Expression of αB-crystallin overrides the anti-apoptotic activity of XIAP.
Although crystallins are major structural proteins in the lens, α-crystallins perform non-lens functions, and αB-crystallin has been shown to act as an anti-apoptotic mediator in various cells. The present study was undertaken to examine whether αB-crystallin expressed in human malignant glioma cells exerts anti-apoptotic activity. In addition, we sought to elucidate the mechanism underlying any observed anti-apoptotic function of αB-crystallin in these cells. Three glioma cell lines, U373MG, U118MG, and T98G, were used. We observed that only the U373MG cell line expresses αB-crystallin, whereas the other 2 glioma cell lines, U118MG and T98G, demonstrated no endogenous expression of αB-crystallin. We next observed that the silencing of αB-crystallin sensitized U373MG cells to suberoylanilide hydroxamic acid (SAHA)-induced apoptosis and that αB-crystallin associates with caspase-3 and XIAP. Because XIAP is the most potent suppressor of mammalian apoptosis through the direct binding with caspases, we assessed whether XIAP also plays an anti-apoptotic role in SAHA-induced apoptosis in αB-crystallin-expressing U373MG cells. Of note, the silencing of XIAP did not alter the amount of cell death induced by SAHA, indicating that XIAP does not exert an anti-apoptotic activity in U373MG cells. We then determined whether the ectopic expression of αB-crystallin in glioma cells caused a loss of the anti-apoptotic activity of XIAP. Accordingly, we established 2 αB-crystallin over-expressing glioma cell lines, U118MG and T98G, and found that the silencing of XIAP did not sensitize these cells to SAHA-induced apoptosis. These findings suggest that αB-crystallin expressed in glioma cells overrides the anti-apoptotic activity exerted by XIAP.
Department of Anatomy and Cell Biology and Mitochondria Hub Regulation Center, College of Medicine, Dong-A University, Busan, Republic of Korea.
Jee Suk
JS
Lee
Hye Young
HY
Kim
Na Young
NY
Jeong
Sang Yeob
SY
Lee
Young Geol
YG
Yoon
Yung Hyun
YH
Choi
Chunlan
C
Yan
In-Sun
IS
Chu
Hyungjong
H
Koh
Hwan Tae
HT
Park
Young Hyun
YH
Yoo
D017209:Apoptosis / Q000502:physiology*; D015153:Blotting, Western; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D005910:Glioma / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D018613:Microscopy, Confocal; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism*; D038203:alpha-Crystallin B Chain / Q000378:metabolism*
C059215:CRYAB protein, human; D034741:RNA, Small Interfering; D051636:X-Linked Inhibitor of Apoptosis Protein; D038203:alpha-Crystallin B Chain