 and IFNgammaR2 bind a similar domain of Bax. We found that the C-terminal fragment (cytoplasmic domain) of IFNgammaR2 is expressed in human cancer cell lines of megakaryocytic cancer (DAMI), breast cancer (MDA-MD-468), and prostate cancer (PC3 cells). The presence of the C-terminal fragment of IFNgammaR2 may confer on cancer cells resistance to apoptotic stresses. Our discovery of the anti-Bax activity of the cytoplasmic domain of IFNgammaR2 may shed new light on the mechanism of how cell death is controlled by IFNgamma and Bax.
Gomez
Jose A
JA
Department of Medicine, Division of Hematology/Oncology, Case Western Reserve University, Cleveland, OH 44106 , USA.
Sun
Weiyon
W
Gama
Vivian
V
Hajkova
Dagmar
D
Yoshida
Tomoyuki
T
Wu
Zhengrong
Z
Miyagi
Masaru
M
Pink
John J
JJ
Jackson
Mark W
MW
Danielpour
David
D
Matsuyama
Shigemi
S
D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D000072224:Bcl-2-Like Protein 11; D001665:Binding Sites; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D053614:Janus Kinase 2 / Q000235:genetics / Q000378:metabolism; D013058:Mass Spectrometry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D017471:Receptors, Interferon / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D050794:STAT1 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D015003:Yeasts / Q000235:genetics; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000235:genetics / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism*
D051017:Apoptosis Regulatory Proteins; C000606775:BCL2L11 protein, human; D000072224:Bcl-2-Like Protein 11; C086185:IFNGR2 protein, human; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D017471:Receptors, Interferon; D050794:STAT1 Transcription Factor; C494079:STAT1 protein, human; D050998:bcl-2 Homologous Antagonist-Killer Protein; D051028:bcl-2-Associated X Protein; D049452:Green Fluorescent Proteins; C507924:JAK2 protein, human; D053614:Janus Kinase 2